This is an example of the Saga Pattern using AWS Step Functions with Lambda, and AWS CDK for defining the Saga pattern step function state machine and flow.
This CDK app consists of a bunch of simple, example lambda functions that define an imaginery transaction / flow, where a set of records are written to a DynamoDB table with the following steps process:
- Process
- Transform
- Commit
There are 3 x main lambda functions, one for each of the above, and a paired 'rollback' function for each of these in case of failure.
In the event of a failure at a certain point in the transaction, the rollback step for that function will run, followed by the rollback functions for any other steps in the transaction that had already run.
See: Blog post discussing Saga Pattern and this aws-cdk app here.
There is no top-level npm script to build all the lib/lambda function modules, so remember to tsc and npm install for each of those if you wish work with the functions locally. You'll need to do this in the lib/lambda/common directory first, as this is a dependency of each lambda function.
Otherwise, a cdk deploy after a npm run build should be fine to deploy everything as the lambda runtime environment will already contain the npm dependencies (aws-sdk).
Note: CDK deploy will fail if you have run npm install locally for all lambda functions due to the asset package size limit with all node_modules directories in each. There is a better way to deploy all of this and package up the lambda handlers, but for this quick example repository, this is how I've done it.
npm run buildcompile typescript to jsnpm run watchwatch for changes and compilenpm run testperform the jest unit testscdk deploydeploy this stack to your default AWS account/regioncdk diffcompare deployed stack with current statecdk synthemits the synthesized CloudFormation template