feat: [Step Function] Subscribe forwarder to log group

[lym953]

What does this PR do?

Enables adding a subscription filter to subscribe the forwarder to the state machine's log group.

Motivation

This is the second step of instrumenting a step function.

Testing Guidelines

Automated testing

Passed the added test for forwarder setup

Manual testing

Step:

1. Deploy the example stacks in step-functions-typescript-stack.

Result:

1. The subscription filter appeared in AWS UI

@DylanLovesCoffee sorry I borrowed your forwarder.

Additional Notes

It takes a lot of code to extract log group from the log config of a state machine, if the user sets the log group themselves.

      // Extract log group from logging config
      const destinations = cfnStateMachine.loggingConfiguration.destinations;
      if (!this.isLogDestinationPropertyArray(destinations)) {
        throw new Error("destinations is not an array");
      }

      const destination = destinations[0];
      if (!("cloudWatchLogsLogGroup" in destination)) {
        throw new Error("cloudWatchLogsLogGroup is not in destination");
      }

      const logGroupConfig = destination.cloudWatchLogsLogGroup;
      if (logGroupConfig === undefined) {
        throw new Error("cloudWatchLogsLogGroup is undefined");
      }

      if (!("logGroupArn" in logGroupConfig)) {
        throw new Error("logGroupArn is not in cloudWatchLogsLogGroup");
      }

      const logGroupArn = logGroupConfig.logGroupArn;
      if (logGroupArn === undefined) {
        throw new Error("logGroupArn is undefined");
      }

      logGroup = logs.LogGroup.fromLogGroupArn(this, "LogGroup", logGroupArn);

There are so many checks because at each level, the variable can often have multiple possible types, e.g. logGroupConfig can be

IResolvable | sfn.CfnStateMachine.CloudWatchLogsLogGroupProperty | undefined

To be able to parse the log group, we assume that nothing is an unresolved token (i.e. IResolvable), and throw if anything is an unresolved token. I'm not sure in what case and if it's common that anything is an unresolved token. I think we can start from handling the simple case, and come back later if anyone asks for supporting the unresolved token cases.

Types of Changes

• [ ] Bug fix
• [x] New feature
• [ ] Breaking change
• [ ] Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• [ ] This PR's description is comprehensive
• [ ] This PR contains breaking changes that are documented in the description
• [ ] This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• [ ] This PR impacts documentation, and it has been updated (or a ticket has been logged)
• [ ] This PR's changes are covered by the automated tests
• [ ] This PR collects user input/sensitive content into Datadog

[lym953]

/merge

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2024-11-07 15:44:07 UTC :information_source: MergeQueue: pull request added to the queue

The median merge time in main is 8m.