As a business owner or operations manager responsible for production, understanding the supply chain is essential to the success of your business. Any obstacle or impediment to upstream and downstream meaning in maths list smooth flow of production can mean thousands of dollars lost and problems with the clients who depend on the delivery of your goods. The manufacturing production process can be pictured like a river.
It's not unusual to hear people involved in production make frequent reference to "upstream" and "downstream" parts of the process. Upstream refers to the material inputs needed for production, while downstream is the opposite end, where products get produced and distributed. Using the metaphor of a river, upstream production refers to all the activities needed to gather the materials required to create a product.
The upstream stage of the production process involves searching for and extracting raw materials. The upstream part of the production process does not do anything with the material itself, such as processing the material. This part of the process simply finds and extracts the raw material. Therefore, any industry that relies on the extraction of raw materials commonly has an upstream stage in its production process.
In a more general sense, "upstream" can also refer to any part of the production process relating to the extraction stages. In this industry, locating underground or underwater oil reserves characterizes the upstream process.
Additionally, the upstream process in petroleum involves bringing oil and gas to the surface. Extraction wells represent an example of a structure operating in this stage in the process. The upstream and downstream meaning in maths list stage in the production process may also manifest itself as a supplier providing raw materials to manufacturers or other businesses that ultimately process the materials.
In contrast, the downstream production process involves processing the materials collected upstream and downstream meaning in maths list the upstream stage into a finished product. The downstream stage further includes the actual sale of that product to other businesses, governments or private individuals.
The type of end user will vary depending on the finished product. Regardless of the industry involved, the downstream process has direct contact with customers through the finished product. The downstream process often includes elements such as distribution, wholesaling and retailing, all of which are involved in ensuring timely delivery to clients. Customer service is also part of the downstream process because it is the final bridge between the product and the end user.
Inefficient customer service can negatively impact the sale of the final product. Staying with the petroleum industry example, the downstream process could consist of converting crude oil into other products and then selling those products to customers.
Thus, oil refineries represent structures that operate within the downstream process. However, any upstream and downstream meaning in maths list of plant that processes raw materials may qualify as operating within the downstream stage of production. In some instances, a company may find it more efficient and cost-effective to combine the downstream and upstream process by controlling all aspects of production. This is known as vertical integration because one management team at one location supervises the upstream and downstream aspects of production.
For example, in the petroleum industry, one company could own a refinery to mine for raw materials and upstream and downstream meaning in maths list processing facility to refine the materials and turn them into petroleum. That company would also own the vehicles necessary to deliver the petroleum to various clients that depend on timely delivery of petroleum for their businesses.
Sampson Quain is an experienced content writer with a wide range of expertise in small business, digital marketing, SEO marketing, SEM marketing, and social media outreach. He has written primarily for the EHow brand of Demand Studios as well as business strategy sites such as Digital Authority. By Sampson Quain Updated February 20, Related Articles.
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The second largest recorded was an 8. Remember this is not linear growth. Based on this the likelihood of an earthquake and tsunami like that happening within the lifetime of the powerplant was incredibly low. Were the earthquake an 8. It is an absurd statement to chock this up to human fault. We're talking about an absurdly rare and freak event, and no one died.
As to the cost of the cleanup which includes tsunami cleanup as well as radiation fwiw , well we could make it a lot cheaper if we reduced the acceptable levels of early death by radiation.
The hard part is that there may or may not be small radioactive particulate on the ground and this could get introduced into water or food getting inside the body. Letting people move back would still likely result in less deaths than coal does per year. I'm not advocating for this, I think that'd be insane, but why is this insane?
Why is pumping out more coal not more insane? What's the difference? We're talking about human lives and livelihood here. When it is more humane to send people back to live in a radioactive zone than keeping coal plants online, maybe we should re-question our priors. What issue are we trying to solve? Because if it is saving human lives we're doing a pretty bang up job.
If it is cost, ditto. If it is climate, ditto. The arguments being made here are often absurd. There is no question that nuclear is clean and safe. The question is about cost, how much you value human life, how much you value carbon, and how much you value pollution. But if you think lives are cheap, climate change isn't real, and not or pollution isn't a big deal, then yeah, continue fighting against nuclear because it is costly.
Why leave out the cost of fossil fuel power sources throughout history? And deaths caused by fossil fuel emissions which is in the tens of thousands per year.
We leave that out because it's irrelevant to whether nuclear or renewables should be used to replace fossil fuels. It is highly relevant, because renewables are not presently capable of replacing fossil fuels. And they won't be until massive energy storage systems, literally thousands of times better than what we have now, is developed.
California, Hawaii, and other places are already hitting saturated electricity markets during the daytime. Companies aren't starting to install storage, as renewable evangelists promised.
Th fact that California only has 1. Who cares if the state met it's storage goals if the storage goals were tiny?
That's not 1. And it's not just about meeting current targets but the rapid pace of new storage coming online. Watts isn't a unit of storage, watts per a unit of time is a unit of storage. That's not actually the key figure of merit, the problem isn't how long stored sources can be used but peak output. All of it for longer than that none of the various utility-scale sources have a discharge that quickly , which is why power and not energy is the thing that is targeted.
But it varies utility-scale battery systems have a different profile [and differing within that by specific battery tech] than thermal storage which has a different profile than pumped hydro, etc.
The concern is the depth of the trough that storage can handle, you need breadth too, so a substantial level of that comes inherently with depth, and the main concern is short-term variation.
That is exactly the problem. Yes, output matter, too, but capacity is the main figure people are interested in. If storage system A can output 1. Basically we're trying to find the area of rectangle. You're providing the height, but staying conspicuously mum about the width. No, the concern is both depth and breadth. It's easy to build a battery system that puts out a lot of energy for a short period of time. It's hard to build a battery system that puts out a lot of energy for 12 hours.
Absolutely none of this changes the undeniable fact that "storage" is incapable of meeting the demands of baseload power generation currently provided by Nuclear and fossil fuels. We aren't anywhere close and won't be for many years which is why it's so absolutely ridiculous how green activists implicitly endorse using coal, natural gas and other fossil fuels which kill tens of thousands of people every year and are cooking the planet, when we have nuclear, which kills no one, and does not contribute substantively to climate change.
It's almost like the activists care more about posturing and magical thinking than they do "saving the planet" So that leaves So again, why are you fear-mongering about how "dangerous" nuclear is when it's a tiny tiny fraction of the real danger of fossil fuels? I thought climate change was like an urgent crisis or something? Stupulous 25 days ago [�]. I think the question is whether renewables should replace nuclear or fossil fuels first. The top level comment isn't talking about replacing fossil fuels with nuclear.
It's literally impossible based on current or any near-term technology. We are being told on the one hand that climate change is an existential threat to tens hundreds? Oh but actually we can just refuse to decarbonize our energy production because maybe someday 10, 20, 50 or years from now there's a true "green" renewable energy I guess.
The top level post recommends doing this only to carbon sources and leaving nuclear alone. There are good arguments for and against pivoting to nuclear right now. But there is an I think unquestionable position presented here that we shouldn't be pivoting away from nuclear and shutting down plants.
It's clear they can, although it's more than just using Li-ion batteries. It'd probably be helpful to elaborate, rather than just insist that the above commenter is wrong and loosely suggest at other solutions.
Things like hydrogen storage, synthetic methane, and thermal storage remain in the prototyping phase. I think it's not correct to say that they can, seeing as there isn't even a commercial market for these technologies let alone one that we know will scale. It's clear than nuclear power can completely replace fossil fuels.
Renewables might be able to replace it, but that's a gamble based on assuming a new storage solution will work excellent. Not just better, but truly blows-everything-else-out-of-the-water phenomenal.
When the stakes at play are stopping climate change, this is a very risky assumption to make. What company can I call up and buy 50 GWh of storage from? That's only 6 minutes worth of storage for the USA. I'd say if we could provision 1 hour's worth of storage over the span of a decade, that'd amount to a demonstration of economic feasibility. But few of these upcoming technologies are making it out of the prototyping stage, let alone commerical success on this scale.
There isn't a company you can call up because projects of this magnitude aren't quoted over the phone to internet forums users. GWh is an incomplete way to specify storage, there are different technologies for the different ways storage may be needed, depending on what resources are on the grid: short term to handle the peaks of everyone microwaving their breakfast and coffee at 7am or long term storage to handle a once every few decades event like a Texas snow storm.
