[agocs]

What does this PR do?

Updates the trace propagation format for aws-sdk direct lambda invocations. The old way was:

clientContext: {
  custom:{
    _datadog: {
      x-datadog-trace-id: "",
      x-datadog-parent-id: "",
      ...
    }
  }
}

New way is:

clientContext: {
  custom: {
      x-datadog-trace-id: "",
      x-datadog-parent-id: "",
      ...
  }
}

I've added a configuration option called invokeWithLegacyContext (default false) that causes aws-sdk.invoke operations to use the legacy trace propagagtion format. I'm not sure where to document the versions of datadog-lambda-py and datadog-lambda-js that are compatible with the new format.

Reasoning

The Go and Java runtimes only support ClientContext.custom fields of type map[string]string. C.f. :

• Custom client context parser error aws/aws-lambda-java-libs#212
• AWS lambda plugin custom context breaking with aws-lambda-java #1312

In order to pass trace contexts to directly invoked Go and Java lambda functions, we can write the trace context key:values to ClientContext.custom rather than creating a ClientContext.custom._datadog object like we've been doing.

Backwards compatibility

This is, strictly speaking, a breaking change in how we add trace context to direct invocations. The Python and JS repos have already been updated to accept the new format:

• Check for the new direct invocation trace format and use that datadog-lambda-js#194
• Check for the new direct invocation trace format and use that datadog-lambda-python#146

They both check for the old and new formats.

Plugin Checklist

• Unit tests.
• TypeScript definitions.
• TypeScript tests.
• API documentation.
• CircleCI jobs/workflows.
• Plugin is exported.

Additional Notes

[codecov]

Codecov Report

Merging #1506 (5b2f63c) into master (ae2cc0b) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1506      +/-   ##
==========================================
- Coverage   94.18%   94.17%   -0.01%     
==========================================
  Files         157      157              
  Lines        6409     6406       -3     
==========================================
- Hits         6036     6033       -3     
  Misses        373      373              

Impacted Files	Coverage Δ
packages/datadog-plugin-aws-sdk/src/index.js	100.00% <ø> (ø)
...ages/datadog-plugin-aws-sdk/src/services/lambda.js	90.90% <100.00%> (-1.10%)	⬇️

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[bengl]

LGTM, but I think it might be semver-major. Maybe we can default to the "legacy" way now, and save changing the default for an upcoming major rev?

@rochdev what do you think?

[agocs]

Hey @bengl , I flipped invokeWithLegacyContext such that it defaults true. Once this is merged, should I queue up another PR to flip it back, tagged with the 2.0.0 milestone?

[agocs]

Per our conversation on Slack, I've pulled out the invokeWithLegacyContext option because the old way can crash Java and Go lambda functions, but the worst that's going to happen the new way is that an older version of datadog-lambda-python or datadog-lambda-js won't be able to find the trace context.

[agocs]

Hm, it looks like Codecov doesn't like that I decreased the overall line count. Is this a blocker?

[rochdev]

Hm, it looks like Codecov doesn't like that I decreased the overall line count. Is this a blocker?

Not a blocker.