Cold start is a term commonly used to describe the Init phase of a Lambda function. In this phase, Lambda creates or unfreezes an execution environment with the configured resources, downloads the code for the function and all layers, initializes any extensions, initializes the runtime, and then runs the function’s initialization code (the code outside the main handler). The Init phase happens either during the first invocation, or in advance of function invocations if you have enabled provisioned concurrency.
To learn more about the Lambda execution environment lifecycle, see the Execution environment section of the AWS Lambda documentation.
As a Powertools user you probably won't be using this class directly, in fact if you use other Powertools utilities the cold start heuristic found here is already used to:
Add a coldStart key to the structured logs when injecting context information in Logger
Emit a metric during a cold start function invocation in Metrics
Annotate the invocation segment with a coldStart key in Tracer
If you want to use this logic in your own utilities, Utility provides two methods:
Since the Utility class is instantiated outside of the Lambda handler it will persist across invocations of the same execution environment. This means that if you call getColdStart() multiple times, it will return true during the first invocation, and false afterwards.
exportconsthandler = async (_event: any, _context: any) => { if (utility.isColdStart()) { // do something, this block is only executed on the first invocation of the function } else { // do something else, this block gets executed on all subsequent invocations } };
Intro
Utility is a base class that other Powertools utilites can extend to inherit shared logic.
Key features
Usage
Cold Start
Cold start is a term commonly used to describe the
Initphase of a Lambda function. In this phase, Lambda creates or unfreezes an execution environment with the configured resources, downloads the code for the function and all layers, initializes any extensions, initializes the runtime, and then runs the function’s initialization code (the code outside the main handler). The Init phase happens either during the first invocation, or in advance of function invocations if you have enabled provisioned concurrency.To learn more about the Lambda execution environment lifecycle, see the Execution environment section of the AWS Lambda documentation.
As a Powertools user you probably won't be using this class directly, in fact if you use other Powertools utilities the cold start heuristic found here is already used to:
coldStartkey to the structured logs when injecting context information inLoggerMetricscoldStartkey inTracerIf you want to use this logic in your own utilities,
Utilityprovides two methods:getColdStart()Since the
Utilityclass is instantiated outside of the Lambda handler it will persist across invocations of the same execution environment. This means that if you callgetColdStart()multiple times, it will returntrueduring the first invocation, andfalseafterwards.isColdStart()This method is an alias of
getColdStart()and is exposed for convenience and better readability in certain usages.