No one is presently making these because the policy of the grid was developed around power plants that dig stuff out of the ground and burn it - the markets are based on bidding with the assumption every power plant will have a marginal cost of generation relative to the cost of its fuel.
This policy doesn't reflect the nature of renewables which besides their capital cost have very low to 0 marginal cost of production. This has disrupted the energy markets in many ways and policy is still being developed to incentivize storage capacity.
The point is that saying "No one is presently making these" on one hand, and claiming that they're within existing industrial capacity is contradictory. Energy markets like Hawaii and California are already hitting situations where energy cost is near zero due to overproduction from intermittent sources.
But the promise that entrepreneurs will store this energy and put it back on the grid later has yet to pan out - contrary to the insistence of storage evangelists, hydrogen storage, synthetic methane, thermal batteries, and whatnot are a lot harder to build than one might think. It's not contradictory. The storage is not being done now not because it's impossible, but because the market conditions that would cause it specifically, high carbon taxes aren't there yet.
Something like pumped thermal storage requires no new technology. It's just putting together things we can already build. I'm glad you can google "energy storage" and click on one of the first links but literally none of these are currently capable of replacing baseload nuclear and fossil fuel energy generation.
You can listen to the people who work in this industry and have studied it deeply or you can keep googling furiously for webpages that support your magical thinking. I didn't "furiously google" anything I "calmly referenced" some of the MANY notes I have from following articles, podcasts, and journals in this field, which I have spent most of my career in.
In fact, I didn't see ANY links from you supporting your nonsense about renewables not working, despite them working in many places across the globe. You have absolutely no idea what you're talking about.
There is no way that renewable energy can replace baseload power generation of FF and natural gas given current technology. All you have is magical thinking and science fiction. No sir, YOU have absolutely no idea what you're talking about.
Note that you are not claiming that they could be competitive, but that they could not do it at all, regardless of price. This is clearly nonsense. Please feel free to point me to any developed country that has successfully replaced fossil fuel and nuclear baseload generation with renewables and energy storage. I'll save you the time. No one has done it. And no, not because evil mustachio-twirling Koch brothers are pulling the strings.
Because the technology does not exist at scale to do this. Or do you want to continue with your speculative science fiction daydreams? The argument you make there is of course invalid. Your argument is "it hasn't happened yet, therefore it cannot happen". This argument proves entirely too much; it implies no technological change can ever occur. To make this argument, you have to demonstrate that the situations in which the change did not occur are the same in all important respects as the current situation.
And you cannot do that. Here's what's different. In the case of PV, by nearly an order of magnitude. This is an extreme rate of change for an energy technology. However, it won't be ripped out until it becomes uneconomical to operate it which means ignoring its capital cost.
So observing that the source are still being used doesn't imply renewables are not winning. Renewables don't have to beat fossil fuels unburdened by CO2 taxes although we may have waited long enough with CO2 taxes that they may increasingly do so, at least in some market conditions. CO2 taxes will rise to the level needed to push fossil fuels entirely out of the market, and then the question becomes "which is cheaper, nuclear or renewables or, possibly, fossil fuels with CCS "?
This and not ludicrous conspiracy theory is why you're seeing massive installation of renewables around the world, and nuclear installs are gasping for breath. WalterBright 26 days ago [�].
It might be far cheaper and practical to just make an "exclusion zone" out of the areas around Fukushima rather than trying to clean them up. While I agree with you that shutting down existing nuclear plants, assuming they're in proper operating condition, is a bad idea vs the urgency of climate change.
But nuclear power has never been the ultra cheap clean power slam dunk you're portraying. I've been hopeful someone will come up with a clever innovation that changes the cost numbers, but so far every attempt has tanked. With hydroelectric dams, there is an urgent motivation to bring many of them down: ecosystem collapse.
It hurts to lose the storage capacity, but there's a growing awareness of just how severe the damage has been. I don't expect Grand Coulee to come down any time soon but talking with someone who does modeling related to this for NOAA made clear a lot of them are going away. Like solar and wind, the vast majority of the cost is the upfront building, and so it costs pennies to operate afterward.
And your comments about hydro dams is just proving my point about climate change just not being a major priority. Local concerns take precedence. It shows how little most people really care, including unfortunately people who ostensibly ought to, like environmental activists and regulators and pro-environmental politicians. I really think Greta Thunberg was right about that. Again, it's just not true that existing nuclear is extremely cheap.
States in the US have recently had to bailout nuclear plant operators because they are struggling to compete against solar, wind, and cheap natural gas see Illinois and Ohio as examples. In the past 10 years, something like 20 plants have been decommissioned for cost reasons.
Now I totally agree that we should keep existing plants running for as long as possible for climate reasons. I am fine with subsidizing them to a certain extent because they produce carbon free power. But even the existing plants are expensive to run and you should acknowledge that instead of saying otherwise I have yet to meet a single climate scientist that is anti-nuclear.
Most of them are shy about their support and will end up saying things like "but we can't get support for nuclear, so why even try? Safety it is number 1 you can see numbers from my other post , emissions lifetime it is on par with solar and wind without batteries , waste isn't as big of an issue as it is made to be waste is magnitudes smaller than most people think and storing on site is perfectly acceptable , it is clearly environmentally friendly low footprint, you can recycle fuel, most emissions are from construction.
The only argument against it is cost. The only argument is that the cost of climate and human lives is low. I'm really frustrated with the misnomers people are making about this.
No, local concerns are not dominating, and I don't think you can read this as some measure of relative prioritization like that. It's too complex to reduce to such a simple imagined dynamic. Understanding that sustainable ecology requires both removing some of these dams and addressing climate change is urgent is in fact possible simultaneously. Then why are existing fossil fuel plants treated as a separate problem to be tackled later?
Greta is right. There are certain things about climate change that are complex. But the lack of sufficient action is not a complex mystery. Greta is right, and also smart in that she focuses her activism on the need for urgency without getting bogged down in advocating for a particular solution. You have very strong expectations that the rest of the world should immediately follow your plans concerning fission.
That's not the same thing, and you will get pushback. Getting pushback does not mean we're somehow evil people that don't prioritize this enough, it just means we disagree with you about the costs and best path forward given pragmatic realities. Not saying I disagree with the sentiment, but I think there are other environmental impacts to consider besides just climate change.
Hydroelectric dams have in many cases destroyed complete ecosystems. There have been case studies of how getting rid of existing hydroelectric dams have revitalized otherwise decimated wildlife populations. Robotbeat 25 days ago [�].
Sure, and maybe there are good arguments for getting rid of nuclear, too. But I want it explained clearly and rationally to me why tackling climate change should be a secondary priority to why it should wait for addressing these other local issues FIRST. Are the hydro dams literally going to be turned off simultaneously the same day with shutting off all connected fossil fuel plants? A big part of why climate change is bad is because it will cause complete ecosystems to collapse.
If dams or anything else accelerate that faster than climate change, there is an argument to be made that they should take higher priority. In the case of the Kennebec River that's exactly what happened. Other than the oft-mentioned risks of nuclear, it is 1 not as cheap as you think and 2 not straightforward to maintain in a warming environment.
Nuclear power is far more expensive than renewables, due to the high costs for construction and dismantling. This does not dismiss your argument, because running a nuclear power plant is fairly cheap. The costs therefore speak towards keeping nuclear power plants running as long as they remain safe.
Existing nuclear power plants use huge quantities of fresh water for cooling. The required water quantity and temperature make nuclear power plants prone to droughts, which can cause shutdowns, and to flooding events, which can shut down or damage the plant. Both droughts and floods are increasing in frequency due to climate change. This speaks towards closing down power plants that are particularly vulnerable.
In any case, grid operators need to be able to mitigate nuclear power plant outages. The cost of nuclear power is even less attractive when overcapacity is needed to accommodate potential outages. My favorites are: Figure 2 - fixed monthly charge showing CA undercharges for fixed infrastructure costs Figure 3 - marginal cost per residential KWh showing CA recoups it in very-high rates Figure 9 - marginal profit over social cost showing CA is super expensive, even post-carbon-tax.
I'm not against solar and wind. We can't afford that time. Statistically speaking, I'd imagine that it's actually the increases in production via wind and solar that has in fact caused nuclear as percentage to fall.
