Custom AWS Lambda runtime: provide your own bootstrap

README.md

Custom AWS Lambda runtime: provide your own bootstrap

A runtime is a program that runs a Lambda function's handler method when the function is invoked. The runtime can be included in your function's deployment package, or in a layer. Learn more about custom Lambda runtimes.

For reference, this function includes a sample Bash runtime in bootstrap.sample and a corresponding handler file hello.sh.sample. As a next step, you should provide your own bootstrap by either adding a layer implementing a custom runtime or including a bootstrap file in this function's deployment package.

bootstrap

#!/bin/sh
set -euo pipefail

# Handler format: <script_name>.<bash_function_name>
#
# The script file <script_name>.sh  must be located at the root of your
# function's deployment package, alongside this bootstrap executable.
source $(dirname "$0")/"$(echo $_HANDLER | cut -d. -f1).sh"

while true
do
    # Request the next event from the Lambda runtime
    HEADERS="$(mktemp)"
    EVENT_DATA=$(curl -v -sS -LD "$HEADERS" -X GET "http://${AWS_LAMBDA_RUNTIME_API}/2018-06-01/runtime/invocation/next")
    INVOCATION_ID=$(grep -Fi Lambda-Runtime-Aws-Request-Id "$HEADERS" | tr -d '[:space:]' | cut -d: -f2)

    # Execute the handler function from the script
    RESPONSE=$($(echo "$_HANDLER" | cut -d. -f2) "$EVENT_DATA")

    # Send the response to Lambda runtime
    curl -v -sS -X POST "http://${AWS_LAMBDA_RUNTIME_API}/2018-06-01/runtime/invocation/$INVOCATION_ID/response" -d "$RESPONSE"
done

hello.sh

function handler () {
    EVENT_DATA=$1

    # Show all engironment variables
    printenv

    RESPONSE="{\"statusCode\": 200, \"body\": \"Hello from Lambda!\"}"
    echo $RESPONSE
}