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Serverless Stepfunctions

Implement the AWS Trouble Ticket Step Functions example using the the Serverless Framework and plugin. And we'll switch from Node to Python.

I'm using node v12.2.0. Install serverless woth step functions and AWS pseudo param plugins:

npm install

The serverless app is under slssteps so:

cd slssteps

The package.json installs serverless locally, not globally, so you don't have the binary in your PATH. You could set path or do:

alias sls=../node_modules/.bin/sls

Provide your AWS creds:

export AWS_PROFILE=vstudios

Deploy the lambdas, workflow, other resources:

sls deploy

You can test a function and see its logs:

sls invoke -f hello -l

We have functions mirroring the AWS example:

  • OpenCase
  • AssignCase
  • WorkOnCase
  • EscalateCase
  • CloseCase

We can invoke the OpenCase to test it in isolation, or to start the Step Function state machine once it's defined:

sls invoke -f OpenCase -l -d '{"input_case_id": "42"}'

The state machine is defined in serverless.yml mirroring the AWS example. After we do the sls deploy again, we can test it in the AWS Console and see it works. Run it a few times, so it exercised both the happy path and the failure path.

We can manually invoke the state machine, passing in our data:

sls invoke stepf --name CallCenter -d '{"input_case_id": "Manual SLS STEPF invoke"}'

and it reports the output of the entire machine's execution:

{
  executionArn: 'arn:aws:states:us-east-1:304932368623:execution:CallCenterStepFunctionsStateMachine-UexAbet6E2ow:7801bf4a-199f-44bb-9922-c75fb625d43f',
  stateMachineArn: 'arn:aws:states:us-east-1:304932368623:stateMachine:CallCenterStepFunctionsStateMachine-UexAbet6E2ow',
  name: '7801bf4a-199f-44bb-9922-c75fb625d43f',
  status: 'SUCCEEDED',
  startDate: 2019-06-19T09:34:17.629Z,
  stopDate: 2019-06-19T09:34:18.995Z,
  input: '{"input_case_id": "Manual SLS STEPF invoke"}',
  output: '{"Case": "Manual SLS STEPF invoke", "Message": "Case Manual SLS STEPF ' +
    'invoke: opened... assigned... was resolved...closed.", "Status": 1}'
}

We also added an events stanza in the state machine, specifying an HTTP POST to /opencase. This will trigger the first step defined by the StartAt clause. You can pass event data to it like:

curl https://$URL_FROM_DEPLOYMENT.../dev/opencase -d '{"input_case_id": "My ID"}'

and you can watch the Lambda function logs with the usual tail:

sls logs --function OpenCase --tail &

If you look at the console you can see it flowed through, successfully in this case.