Coal, at least in the USA can't be much different than nuclear. How much nuclear production has come online since i. Now how many solar panels? Given the long lead time of nuclear i. Should nuclear press on regardless?
So little nuclear has come online since partly because of fear-mongering from activists and people for the last 20 years complaining that Nuclear takes too long to build. If only 20 years ago people realized all our climate and energy problems wouldn't be solved and we should build the safest, cleanest and only technology to prevent climate change caused by energy production No, it's because nuclear fell out of the running economically.
In large part this was due to the steady advance in gas turbine and combined cycle power plants. The capital cost of these plants is just incredibly low, times cheaper per kW than a nuclear plant.
If "activists" stopped spending all their time fear-mongering about how expensive, dangerous, and time-consuming nuclear is we could have had massive government subsidies to almost entirely end fossil fuel production for energy!
The "it's all the activist's fault" argument has long since become ludicrous. No, it's because the nuclear lied about how cheap it would be, then failed to execute properly. When precisely did "the nuclear lied"? The cost and timeline estimates for building new reactors at Vogtle and VC Summer were woefully lowballed.
The VC Summer project was ultimately cancelled in , 4 years after construction started, with no reactor completed. Utility executives criminally concealed the dire state of the project before it was cancelled.
After the scheme broke ground in March , it suffered delays and cost overruns. There are no criminal charges I'm aware of in connection with the Vogtle project, but it seems to have been estimated with a similarly ludicrous degree of optimism.
Construction started in March In Georgia Power was telling the public that its new reactors would be operating in and respectively. Vogtle 3 may finally start this year if there aren't further delays. AtlasBarfed 26 days ago [�]. If it costs more money to keep these dinosaurs running than installing solar and wind and batteries to replace natural gas and coal, then In order to replace fossil fuels using wind and storage you would need significant more than 4 hours, using a much slower charge cycle.
If we want to have something like 1 week of storage, with an expected charge cycle of 2 weeks ie one week where the wind is producing more than the grid, followed by one week where it is producing less , we are talking about 42x in capacity, and the investment will get repaid 14x slower for each dollar invested.
Prices will need to drop and production will need to be heavily increased before batteries is viable for wind, and until then more fossil fueled power plants is being built in order to match the capacity of wind.
If I had to choose between battery and nuclear, my choice is neither. Simply ban fossil fuels while we wait for people to make up their mind. If they'd actually try to cash that stock, they'd run out of buyers and the stock price would go way, way down. Solar and wind are great now, because we can pick a random spot and build it without needing storage and don't have many people objecting to it.
Yes, the lawsuits are there already, but so far we've only gotten to the low hanging fruit. The earth has a finite amount of habitable land. If you start filling that up with solar panels, land price will increase because you have to buy it from people that wanted to plant crops there or live there.
A few countries like the USA and Argentina have it easy, but most places don't have large swathes of land laying around completely unused with wind and sun aplenty. We currently use about PWh worldwide, only 27 of which is electricity[1].
We're barely starting to make a dent in electricity production and what you hear left and right is "not in my backyard" and "not on my the neighbor's roof that I have to look at every day" --my dad. We'd barely have the space if people wouldn't complain, let alone if we can only build it away from civilization. And that's replacing electricity production alone, we haven't really started on transportation, making things cement, steel, plastics, What's more: due to only replacing a tiny percentage of electricity production with solar and wind, we aren't yet seeing the need for large scale energy storage, which seems like it will easily triple the cost with current technology my takeaway from [2], p.
You might counter with putting the stuff on sea instead to avoid the finite land issue. The primary problem there is that this is not where people live, increasing the cost of construction, maintenance, and energy transportation.
For example, wind on sea is about as expensive as nuclear I should start keeping notes on which sources I looked at before and copy-paste texts instead of memorize and reiterate. Solar I don't know, but for some reason we're not doing that on the same scale as wind, presumably for a good reason. There just aren't any easy shortcuts here, only compromises.
Let's not dismiss fission energy just yet. Until we have better tech, let's get started with the current tech and hope it becomes obsolete and we get cheaper energy with a sunk cost rather than not try because we might sink some cost. So the objection is that the larger the share of renewable electricity, the higher the electricity price? I'm sure you can see why this is not really a problem?
Because the higher the electricity price the more profitable it becomes to invest in renewable electricity. In fact, what currently is stalling the build-out of renewables in many European markets is that electricity prices have plummeted.
Most countries don't have large uranium deposits either. Importation and exportation solves such problems. The need for large-scale energy storage may not materialize since fluctuations in power production will be matched by fluctuations in power consumption. Most people don't live near nuclear power plants either.
And for offshore wind, costs keep falling while they are stagnant or increasing for nuclear. Then I hope you and like-minded are willing to finance the costs of new nuclear power yourselves, because I don't want my taxpayer money to be wasted on any more nuclear boondoggles.
Rule35 25 days ago [�]. OP is talking about generation costs. Up is bad. To an extent, yes, but uranium doesn't leak out of your rail car the way that electricity is lost when you try to transport it.
The choice is between power lines or converting it with losses in order to have a physical thing, like hydrogen, that can be transported. Statement not found in citation. When I read this last bit, I figured I might as well stop here and regret spending those 20 minutes checking stuff and so indeed I didn't bother checking your costs for offshore wind and the argument about me paying for it - in fact I pay for a lot of shit that other people don't, like Climeworks, because yeah I do actually care and we'll need all the tech we can get.
Morocco and other North African countries are building massive solar farms to export electricity to Europe. Is your claim that the need for large-scale storage will only arise when renewables stand for a large fraction of a country's total energy production?
Currently, most countries have existing large-scale storage and distribution systems for fossil fuel. I imagine that they would need to be replaced with similar systems for electricity if most vehicles switches to electricity.
All recent nuclear projects in the West have been plagued by massive delays and cost overruns: Flamanville, Hinkley Point, Vogtle, and Olkiluoto. Those who have had to foot the bill for these failures are the taxpayers.
At this point, it isn't unfair to ask those who think nuclear power is indispensable to risk their own money, rather than others. What's your opinion of mask refusers? How about people who don't actually refuse to wear a mask but who just sabotage all societal effort to encourage mask wearing? It's easier to import a few tons of Uranium fuel pellets every year than to export terawatts of energy.
I wish we'd just bill fossil fuel plants for their pollution. We'd quickly need new alternatives and instead of us simply telling you that renewables won't work as foreseen you could just run into the problem yourself. I want to add that I and most pro-Nuke people I know also want renewables. In good wind places, wind is a huge win. In good solar places, solar is a huge win. A healthy grid definitely takes advantage of cheap renewables and ideally peakable businesses develop to more effectively utilize variable power.
We just don't think it's appropriate for everything. Renewable isn't free or even non-polluting, it merely means limitless which nuclear effectively is as well. Nuclear was still well ahead in with TWh vs. But if these relative growth rates continue it will take only 3.
But it's a lot harder to build new hydro projects than new wind or solar projects. There is a reason why China is nuclear power plants like crazy. China has significantly reduced its nuclear ambitions over time. Back in it planned to have 86 GW of installed nuclear capacity by It actually reached And in building new solar farms.
And in building new wind farms. China is the world's biggest energy producer, so it is going to lead on a lot of absolute energy measures. China can build reactors cheaper than the West, but it can also build solar farms cheaper than the West.
China is adding output from renewables faster than from nuclear projects. HellDunkel 26 days ago [�]. Retric 25 days ago [�]. HellDunkel 25 days ago [�]. This paints a rather distorted picture. I don't particularly want to defend China, but at least they have contributed to the fundamental "victory" economics of solar being able to challenge natural gas. And yes they are totalitarian, but at least they have some awareness of GHG emissions and are executing on alternative energies and EV and battery production and research.
Solar panels don't need rare earth elements. The rest use electromagnets. And of course there is just the regular mining of all the other resources needed to produce these renewables in the first place which might actually be the bigger problem in terms of scale. Our present use of fossil fuels is vast. The effort required to replace fossil fuels will likewise be vast.
It includes a lot more mining for metals used in electric vehicles, regardless of whether those vehicles are charged by nuclear electricity or by renewables. It appears technically feasible to scale up metal extraction to the necessary level. Metal extraction has negative environmental impacts, but the impacts of continuing to burn fossil fuels are worse. Absolutely agree that we need to move off fossil fuels so that to me is a given.
