sam local start-lambda - AWS Serverless Application Model
UsageOptionsExample

sam local start-lambda

This page provides reference information for the AWS Serverless Application Model Command Line Interface (AWS SAM CLI) sam local start-lambda subcommand.

The sam local start-lambda subcommand starts a local endpoint to emulate AWS Lambda.

Usage

$ sam local start-lambda <options>

Options

--add-host LIST

Passes a hostname to IP address mapping to the Docker container's host file. This parameter can be passed multiple times.

Example: --add-host example.com:127.0.0.1

--beta-features | --no-beta-features

Allow or deny beta features.

--config-env TEXT

The environment name specifying the default parameter values in the configuration file to use. The default value is "default". For more information about configuration files, see AWS SAM CLI configuration file.

--config-file PATH

The path and file name of the configuration file containing default parameter values to use. The default value is "samconfig.toml" in the root of the project directory. For more information about configuration files, see AWS SAM CLI configuration file.

--container-env-vars

Optional. Pass environment variables to image container when locally debugging.

--container-host TEXT

Host of locally emulated Lambda container. The default value is localhost. If you want to run AWS SAM CLI in a Docker container on macOS, you can specify host.docker.internal. If you want to run the container on a different host than AWS SAM CLI, you can specify the IP address of the remote host.

--container-host-interface TEXT

The IP address of the host network interface that container ports should bind to. The default value is 127.0.0.1. Use 0.0.0.0 to bind to all interfaces.

--debug

Turns on debug logging to print debug message generated by the AWS SAM CLI and display timestamps.

--debug-args TEXT

Additional arguments to be passed to the debugger.

--debug-function

Optional. Specifies the Lambda function to apply debug options to when --warm-containers is specified. This parameter applies to --debug-port, --debugger-path, and --debug-args.

--debug-port, -d TEXT

When specified, starts the Lambda function container in debug mode, and exposes this port on the local host.

--debugger-path TEXT

The host path to a debugger to be mounted into the Lambda container.

--docker-network TEXT

The name or ID of an existing Docker network that Lambda Docker containers should connect to, along with the default bridge network. If this is specified, the Lambda containers only connect to the default bridge Docker network.

--docker-volume-basedir, -v TEXT

The location of the base directory where the AWS SAM file exists. If Docker is running on a remote machine, you must mount the path where the AWS SAM file exists on the Docker machine, and modify this value to match the remote machine.

--env-vars, -n PATH

The JSON file that contains values for the Lambda function's environment variables.

--force-image-build

Specify whether the CLI should rebuild the image used for invoking functions with layers.

--help

Shows this message and exits.

--hook-name TEXT

The name of the hook that is used to extend AWS SAM CLI functionality.

Accepted values: terraform.

--host TEXT

The local hostname or IP address to bind to (default: '127.0.0.1').

--invoke-image TEXT

The URI of the container image that you want to use for the local function invocation. By default, AWS SAM pulls the container image from Amazon ECR Public. Use this option to pull the image from another location.

For example, sam local start-lambda MyFunction --invoke-image amazon/aws-sam-cli-emulation-image-python3.8.

--layer-cache-basedir DIRECTORY

Specifies the location basedir where the layers your template uses are downloaded to.

--log-file, -l TEXT

The log file to send runtime logs to.

--no-memory-limit

Removes the memory limitation in the container during local invoke, even when memory is configured in the AWS SAM template.

--parameter-overrides

A string that contains AWS CloudFormation parameter overrides encoded as key-value pairs. Use the same format as the AWS Command Line Interface (AWS CLI). The AWS SAM CLI format is explicit key and value keywords, each override is separated by a space. Here are two examples:

  • --parameter-overrides ParameterKey=hello,ParameterValue=world

  • --parameter-overrides ParameterKey=hello,ParameterValue=world ParameterKey=example1,ParameterValue=example2 ParameterKey=apple,ParameterValue=banana

--port, -p INTEGER

The local port number to listen on (default: '3001').

--profile TEXT

The specific profile from your credential file that gets AWS credentials.

--region TEXT

The AWS Region to deploy to. For example, us-east-1.

--save-params

Save the parameters that you provide at the command line to the AWS SAM configuration file.

--shutdown

Emulates a shutdown event after the invoke completes, in order to test extension handling of shutdown behavior.

--skip-prepare-infra

Skips the preparation stage if no infrastructure changes have been made. Use with the --hook-name option.

--skip-pull-image

Specifies whether the CLI should skip pulling down the latest Docker image for the Lambda runtime.

--template, -t PATH

The AWS SAM template file.

Note

If you specify this option, AWS SAM loads only the template and the local resources that it points to. This option is not compatible with --hook-name.

--terraform-plan-file

The relative or absolute path to your local Terraform plan file when using the AWS SAM CLI with Terraform Cloud. This option requires that --hook-name be set to terraform.

--warm-containers [EAGER | LAZY]

Optional. Specifies how AWS SAM CLI manages containers for each function.

Two options are available:

  • EAGER: Containers for all functions are loaded at startup and persist between invocations.

  • LAZY: Containers are only loaded when each function is first invoked. Those containers persist for additional invocations.

Example

For a detailed example and in-depth walkthrough on using the sam local start-lambda subcommand, refer to Introduction to testing with sam local start-lambda.