02_create_a_lambda

Step 2 Create-a-Lambda

Now that you've set up your AWS account and can create lambdas it's time to create one. In it's simplest form a Hello World Lambda example:

exports.handler = (event, context, callback) => {
    callback(null, 'hello world');
};

While this could be copy and pasted into the AWS Lambda Console we are going to make it a little bit more complex to show how you would update a non-trivial lambda.

Prepare the files on your machine

• In the /webhook-lambda directory...
• npm install to install dependencies
• Take a look at the initial state of the webhook All this does is reply back successfully to an API Gateway. It unnecessarily relies on a dependency so you can see how to include dependencies in a lambda by zipping up your node_modules directory.
• zip up the contents of the directory including node_modules into webhook-lambda.zip
  • zip -r ../webhook-lambda.zip *
  • Make sure the files are in the root level of the zip and not one level deep. Otherwise you will get errors like "Cannot find module '/var/task/index'"
  • AWS calls this a "Deployment Package." It has all the files and dependencies necessary, but tells nothing about where or how to deploy the Lambda
• NOTE This response format for responding to an API Gateway (HTTP / rest endpoint for a lambda) was hard to track down: https://aws.amazon.com/premiumsupport/knowledge-center/malformed-502-api-gateway/

Create lambda

• Go to Lambda home page and "Create a Function"
  • Give it a name and choose Node.js 6.10
  • For Role either "Create a Custom Role" and accept the defaults in the window that pops up or head over to IAM and create a new role with the Trusted Entity "Lambda" and the policy "AWSLambdaBasicExecutionRole".
  • Click "Create Function"
• Under the "Function Code" setup block select "Code entry type" then "Upload a .ZIP file" and upload your code.
• The function is created but it's not ready yet. On the next page add "API Gateway" trigger
• Enter API name and deployment stage (I did LambdaMicroService/Prod), change "Security" to "Open". Click "Add"
• On the API Gateway settings you will see that it is listening for any method (GET/POST/PUT/etc) and the Invoke URL is the path to get to your webhook. Test it by hitting it directly:

curl -X POST -H \ "Content-Type: application/json" -d '{ "data": "hello" }' "https://uco290nvi0.execute-api.us-east-1.amazonaws.com/prod/webhook-lambda"

TODO: Later (CLI mode is still a work in progress, skip it for now)

This is a work in progress

aws lambda create-function \
 --function-name webhook \
 --runtime nodejs6.10 \
 --role arn:aws:iam::005155365294:role/webhooklambdarole \
 --handler index.handler \
 --description "A webhook run in a lambda" \
 --publish \
 --zip-file fileb://<path-to-your-zip>/webhook-lambda.zip \

• role is a role you've created from IAM with the Trusted Entity "Lambda" and the policy "AWSLambdaBasicExecutionRole". Copy the "Role ARN"
• You should now see the new Lambda on your list

Make REST API out of lambda

#TODO: This can be done with the CLI, but I'm not sure how

Next proceed to step 3