And you're right that the problem is vast and will require a vast effort. But that is also the central problem. Renewable prices are coming down due to economies of scale and possibly due to externalities not being fully captured in the price my main concern but overall installation at this point is relatively small so it's easy to overlook it because the current prices are so attractive.
So the question becomes do these economies of scale hold as we scale up to the necessary levels to replace fossil fuels and nuclear or is there some inflection point where the cost to the environment becomes too great to ignore before we even get there and we find ourselves needing to scramble to build nuclear? Roboprog 26 days ago [�]. Retric 26 days ago [�]. France is heavily dependent on exporting subsidized electricity generated by nuclear at a loss and importing renewable and fossil fuel generated electricity.
But even with that massive exchange for load balancing they still have excess nuclear generation driving up costs. Just compare capacity factors between US and France to understand the true story. It looks fine on paper, but France was dependent on other EU countries avoiding nuclear.
Actually France nuclear industry is harmed by the current chilliness of the EU, lead by germany, toward nuclear power generation. The problem of capacity factors of french nuclear reactors is caused by excess generation by renewables mostly wind from north sea that cannot be stopped and is sold at quasi negative rates. It's clear when you see the capacity factor has been decreasing for the last decades without much change in the number of reactors online in France.
Capacity factors have been improving in France as they scale back nuclear production from PS: The graph makes it clear why things are improving, their simply cutting back on nuclear.
Its annual exchange sold has always remained positive. If what you say is true then yes, but it doesn't sound logical. Why would the French government take taxpayers' money, put that into nuclear facilities, then sell the surplus to other countries if it's such a clear loss of money?
Wouldn't it be more economical to either have other types of energy production facilities or import the power instead? I'm going to need sources, preferably Wikipedia or something similarly peer-reviewed not a random blog or opinionated organisation , for this to make sense to me. Tade0 26 days ago [�]. Because they've built them to serve peak demand.
Nuclear isn't on demand power like natural gas or hydro. It is consistent like coal, unlike solar or wind , but you can't turn it off when you don't need it! Ideally, you can pair it up with some batteries or pumped hydro to save the power you generate when it isn't in demand. Practically speaking, a nice mix of different sources can cover for each's weaknesses. AstralStorm 26 days ago [�]. It is to a point possible to follow the load with a nuclear power plant by changing moderator setup, but only base load and not peak.
Blocks cannot be easily stopped and started, but they can be throttled enough to handle the changes in demand. It is hour-scale tuning. VistaBrokeMyPC 26 days ago [�]. You absolutely can turn it off when you don't need it. Restarting a reactor takes quite some time even with nuclear power densities.
See "xenon poisoning". Keep in mind that hydropower is extremely disruptive to the water ecosystem up and downstream of the facility, destroying habitats and biodiversity. Definitely not the type of side effects you'd consider OK if it's your mission to combat the effects of climate change Hammershaft 26 days ago [�].
As water becomes more scarce hydro power is also creating geopolitical instability that threatens war. Look at the Ethiopian dam project that threatens to dry out the nile, or Chinese dam projects that threaten to cut off agricultural water to some of the most populated regions in India. With glaciers and mountain snowcaps melting, I'd guess that developing countries would continue to invest in hydrological engineering projects.
They give electricity, yes, but they also help prevent flooding, and provide year-round water for irrigation and cities. The slow spring melt of mountain snow turns into a sudden post-storm flood, if the temperatures are warm enough Nuclear is by far the best by this metric ahead of even solar and wind.
I'm not being hyperbolic when I say some of the remaining spots for hydro threaten the spectre of nuclear war in the future. I'm amazed how few people are aware of this. Hydro seems to also have bad implications for wildlife habitat. Here in the Northwest US, there is a lot of desire to remove some dams to restore salmon habitat. I'm not quite sure if this is because these old dams were built before habitat preservation was a major consideration, or if it's an irreconcilable problem.
The Elwah dam they tore down recently was built long ago before conservation was much of a concern. More to the point: it wasn't really economical to keep such small scale hydro going. The large dams on the Columbia and Snake are fairly safe from being eliminated, even if they do cause some habitat loss.
But the reservoirs provide irrigation that makes it politically inexpedient to take them down. Turning them off while fry are heading downstream ought to help, some. I think with the Snake River, the issue is that the river is used to ship grain on barges for export. If they instead had to use trucking, the prices wouldn't be competitive, and would lead to higher emissions.
They all have fish ladders these days. Not perfect, of course, but there is some effort out into at least. I never understand people who oppose hydropower on an environmental basis. Here is the fact.
A lake made by a hydroelectric dam is not much different from a naturally formed, river fed lake. Different river fed lakes have existed for billions of years. Yes, they fill with silt over time. No, the sky does not fall.
See Stanley Pool for an example of a natural lake fed by a major river, i. The problem in the PNW is that these lakes are bad habitat for our native salmon. The more dams we make, the less habitat there is for the salmon. It's not a matter of "oh we just don't like them on principal.
Everything is interconnected, and it's a really typical technocratic attitude to say that it's fine in isolation. It's just a bunch of fish. Analysis is about reducing everything to components.
And guess what -- it has led us astray here. It turns out in the PNW that salmon are a major part of the food chain for a lot of animals, and our hydropower efforts are suppressing that food chain.
It's also making it really hard to find enough salmon to fish for ourselves. You'll see similar problems with the Colorado River. The Hoover Dam has basically destroyed all the downstream ecosystems that relied on the water to create their living conditions. It's an ecological disaster in slow motion. I've read that salmon swimming upstream and dying are a major provider of nutrients for the upstream ecosystem.
I don't think anyone opposes hydropower due to reservoirs, the concern is lifecycle species like salmon that are born at the headwaters of rivers, live their adult life in the ocean, and return to headwaters to reproduce.
Dams get in the way, and the kill rate of dams even with ladders is enormous. The other big concern I see is access, e. There's another thing that destroys rivers: drying out. Not helped with rising average temperatures On the other hand with enough investment you can build artificial lakes instead.
However, current economy does not value the abovementioned things enough to build artificial lakes. If you compare hydro to nuclear, we can dump nuclear waste in a hole in the middle of the desert that is mostly dead.
All the US nuclear waste fits in a football field at a depth less than 10 yards. Hydro harms living ecosystems with areas far far greater than that required for nuclear waste storage. We are talking about country wide scales. AJ 26 days ago [�]. Dams have a life expectancy of years. Globally, most dams are past their life expectancy. If they don't abruptly fail, then they eventually silt up and become useless. People who decide to build new plants make their decision not from concerns about climate change, but economics.
Building a new nuclear plant would be like building a new coal plant, but worse because by the time it's complete the economics will be even poorer in comparison. Nuclear just doesn't make economic sense on any measure: cost per GW, time to complete, up front cost, regulatory difficulty, etc. So as much a nuclear advocates wish more nuclear plants would be built, unless they want to provide significant subsidies, it's just not going to happen.
For the same reason you don't shop around by finding the highest price you can Energy is energy.. If you want nuclear to happen: 1 Disrupt the nuclear construction contracting process. Until fleet contractors like Bechtel et al are stopped from parasitizing the industry, it's going nowhete due to spiralling costs. There is absolutely no way any commercial power purchase agreement buyer is going to spec nuclear when they can get renewables backed by storage for pennies per kwh [1], both of which have install lead times measured in months versus a decade for nuclear.
Tesla committed to having the Hornsdale Power Reserve built in days or it was free [2]. That is what nuclear is up against. Please don't argue base load; there is no need for base load, only diverse firm dispatchable generation assets [3], robust transmission, and demand response for non-essential industrial loads.
There isn't remotely enough storage available to make wind and solar feasible. To put this in perspective, the world consumes 60 TWh of electricity daily, about 2. We have only a couple GWh of battery storage. Hydroelectric provides more, but that's harder to scale because you need the right geography. Once solar saturates daytime demand, provisioning further solar power doesn't contribute to decarbonization.
This is why nuclear is really the only known path to decarbonization. Maybe we'll figure out scalable ways to provision hundreds of terawatt hours of storage, but we might be waiting a long time. Neither of these articles offers a detailed plan on how this storage will be provisioned.
