test.md

Testing the Lambda Docker images

The test-function subcommand can pass the correct parameters to docker run to run those images with the payload and environment variables set up correctly. If you would like more control, like mounting volumes, or adding more environment variables this guide describes how to directly run these images using:

docker run

An example of a valid test-function command would look as follows:

fn lambda test-function user/my-function --payload='{"firstName":"John", "lastName":"Yo" }'

Payload

The payload is passed via stdin. It is also possible to pass the payload by using the payload argument. Using it the payload is written to a random, opaque directory on the host. The file itself is called payload.json. This directory is mapped to the /mnt volume in the container, so that the payload is available in /mnt/payload.json. This is not REQUIRED, since the actual runtimes use the PAYLOAD_FILE environment variable to discover the payload location.

Environment variables

The TASK_ID variable maps to the AWS Request ID. This should be set to something unique (a UUID, or an incrementing number).

test-function runs a container with 300MB memory allocated to it. This same information is available inside the container in the TASK_MAXRAM variable. This value can be a number in bytes, or a number suffixed by b, k, m, g for bytes, kilobytes, megabytes and gigabytes respectively. These are case-insensitive.

The following variables are set for AWS compatibility:

• AWS_LAMBDA_FUNCTION_NAME - The name of the docker image.
• AWS_LAMBDA_FUNCTION_VERSION - The default is $LATEST, but any string is allowed.
• AWS_ACCESS_KEY_ID - Set this to the Access Key to allow the Lambda function to use AWS APIs.
• AWS_SECRET_ACCESS_KEY - Set this to the Secret Key to allow the Lambda function to use AWS APIs.

Running the container

The default test-function can then be approximated as the following docker run command:

mkdir /tmp/payload_dir
echo "<payload>" |
docker run -v /tmp/payload_dir:/mnt \
           -m 1G \
           -e TASK_ID=$RANDOM \
           -e TASK_MAXRAM=1G \
           -e AWS_LAMBDA_FUNCTION_NAME=user/fancyfunction \
           -e AWS_LAMBDA_FUNCTION_VERSION=1.0 \
           -e AWS_ACCESS_KEY_ID=<access key> \
           -e AWS_SECRET_ACCESS_KEY=<secret key> \
           --rm -it
           user/fancyfunction