Blog post: Exploring Serverless with Python, StepFunctions, and Web Front-end Serverless

This time, with Serverless framework

This is a 'take two' on Slack Signup with AWS Lambda. It was simple and functional, but working with AWS raw is such a pain in the butt...

Here, I use 1) serverless.com to make working with lambda enjoyable and 2) AWS step-functions for multi-step sign-up workflow that touches multiple services. In this particular example, the workflow does what StackStorm signtup needs:

• call Slack API to create an invitation with Slack's undocumented API
• add a user to ActiveCampaign CRM
• record a user in DynamoDB

It is easy to modify to add your custom steps, have fun!

1. Clone this repository.

2. Install serverless framework, and the required plugins:

   npm install -g serverless
   npm install
   

   I use serverless-stepfunction plugin to write stepfunction as YAML in serverless.yaml and expose it as an API endpoint, and serverless-apig-s3 for convenient front-end deployment to the same URI (no CORS messing).

3. Configure credentials

   1. For AWS credentials, follow setup docs. I prefer using [AWS CLI with named profiles](http://docs.aws.amazon.com/cli/latest/userguide/ cli-multiple-profiles.html). To use an AWS profile, export AWS_DEFAULT_PROFILE="profileName". Test AWS CLI settings: aws lambda list-functions.

      To use an AWS profile in Serverless, export AWS_PROFILE=$AWS_DEFAULT_PROFILE, to match aws CLI profile and avoid confusion. You MUST also specify the AWS region in AWS_REGION for serverless, as it won't take it from AWS profile. So, three env vars in total:

      export AWS_DEFAULT_PROFILE="profileName"
      export AWS_PROFILE=$AWS_DEFAULT_PROFILE
      export AWS_REGION=us-west-2
      

      NOTE: Till the bug #3947 fixed,the way to set a region is by --region in sls CLI.

      Or use --aws-profile profileName when invoking sls CLI. Unfortunately there's no way to test it before you try to deploy.

      Create ./private.yml file and set up the accountID and region there, see private.yml.example. Note that region must match

   2. Slack and ActiveCampaign: place your credentials and config in ./env.yml, use env.yml.example. To find your Slack credentials for production or testing, use this hint from Stackstorm-Exchange.

4. Deploy

   1. Install Python dependencies:

      ./build.sh
      

   2. Deploy serverless stack

      sls deploy -v
      

   3. Deploy web client

      sls client deploy
      

5. Run, with curl:

   curl -X POST -H "Content-Type: application/json" -d '{"email":"[email protected]", "first_name":"Donald", "last_name":"Trump"}'  https://wqftmz3m97.execute-api.us-east-1.amazonaws.com/dev/signup
   

   Or, with serverless, for convenience:

   sls invoke stepf --name signup --data '{"email":"[email protected]", "first_name":"Donald", "last_name":"Trump"}' 
   

1. Run tox (dah, tox and all your Python stack needs to be installed)

   virtualenv .venv
   source .venv/bin/activate
   pip install -r tests/test_requirements.txt
   

2. To run unit tests for local testing/development:

   # Activate virtualenv from tox
   source ./tox/py27/bin/activate
   # Run all tests
   python -m pytest
   # Run a single test and print the output ( -s flag ) 
   python -m pytest -s tests/invite_slack_test.py::InviteSlackTest::test_handler_ok 
   

• Call individual lambda functions with serverless

  sls invoke -f RecordAC --data '{"email":"[email protected]", "first_name":"Donald", "last_name":"Trump"}' 
  

• Watch the logs:

  sls logs -f RecordAC
  

• On subsequent web client updates, just run sls client deploy. However when changes touch API Gateway settings, the full deploy is needed.

• Web updates doesn't [always, ever] deploy the API Gateway changes. Need to deploy manually (Console->Resources->Actions-Deploy API).

• Due to apig-s3 bug, remove the web s3 bucket manually when removing a stack. aws s3 rb s3://bucketname --force

• Removing the stack does not remove the DynamoDB table. If you really want to start from scratch, delete it manually (export the data first): aws dynamodb delete-table --table-name slack-signup-dev