The second doesn't even mention storage at all, only that Europe has enough wind power to power the whole world. Sure, but that's not very useful if that power isn't delivered when you need it. Create a market that makes it profitable to build storage and encourages price reduction. I like framing the problem in this term. Do we have a realistic plan to built a wind and solar grid under that market?
I don't think so, wind and solar are useful for taking a bite out of natural gas but not actually serving as the backbone of an electrical grid. The amount of storage necessary to decarbonize with wind and solar is not feasible, and essentially amounts to betting on some future invention of a cheap mass energy storage device that works everywhere.
Building four nuclear plants for each existing plant is a lot more achievable of a goal than first building a massive amount of solar and wind, and building extensive HVDC transmission, and building tens of Terawatt hours worth of storage.
The first step in the latter is cheaper than building nuclear, it's the other two steps that are wildly expensive if they're even possible. If we actually enacted a binding rule of zero emissions by people would start building nuclear power plants.
We have methane seeping through thawing permafrost today. We can't delay decarbonizing our energy mix for technologies we haven't even invented yet, let alone mass produced. Yes that is the point, it's basic risk management. Betting the farm on future breakthroughs if you consider climate change to be an existential threat is being on fire and waiting for the fire department because you don't wan't to get your soiled jumping to a pond nearby.
Nuclear is by far the best technology we have today so we should go with it until we have better options in our hand. Cost effective fission and fusion are always 10 years away. EDIT: My comment was made before you edited your comment from "just like cost effective grid scale batteries" to what it is now. The title of biggest battery operator in the state could change hands repeatedly based on the order in which those companies' projects wrap up.
The broader story is that multiple experienced energy investors are converging on Texas simultaneously. The interconnection queue contains more than two dozen batteries that are each larger than megawatts; some go up to , , even megawatts. To put these in perspective, the US consumes GWh of electricity every hour. Of the 23 GWh of existing storage, 20 GWh come in the form of hydroelectricity.
We don't need megawatt hours worth of storage. We don't need gigawatt hours worth of storage. We need terawatt hours worth of storage. Armisael16 26 days ago [�]. Why would an continent-scale entity need days or weeks of power storage? For long-tail adverse events? It's easy to engineer power distribution systems for the average case, but unless we accept occasional brownouts as a cost of doing business, we need to build robustness into our generation fleet.
Some amount of firm generation hydro, gas peaker, nuclear is insurance against correlated failure in the global climate system. At this point, it's better to just keep burning natural gas since combined cycle plants are 1. Hydroelectric is geographically limited, you can just build dams where people need additional power. That leaves nuclear. We already have days or weeks of power storage: natural gas in storage caverns.
We could easily have hydrogen stored in such caverns. The single salt formation near Delta Utah could store enough hydrogen to supply the entire US electricity demand for 30 hours.
Even hours runs hundreds of gigawatts. Spanning a continent only helps wind power and not solar power. Their numbers are talking about enough storage to maintain current usage for half a year. To your second comment: spanning a continent does actually help with solar, since the sun is up at different times on the two coasts - that buys you several extra hours of power each day. Also obstructive weather patterns tend to not reach that far.
The above commenter is posting in terms of battery storage in the MWh range. We would indeed need 6 orders of magnitude larger than this even to just have 1 day's worth of storage.
Hundred megawatt hours vs a dozen Terawatt hours. Part of variability is mostly daily, with the sun going up and down. But both solar and wind are also affected by weather. That requires much more substantial amounts of storage to get the grid through consistent days of reduced production. It says that 3 weeks of power storage would be required in total absence of a serious overhaul in transmission capabilities.
I had assumed that was a clear, if unspoken, assumption when I was discussion continent scale entities. Also, the poster you originally responded to was discussing the literal dozens of installations that singlehandedly meet the MWh mark. HN guidelines require that I assume this was a simple failure of reading comprehension.
Even a much more modest goal of provisioning a single day of storage would entail Dozens of MWh facilities is still in the single digit GWh range. That's six orders of magnitude. And this isn't even taking into account handling heating, industrial use, and all the other forms of tapping into fossil fuel energy besides electricity.
Armisael16 25 days ago [�]. Global daily electricity consumption is 60TWh per day. And that's only Electricity consumption. Total energy consumption is more than TWh per day. The point is that dozens of MWh stations is basically nothing. You'd need millions of these sites to make renewables a feasible primary source of energy. Our current technology is not sufficient to make energy storage available to make grid storage viable. Yes a dozen GWh facilities is 1.
Weeklong disruptions are a thing and would occur in the event of month long plumes from forest fires, major volcanic activity or other long tail natural disasters. Relying on such a tightly coupled national grid as required to deploy that storage is a recipe for disaster in the event of any war or unconventional conflict.
A few shut down transmission lines or stations could cripple entire national economy. Overbuilding completely ignores the very real human and environmental costs of doing so. Rare earths are not very green, forced labor as used by much of the solar industry not very humane.
You are condemning millions today to hypothetical harm to thousands tomorrow. It's insanity. The Tesla giga factory is making 20 gWh per year. And we would need to massively scale up battery production anyway for electric cars in a nuclear scenario.
And remember that those batteries are one of the easiest technologies to deploy. You don't need much more than a grid connection, a substation and a concerete pad.
Yes you're missing the point. Most of that storage is hydro and there's a huge gulf between what's required to cover prolonged lulls in such as weeks as was observed recently in Texas and regularly elsewhere - and to peak shave, regulate frequency, and cover until CCGTs can spin up as we have now.
Until we start getting to the multi-GWh scale it's a nonstarter. Again, you either think climate change is an existential problem in which case relying on magic pixiedust in the future is an absurd, or you don't. There's no two ways about it. I think we disagree about what a future energy grid looks like, and that's okay. I enjoy the conversation regardless! PoignardAzur 26 days ago [�].
That's the joke. Actual experts have studied this. No new, and phasing out existing nuclear. Overprovision renewables and produce carbon neutral synthetic fuels with excess power production. Nuclear will never power chainsaws which many across the world depend on. This is a terrible article. It's basically a single chart showing what I can only assume projected energy demand in the USA for a 5-day period in March, and some dispatch figures between various energy sources, and a couple of random generic infographics.
I can only hope that the linked reports actually address those questions. The associated report does have more details whether or not you agree with them. The article is more of a summary. So that's very much nothing changes in the world except for the energy system And the modeling only allows technologies that are commercial today or that have been demonstrated at large pilot scale today.
So in effect, I think that really sets a pretty high bar because in reality, I would expect a number of those things to change over the next 30 years.
For example, I would expect probably lower population growth than EIA projects and considerably lower demand for energy services and industrial production as a result of a slowing economy. And I would have said that before we have the added effects of the pandemic. So the legacy of this work is in that discussion about feeling like that's the analysis that's needed. Not necessarily understanding what does a carbon tax do on the margin or what to other approaches do sort of in the short term and in the macroeconomic system.
But really understanding how many more widgets do we need and how quickly do they need to be deployed if you don't want to do early retirement. So that context of the questions we're trying to answer really sets up the insights that come from backcasting. So one of the things we think a lot about is stock turnover.
So sort of one of our modeling principles is that we don't do early retirement of any resources except for potentially an electricity supply. So for things like light-duty vehicles or industrial boilers, we really need to understand how long do those resources typically stay online?
And that means if it's a year turnover rate for something like a furnace or maybe it's a year turnover rate for something like an industrial boiler. Buggy optimizations can easily lead to hard-to-debug race conditions under load. The tcpsock:connect method may indicate success despite connection failures such as with Connection Refused errors. However, later attempts to manipulate the cosocket object will fail and return the actual error status message generated by the failed connect operation.
Here is the reason: by design, the global environment has exactly the same lifetime as the Nginx request handler associated with it. Each request handler has its own set of Lua global variables and that is the idea of request isolation.
The Lua module is actually loaded by the first Nginx request handler and is cached by the require built-in in the package. But this global variable will be cleared at the end of the request handler, and every subsequent request handler all has its own clean global environment.
So one will get Lua exception for accessing the nil value. It is therefore highly recommended to always declare such within an appropriate local scope instead. To find all instances of Lua global variables in your Lua code, run the lua-releng tool across all. This tool will guarantee that local variables in the Lua module functions are all declared with the local keyword, otherwise a runtime exception will be thrown.
