You will see this in CloudWatch logs, or at the command line if you invoke a function from there. Here is an example of the output after a cold start. But it is generally in the order of a few hundred milliseconds to a couple of seconds. How long a cold start takes varies depending on the size of the application and your initialization code. If requests stop entirely, the pool will shrink to zero after some period of time, and the next invocation will cause a cold start. Over time the pool will grow and shrink as the rate of incoming requests changes. It is possible that through normal use of the Lambda function, you will have a pool of warm execution environments available to handle incoming requests and all requests will be handled by these execution environments. If that was the only execution environment available, then a cold start will occur on the next invocation. If you have a single execution environment warm, and it is handling a request, then a second request to the function will cause a new execution environment to be created, this second execution environment will now go through a cold start.Įven if an execution environment is warm and being called regularly, it will be recycled by the Lambda service at some point. The function will remain warm if it is being called regularly.Īn execution environment will be reused for subsequent invocations of the same function.īut an execution environment can handle a single request at a time.
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The initialization code will not be run again, only the function handler will be run. Once this execution environment is up and running the function is referred to as “warm”, and it will stay warm for an undefined period. The initialization code is run only once for an execution environment, that’s why it’s a good idea to put things like database connection initialization, S3 client creation, etc, outside the function handler. This all happens in response to the first invocation of the function, but before the function handler is run. Initialization code refers to the constructor, initializers, etc. The application is downloaded, memory is allocated, the application is JITed, and the initialization code is run. Creating this environment takes a bit of time and is referred to as a “cold start”. The first time a Lambda function is invoked, an execution environment is created. Scenarios where cold starts may be a problem.Scenarios where cold starts may not be a problem.In the rest of this post I’m going to cover: If you want your Lambda function to be invoked by other AWS services, it is as simple as subscribing to the events they raise. Compare the price of running an application on a server 24/7 vs running it on Lambda only as requests are received. This can be a very efficient way to host such applications. Many people use Lambda functions to host ASP.NET Web API applications. You don’t need to manage any infrastructure, you focus on writing the code, and the Lambda service takes care of provisioning, scaling, and managing the execution environments. You only pay for what you use, so they can be a cost-effective way to run applications that do not need to be up 24/7. They are a great way to run code in response to events from other applications, AWS services, HTTP requests, direct invocations, and polling. The AWS Lambda service is function as a service offering for your. If cold starts are taking too long, or occur more frequently than you would like, there are things you can do to mitigate the problem. If that’s the case, there is nothing to stop you from moving some of your.
So cold starts, may not be a problem at all. Yes, Lambda functions will have cold starts, but they are probably not as frequent as you think or take as long as you think.
From what I’ve seen there seems to be more concern than is warranted. NET with Lambda functions and their cold starts. There is a lot of discussion and opinions around using. It is more of a suggestion that cold starts may not be the problem you think they are, why that’s the case, and some advice on alleviating the problem if it exists.
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This post does not have any hard and fast rules for how you should build your functions, or how to handle cold starts. The advice here should all be viewed in the light of the wonderful hedge - “it depends”.
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