Serverless development with Go and AWS SAM

A workshop.

brief

The goal is to create a serverless implementaion of the unix command wc, using Go and AWS SAM. Test locally and deploy to AWS. Count words and lines to match the equivalent output of wc -w and wc -l. Build in multiple iterations, testing and deploying at each phase.

disclaimer

If you're using Windows you're gonna have to figure out a bunch of stuff for yourself. The deployment scripts are written in bash.

what you need

• go, prefer 1.11 for module support.
• docker, required for sam local.
• aws cli, installed and configured.
• sam cli, for hopefully obvious reasons.
• curl, or an alternative for testing.

prep

Create an S3 bucket to store the deployment package.

aws s3 mb s3://some-bucket

Clone this repo probably.

git clone https://github.com/dedelala/go-sam-workshop.git
cd go-sam-workshop

If you have Go 1.11 you can clone anywhere, otherwise you will need to use the Go workspace. Version 1.11 is preferable.

template

Create an infrastructure template, template.yml, with a serverless function! The function needs an API event with a root endpoint (/) that accepts POST requests. The template needs a lambda execution IAM role that allows logging. It is helpful for the template to have an output for the resulting API endpoint.

Tip: searching for AWS::Serverless::Function will get you going.

Skip: for the completed template, git checkout step-template.

handler

Write a handler, main.go, that responds with a 200 status (and a message if you like). The main method needs to call lambda.Start with a handler method. The handler method accepts an events.APIGatewayProxyRequest and returns an events.APIGatewayProxyResponse and an error.

Tip: lambda and events are sub-packages of github.com/aws/aws-lambda-go.

Skip: for the completed handler, git checkout step-handler.

local

Write a script that builds the handler and runs it locally. Build a static, linux, amd64 binary named wc to match the template. Use of Go modules is preferred. The binary must be zipped and named wc.zip to match the template. Then run sam local start-api

Skip: for the completed script, git checkout step-local.

Run it!

./local.sh

Test with another prompt.

curl -X POST http://localhost:3000

Stop local.sh with Ctrl+C.

deploy

Write a script that builds the handler, packages and deploys it using sam cli. Accept a bucket name and stack name as parameters. For bonus points the script will check the system for its dependencies. Finally, if the stack template outputs the API endpoint the script should get and print it.

Tip: the build and zip steps are the same as local.sh.

Tip: the relevant sam commands are package and deploy.

Skip: for the completed script, git checkout step-deploy.

Run it!

./deploy.sh <some-bucket> <stack-name>

Test it!

curl -X POST <url-goes-here>

words

Modify the handler to count the number of words in the request body. The response must be json encoded.

# example
curl -X POST --data-binary 'a b c d e f g' http://localhost:3000
# output: {"words":7}

Tip: package unicode is your friend.

Tip: package json is used for json encoding. Producing the result in any other way will be frowned upon.

Skip: for the completed handler, git checkout step-words

Test the changes locally.

./local.sh

Count the words in main.go.

curl -X POST --data-binary @main.go http://localhost:3000

Check the result!

wc -w main.go

Deploy the modified handler and test it live!

lines

Modify the handler to count lines as well as words. Add endpoints to the handler, /words for the word count, /lines for the line count. Have / return both!

Tip: adding endpoints requires modifications to template.yml.

Skip: for the completed handler, git checkout step-lines

Local, test, deploy, test, drop down, increase spead and reverse direction!

congratulations

You made a thing!

clean up

The web console will be sufficient for a quick clean up.

• Delete any Cloudformation stacks that were created.
• Delete the S3 bucket.