It prevents undesirable race conditions while accessing such variables. See Data Sharing within an Nginx Worker for the reasons behind this. The ngx. There exists a workaround, however, when the original context does not need to wait for the cosocket results.
That is, creating a zero-delay timer via the ngx. NOTE Following the v0. So the following snippet will not work as expected:.
Alternatively, the regex pattern can be presented as a long-bracketed Lua string literal by encasing it in "long brackets", [[ With this approach, the backslashes are only stripped by the Lua language parser and therefore only need to be escaped once each. Within external script files, PCRE sequences presented as long-bracketed Lua string literals do not require modification.
This means that phases that normally run are skipped, such as the rewrite or access phase. This also means that later phases that are run regardless, e. The changes made in every release of this module are listed in the change logs of the OpenResty bundle:. The order in which these modules are added during configuration is important because the position of any filter module in the filtering chain determines the final output, for example.
The correct adding order is shown above. See also the developer build script for more details on setting up the testing environment. To run a specific test block in a particular test file, add the line ONLY to the test block you want to run, and then use the prove utility to run that.
There are also various testing modes based on mockeagain, valgrind, and etc. Refer to the Test::Nginx documentation for more details for various advanced testing modes. Copyright C , by Xiaozhe Wang chaoslawful chaoslawful gmail. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:.
Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. The basic building blocks of scripting Nginx with Lua are directives. Directives are used to specify when the user Lua code is run and how the result will be used. Below is a diagram showing the order in which directives are executed. This directive is deprecated since the v0.
The resty. Specifying this directive will have no effect. This directive was first introduced in the v0. Enables a buffer of the specified size for capturing all the Nginx error log message data not just those produced by this module or the Nginx http subsystem, but everything without touching files or disks. As a rule of thumb, a 4KB buffer can usually hold about 20 typical error log messages. So do the maths!
This buffer never grows. If it is full, new error log messages will replace the oldest ones in the buffer. This Lua API function will return the captured error log messages and also remove these already read from the global capturing buffer, making room for any new error log data.
For this reason, the user should not configure this buffer to be too big if the user read the buffered error log data fast enough. The user can still choose to set an even higher filtering log level on the fly via the Lua API function errlog. It is worth noting that there is no way to capture the debugging logs without building OpenResty or Nginx with the.
And enabling debugging logs is strongly discouraged in production builds due to high overhead. Deactivate this directive if a default Content-Type response header for Lua request handlers is not desired. Asks the underlying libc runtime library to release its cached free memory back to the operating system every N requests processed by the Nginx core. By default, N is You can configure the request count by using your own numbers.
Smaller numbers mean more frequent releases, which may introduce higher CPU time consumption and smaller memory footprint while larger numbers usually lead to less CPU time overhead and relatively larger memory footprint.
Just tune the number for your own use cases. Configuring the argument to 0 essentially turns off the periodical memory trimming altogether. The current implementation uses an Nginx log phase handler to do the request counting.
By default, only "main requests" count. Note that this directive does not affect the memory allocated by LuaJIT's own allocator based on the mmap system call. With this in place, developers can adopt an edit-and-refresh approach. Please note however, that Lua code written inlined within nginx. Disabling the Lua code cache is strongly discouraged for production use and should only be used during development as it has a significant negative impact on overall performance.
For example, the performance of a "hello world" Lua example can drop by an order of magnitude after disabling the Lua code cache. Specifies the maximum number of entries allowed in the worker process level lua thread object cache.
Specifies the maximum number of entries allowed in the worker process level compiled regex cache. The regular expressions used in ngx.
The default number of entries allowed is and when this limit is reached, new regular expressions will not be cached as if the o option was not specified and there will be one, and only one, warning in the error. If you are using the ngx. Specifies the "match limit" used by the PCRE library when executing the ngx.
To quote the PCRE manpage, "the limit When setting the limit to 0, the default "match limit" when compiling the PCRE library is used.
And this is the default value of this directive. The path string is in standard Lua path form, and ;; can be used to stand for the original search paths. The cpath string is in standard Lua cpath form, and ;; can be used to stand for the original cpath.
NOTE Use of this directive is discouraged following the v0. Usually you can pre-load Lua modules at server start-up by means of this hook and take advantage of modern operating systems' copy-on-write COW optimization. Here is an example for pre-loading Lua modules:. Here is an example for this:.
Because the Lua code in this context runs before Nginx forks its worker processes if any , data or code loaded here will enjoy the Copy-on-write COW feature provided by many operating systems among all the worker processes, thus saving a lot of memory. Do not initialize your own Lua global variables in this context because use of Lua global variables have performance penalties and can lead to global namespace pollution see the Lua Variable Scope section for more details.
You should be very careful about potential security vulnerabilities in your Lua code registered in this context because the Nginx master process is often run under the root account. Runs the specified Lua code upon every Nginx worker process's startup when the master process is enabled.
This hook is often used to create per-worker reoccurring timers via the ngx. Below is an example,. This hook no longer runs in the cache manager and cache loader processes since the v0. Runs the specified Lua code upon every Nginx worker process's exit when the master process is enabled.
When the master process is disabled, this hook will run before the Nginx process exits. This hook is often used to release resources allocated by each worker e. This directive is designed to execute short, fast running code blocks as the Nginx event loop is blocked during code execution. Time consuming code sequences should therefore be avoided. In addition, note that this directive can only write out a value to a single Nginx variable at a time.
However, a workaround is possible using the ngx. All of these directives will run in the same order as they appear in the config file. But special care must be taken for injection attacks. When the Lua code cache is turned on by default , the user code is loaded once at the first request and cached and the Nginx config must be reloaded each time the Lua source file is modified.
The Lua code may make API calls and is executed as a new spawned coroutine in an independent global environment i. Do not use this directive and other content handler directives in the same location. This however carries some risks and is not ordinarily recommended. But be very careful about malicious user inputs and always carefully validate or filter out the user-supplied path components.
So the following will work as expected:. Note that when calling ngx. Here the Lua code ngx. Starting from the v0. Here is an example of overriding a response header or adding one if absent in our Lua header filter:.
The input data chunk is passed via ngx. Before the v0. This will truncate the response body and usually result in incomplete and also invalid responses. The Lua code can pass its own modified version of the input data chunk to the downstream Nginx output body filters by overriding ngx. For example, to transform all the lowercase letters in the response body, we can just write:.
When setting nil or an empty Lua string value to ngx. Likewise, new "eof" flag can also be specified by setting a boolean value to ngx. That is, when the body filter sees a chunk containing the word "hello", then it will set the "eof" flag to true immediately, resulting in truncated but still valid responses.
When the Lua code may change the length of the response body, then it is required to always clear out the Content-Length response header if any in a header filter to enforce streaming output, as in. Note that the following API functions are currently disabled within this context due to the limitations in Nginx output filter's current implementation:.
Nginx output filters may be called multiple times for a single request because response body may be delivered in chunks. Thus, the Lua code specified by in this directive may also run multiple times in the lifetime of a single HTTP request. This does not replace the current access logs, but runs before. Also, the Lua load balancer can work with the standard upstream connection pool mechanism, i.
This Lua code execution context does not support yielding, so Lua APIs that may yield like cosockets and "light threads" are disabled in this context. The Nginx core does not read the client request body by default and if request body data is required, then this directive should be turned on or the ngx. It is recommended however, to use the ngx.
It is particularly useful for setting the SSL certificate chain and the corresponding private key on a per-request basis. It is also useful to load such handshake configurations nonblockingly from the remote for example, with the cosocket API. Another typical use case is to do SSL handshake traffic control nonblockingly in this context, with the help of the lua-resty-limit-traffic readme library, for example.
One can also do interesting things with the SSL handshake requests from the client side, like rejecting old SSL clients using the SSLv3 protocol or even below selectively. Below is a trivial example using the ngx.
See more complicated examples in the ngx. Uncaught Lua exceptions in the user Lua code immediately abort the current SSL session, so does the ngx. This Lua code execution context does support yielding, so Lua APIs that may yield like cosockets, sleeping, and "light threads" are enabled in this context. If you are using the official pre-built packages for OpenResty 1. Similarly, if you are not using the Nginx core shipped with OpenResty 1.
