AWS Lambda Concepts

Internal

• AWS Lambda

Function Name

If no name is specified when the function is declared, a name will be generated. If a name is specified, no updates that require replacement of this function can be performed. The only updates that can be performed are those that require no or some interruption. To replace the function, a new name must be specified.

Code

AWS Lambda Function Code

It represents the code for the lambda function. The code for all runtimes can be specified by the location of the deployment package, as an S3 location. For Node.js and Python, the code can be specified in-line. The code specification is required. To update the code, the function requires no interruption. However, changes to a deployment package in Amazon S3 are not detected automatically. To update the function code, the object key can be changed, or use object versioning and change the version number in the template.

Runtime

AWS Lambda Runtimes

The runtime specifies the programming language for the function. A required configuration parameter. Requires no interruption on update.

Execution Environment

Lambda Execution Environment and Available Libraries

When a function is invoked, AWS Lambda attempts to re-use the execution environment from a previous invocation, if one is available. This saves time preparing the execution environment, and allows to save resources like database connections and temporary files in the execution context.

Execution Context

AWS Lambda Execution Context

The execution context is a temporary runtime environment that initializes any external dependencies of the Lambda function code, such as database connections or HTTP endpoints. Setting up the execution context is known as "bootstrapping", which is a process that takes some time and consequently introduces latency in the lambda function execution. After a Lambda function is executed, AWS Lambda maintains the execution context for some time - the context is "frozen" after the execution completes, and its thawed for reuse. This approach has the following implications:

• Any declaration in the function code - outside the handler code - remains initialized. For example, if a function establishes a database connection, the original connection is used in subsequent invocations.
• Each execution context provides 512MB of additional disk space in the /tmp directory. The directory content remains when the execution context is frozen, providing transient cache that can be sued for multiple invocations.
• Background processes or callbacks initiated by the function that did not complete when the function ended resume if the execution context is reused.

Action

Actions

Invoke

Invoke

The function-invoking action of the Lambda service.

It may serve as integration endpoint for Amazon API Gateway Lambda function integration.