lambda-local

This is a tool to run AWS Lambda locally and keep warm. The original perpose is for local testing AWS Lambda more effecient.

NOTE:

• This program is only for test if Lambda function logic correct without deploy. It doesn't provide full feature of cloud version Lambdas.
• It has limited features which only match my work requirement. Anyone intested in it can make a fork and add yourself.

Requitements

• go 1.12 or above for build your own image
• docker v2.0.0.0 or above
• You need to setup valid credentials in ~/.aws/credentials file.

Limits

• Only support Lambdas written in Go with AWS Go Library
• Lambdas should be defined in AWS SAM yaml file
• Same Lambda can only be invoked in a queue no matter the request side is concurrent or not.

Install

It's a web service running in docker container. You can run a shell script to setup/start the container. Full example file is under example/start-lambda.sh. You need to cover those steps to start the container correctly.

1. Download docker image

   docker pull vreal/lambda-local-go
   

2. Create a container from this image. The command is just an example, You can create your own version. The /var/lambdas/main can take multiple -p options to override the yaml template parameters. HostEnv and CacheHost are just example which may not necessary in your own projects. -e AWS_DEFAULT_PROFILE=default is necessary if you are not using default AWS credentials profile.

   docker create -v ~/.aws:/root/.aws --rm -p $PORT:3001/tcp --name $CONTAINER_NAME --network $NETWORK \
   -e AWS_DEFAULT_PROFILE=default -e OTHER_ENV_VARIABLE=$other_variable \
   vreal/lambda-local-go:latest \
   /var/lambdas/main -p HostEnv=$HOST_ENV -p CacheHost=$CACHE_HOST
   

3. Copy template file to /var/lambdas/template.yaml:

   docker cp $TEMPLATE_FILE $CONTAINER_NAME:/var/lambdas/template.yaml
   

4. Copy env json file to /var/lambdas/env.json if exists:

   if [ -z "$ENV_JSON" ]
   then
   docker cp $ENV_JSON $CONTAINER_NAME:/var/lambdas/env.json
   fi
   

5. Copy lambda zip files to /var/lambdas

   for f in $LAMBDA_ZIP_FILES
   do
       echo "UPLOAD "$f
       docker cp $f $CONTAINER_NAME:/var/lambdas 
   done
   

6. Start container. The example turned on the attach to print the logs for debugging. You can turn it off if you don't need to see the logs.

   docker start --attach $CONTAINER_NAME
   

The first request of specified Lambda is a little bit slow but the second time will be faster.