Lua APIs that may yield, like ngx. Please note that TLS session tickets are very different and it is the clients' responsibility to cache the SSL session state when session tickets are used. To easily test this hook locally with a modern web browser, you can temporarily put the following line in your https server block to disable the TLS session ticket support:.
Note that this directive can only be used in the http context starting with the v0. Note that: this directive is only allowed to used in http context from the v0. You can still, however, use the ngx. Shared memory zones are always shared by all the Nginx worker processes in the current Nginx server instance. The hard-coded minimum size is 8KB while the practical minimum size depends on actual user data set some people start with 12KB.
The default time unit is s , i. The default setting is 60s. This setting can be overridden by the settimeout or settimeouts methods.
So even 1 byte buffer size should still work everywhere but the performance could be terrible. Specifies the size limit in terms of connection count for every cosocket connection pool associated with every remote server i. When the connection pool exceeds the available size limit, the least recently used idle connection already in the pool will be closed to make room for the current connection.
Note that the cosocket connection pool is per Nginx worker process rather than per Nginx server instance, so size limit specified here also applies to every single Nginx worker process. This directive controls the default maximal idle time of the connections in the cosocket built-in connection pool. When this timeout reaches, idle connections will be closed and removed from the pool. This setting can be overridden by cosocket objects' setkeepalive method.
If you are already doing proper error handling and logging in your Lua code, then it is recommended to turn this directive off to prevent data flushing in your Nginx error log files which is usually rather expensive. The ciphers are specified in the format understood by the OpenSSL library.
The support for the TLSv1. Enables or disables automatic response buffering for HTTP 1. This buffering mechanism is mainly used for HTTP 1. If the Lua code explicitly sets a Content-Length response header before sending the headers either explicitly via ngx.
To output very large response data in a streaming fashion via the ngx. By default, this directive is turned off and the Lua code is postponed to run at the end of the rewrite phase. By default, this directive is turned off and the Lua code is postponed to run at the end of the access phase. According to the current implementation, however, if the client closes the connection before the Lua code finishes reading the request body data via ngx.
Instead, the reading operation on ngx. When TCP keepalive is disabled, it is relying on the client side to close the socket gracefully by sending a FIN packet or something like that. For soft real-time web applications, it is highly recommended to configure the TCP keepalive support in your system's TCP stack implementation in order to detect "half-open" TCP connections in time.
For example, on Linux, you can configure the standard listen directive in your nginx. When exceeding this limit, the ngx. The Nginx Lua API described below can only be called within the user Lua code run in the context of these configuration directives. The API is exposed to Lua in the form of two standard packages ngx and ndk. Use of the package. Disk operations with relatively small amount of data can be done using the standard Lua io library but huge file reading and writing should be avoided wherever possible as they may block the Nginx process significantly.
The data chunk and "eof" flag passed to the downstream Nginx output filters can also be overridden by assigning values directly to the corresponding table elements. Setting ngx. So when you need to read from an Nginx variable repeatedly in your Lua code, cache the Nginx variable value to your own Lua variable, for example,.
Another way of caching the result is to use the ngx. Undefined Nginx variables are evaluated to nil while uninitialized but defined Nginx variables are evaluated to an empty Lua string. This API requires a relatively expensive metamethod call and it is recommended to avoid using it on hot code paths.
OK , ngx. ERROR , and ngx. This constant was first introduced in the v0. These constants are usually used in ngx. Writes argument values into the Nginx error. Lua nil arguments are accepted and result in literal "nil" strings while Lua booleans result in literal "true" or "false" strings.
And the ngx. There is a hard coded byte limitation on error message lengths in the Nginx core. This limit includes trailing newlines and leading time stamps. If the message size exceeds this limit, Nginx will truncate the message text accordingly. This table can be used to store per-request Lua context data and has a life time identical to the current request as with the Nginx variables.
That is, the ngx. Here, modification of the ngx. This is because they have two separate versions of ngx. Internal redirection will destroy the original request ngx. Since dev , the ngx. Note that overwrite values in ngx. Arbitrary data values, including Lua closures and nested tables, can be inserted into this "magic" table.
It also allows the registration of custom meta methods. So do not abuse this API for saving your own function arguments because it usually has quite some performance impact. Because of the metamethod magic, never "local" the ngx. For example, the following is bad:. Everything works internally, efficiently, on the C level.
You should always read the request body by either calling ngx. This API function as well as ngx. Thus, you should use cosockets and streaming processing instead if you have to handle large subrequest responses. Returns a Lua table with 4 slots: res. For multi-value response headers, the value is a Lua array table that holds all the values in the order that they appear. For instance, if the subrequest response headers contain the following lines:.
Then res. You always need to check the res. The data truncation here can only be caused by those unrecoverable errors in your subrequests like the cases that the remote end aborts the connection prematurely in the middle of the response body data stream or a read timeout happens when your subrequest is receiving the response body data from the remote.
Named locations like foo are not allowed due to a limitation in the Nginx core. Use normal locations combined with the internal directive to prepare internal-only locations. The method option is ngx. The format for the Lua table passed as the args argument is identical to the format used in the ngx. If this option is set to true , then the current request and associated subrequests will share the same Nginx variable scope.
Hence, changes to Nginx variables made by a subrequest will affect the current request. Care should be taken in using this option as variable scope sharing can have unexpected side effects. Changes made to these variables by such subrequests will not affect the parent request or any other subrequests sharing the parent request's variables.
In addition to the two settings above, it is possible to specify values for variables in the subrequest using the vars option. These variables are set after the sharing or copying of variables has been evaluated, and provides a more efficient method of passing specific values to a subrequest over encoding them as URL arguments and unescaping them in the Nginx config file.
The ctx option can be used to specify a custom Lua table to serve as the ngx. It is also possible to use this ctx option to share the same ngx. Note that subrequests issued by ngx. There is a hard-coded upper limit on the number of subrequests possible for every main request. In older versions of Nginx, the limit was 50 concurrent subrequests and in more recent versions, Nginx 1.
When this limit is exceeded, the following error message is added to the error. Please also refer to restrictions on capturing locations configured by subrequest directives of other modules. Just like ngx. This function issues several parallel subrequests specified by the input table and returns their results in the same order. This function will not return until all the subrequests terminate.
The total latency is the longest latency of the individual subrequests rather than the sum. Lua tables can be used for both requests and responses when the number of subrequests to be issued is not known in advance:.
Logically speaking, the ngx. Read and write the current request's response status. This should be called before sending out the response headers. Only Lua tables are accepted Only the last element in the table will take effect for standard headers such as Content-Type that only accept a single value. Reading ngx. If the response header is not present at all, nil will be returned.
For multi-value headers, all of the values of header will be collected in order and returned as a Lua table. For example, response headers. Note that ngx. For reading request headers, use the ngx. This function has the same signature as ngx.
Note that a maximum of response headers are parsed by default including those with the same name and that additional response headers are silently discarded to guard against potential denial of service attacks.
Since v0. Returns a boolean indicating whether the current request is an "internal request", i. Returns a floating-point number representing the timestamp including milliseconds as the decimal part when the current request was created. Current possible values are 2.
Returns nil for unrecognized values. By default, the request line and trailing CR LF terminator will also be included. Retrieves the current request's request method name. If the current request is an Nginx subrequest, then the subrequest's method name will be returned. Currently only numerical method constants are supported, like ngx. Rewrite the current request's parsed URI by the uri argument. The uri argument must be a Lua string and cannot be of zero length, or a Lua exception will be thrown.
Location jump will not be triggered otherwise, and only the current request's URI will be modified, which is also the default behavior.
This function will return but with no returned values when the jump argument is false or absent altogether. Use of jump in other contexts is prohibited and will throw out a Lua exception.
Note: this function throws a Lua error if the uri argument contains unsafe characters control characters. Note that it is not possible to use this interface to rewrite URI arguments and that ngx. For instance, Nginx config. Starting from 0. Rewrite the current request's URI query arguments by the args argument.
The args argument can be either a Lua string, as in. In the former case, i. In the latter case, this method will escape argument keys and values according to the URI escaping rule. Multiple occurrences of an argument key will result in a table value holding all the values for that key in order. Keys and values are unescaped according to URI escaping rules. That is, they will take Lua boolean values true. However, they are different from arguments taking empty string values.
Empty key arguments are discarded. Note that a maximum of request arguments are parsed by default including those with the same name and that additional request arguments are silently discarded to guard against potential denial of service attacks. This argument can be set to zero to remove the limit and to process all request arguments received:. Call ngx. Multiple occurrences of an argument key will result in a table value holding all of the values for that key in order.
Note that the ngx. Note that a maximum of request headers are parsed by default including those with the same name and that additional request headers are silently discarded to guard against potential denial of service attacks. This argument can be set to zero to remove the limit and to process all request headers received:.
Since the 0. For example, if a request header My-Foo-Header is present, then the following invocations will all pick up the value of this header correctly:. By default, all the subrequests subsequently initiated by ngx.
None of the current request's existing subrequests will be affected but subsequently initiated subrequests will inherit the change by default. If the request body has already been explicitly discarded, either by the ngx. In case of errors, such as connection errors while reading the data, this method will throw out a Lua exception or terminate the current request with a status code immediately.
The request body data read using this function can be retrieved later via ngx. This depends on. In cases where current request may have a request body and the request body data is not required, The ngx. Explicitly discard the request body, i.
Retrieves in-memory request body data. It returns a Lua string rather than a Lua table holding all the parsed query arguments. Use the ngx. If the request body has not been read yet, call ngx. This is not recommended however. If the request body has been read into disk files, try calling the ngx.
Note that calling this function instead of using ngx. Retrieves the file name for the in-file request body data. Returns nil if the request body has not been read or has been read into memory.
The returned file is read only and is usually cleaned up by Nginx's memory pool. It should not be manually modified, renamed, or removed in Lua code. If the request body has been read into memory, try calling the ngx. Set the current request's request body using the in-memory data specified by the data argument. Additionally, the request body must not have been previously discarded by ngx.
Whether the previous request body has been read into memory or buffered into a disk file, it will be freed or the disk file will be cleaned up immediately, respectively. Creates a new blank request body for the current request and inializes the buffer for later request body data writing via the ngx. When the data can no longer be hold in the memory buffer for the request body, then the data will be flushed onto a temporary file just like the standard request body reader in the Nginx core.
It is important to always call the ngx. Also, when this function is used together with ngx. This function can be used with ngx. Completes the construction process of the new request body created by the ngx. Returns a read-only cosocket object that wraps the downstream connection. Only receive , receiveany and receiveuntil methods are supported on this object. The socket object returned by this method is usually used to read the current request's body in a streaming fashion.
If any request body data has been pre-read into the Nginx core request header buffer, the resulting cosocket object will take care of this to avoid potential data loss resulting from such pre-reading.
Chunked request bodies are not yet supported in this API. Since the v0. When this argument is true , this function returns a full-duplex cosocket object wrapping around the raw downstream connection socket, upon which you can call the receive , receiveany , receiveuntil , and send methods. When the raw argument is true , it is required that no pending data from any previous ngx. So if you have these downstream output calls previously, you should call ngx.
If the request body has not been read yet, then this "raw socket" can also be used to read the request body. You can use the "raw request socket" returned by ngx. You can refer to the lua-resty-websocket library for a real world example.
The optional second args can be used to specify extra URI query arguments, for example:. Named locations are also supported but the second args argument will be ignored if present and the querystring for the new target is inherited from the referring location if any. Also note that this method call terminates the processing of the current request and that it must be called before ngx.
It is recommended that a coding style that combines this method call with the return statement, i. The optional status parameter specifies the HTTP status code to be used. The following status codes are supported right now:.
Here is an example assuming the current server name is localhost and that it is listening on port Note that this method call terminates the processing of the current request and that it must be called before ngx.
Emits arguments concatenated to the HTTP client as response body. If response headers have not been sent, this function will send headers out first and then output body data. Lua nil values will output "nil" strings and Lua boolean values will output "true" and "false" literal strings respectively. This is an asynchronous call and will return immediately without waiting for all the data to be written into the system send buffer.
To run in synchronous mode, call ngx. This can be particularly useful for streaming output. See ngx. Please note that both ngx. So be careful when calling either of these two in a tight loop; buffer the data yourself in Lua and save the calls. Lua nil arguments are accepted and result in literal "nil" string while Lua booleans result in literal "true" or "false" string outputs.
ERR and ngx. Check out Nginx log level constants for details. When called with the default argument, it issues an asynchronous call Returns immediately without waiting for output data to be written into the system send buffer. Calling the function with the wait argument set to true switches to synchronous mode. Note that using the Lua coroutine mechanism means that this function does not block the Nginx event loop even in the synchronous mode.
When ngx. See HTTP 1. The status argument can be ngx. ERROR , ngx. Note that while this method accepts all HTTP status constants as input, it only accepts ngx. OK and ngx. ERROR of the core constants. Also note that this method call terminates the processing of the current request and that it is recommended that a coding style that combines this method call with the return statement, i. This behavior may change in future and it is recommended that users always use return in combination as suggested above.
Explicitly specify the end of the response output stream. In the case of HTTP 1. When you disable the HTTP 1. This trick can be used do back-ground jobs without letting the HTTP clients to wait on the connection, as in the following example:. But if you create subrequests to access other locations configured by Nginx upstream modules, then you should configure those upstream modules to ignore client connection abortions if they are not by default.
Sleeps for the specified seconds without blocking. One can specify time resolution up to 0. It accepts the following values defaults to 2 :. Also, characters that should not appear in escaped string are simply left unchanged.
Multi-value query args are also supported. Just use a Lua table for the argument's value, for example:. If the argument value is false , then the effect is equivalent to the nil value. Decodes a URI encoded query-string into a Lua table. This is the inverse function of ngx. By default, a maximum of request arguments are parsed including those with the same name and that additional URI arguments are silently discarded to guard against potential denial of service attacks.
Decodes the str argument as a base64 digest to the raw form. Returns nil if str is not well formed. This method performs better on relatively short str inputs i.
The result is exactly the same as ngx. This method performs better on relatively long str inputs i. This function requires SHA-1 support in the Nginx build.
Returns current date in the format yyyy-mm-dd from the Nginx cached time no syscall involved unlike Lua's date library.
Returns the elapsed seconds from the epoch for the current time stamp from the Nginx cached time no syscall involved unlike Lua's date library. Updates of the Nginx time cache can be forced by calling ngx. Returns a floating-point number for the elapsed time in seconds including milliseconds as the decimal part from the epoch for the current time stamp from the Nginx cached time no syscall involved unlike Lua's date library.
You can forcibly update the Nginx time cache by calling ngx. Forcibly updates the Nginx current time cache. This call involves a syscall and thus has some overhead, so do not abuse it.
Returns the current time stamp in the format yyyy-mm-dd hh:mm:ss of the Nginx cached time no syscall involved unlike Lua's os. Returns a formatted string can be used as the cookie expiration time. The parameter sec is the time stamp in seconds like those returned from ngx. Returns a formated string can be used as the http header time for example, being used in Last-Modified header. Parse the http time string as returned by ngx.
Returns the seconds or nil if the input string is in bad forms. Returns true if the current request is an Nginx subrequest, or false otherwise. Matches the subject string using the Perl compatible regular expression regex with the optional options. Only the first occurrence of the match is returned, or nil if no match is found. In case of errors, like seeing a bad regular expression or exceeding the PCRE stack limit, nil and a string describing the error will be returned.
When a match is found, a Lua table captures is returned, where captures[0] holds the whole substring being matched, and captures[1] holds the first parenthesized sub-pattern's capturing, captures[2] the second, and so on. Named captures are also supported since the v0.
Unmatched subpatterns will have false values in their captures table fields. Specify options to control how the match operation will be performed. The following option characters are supported:. The o option is useful for performance tuning, because the regex pattern in question will only be compiled once, cached in the worker-process level, and shared among all requests in the current Nginx worker process.
The optional fourth argument, ctx , can be a Lua table holding an optional pos field. When the pos field in the ctx table argument is specified, ngx.
Regardless of the presence of the pos field in the ctx table, ngx. When match fails, the ctx table will be left intact. The ctx table argument combined with the a regex modifier can be used to construct a lexer atop ngx. Note that, the options argument is not optional when the ctx argument is specified and that the empty Lua string "" must be used as placeholder for options if no meaningful regex options are required.
Starting from the 0. This is very useful for recycling Lua tables and saving GC and table allocation overhead. Similar to ngx.
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