[Lambda] new Segment does not appear when using facade as parent

[bryanvaz]

I'm trying to set the addIncomingRequestData in Lambda. Using this function on the facade Segment does not work, and X-Ray just seems to ignore the additional data:

// Koa middleware
const koaMw = async (ctx, next) => {
  const parent = AWSXRay.getSegment(); // returns the Lambda facade segment
  const segment = parent.addNewSubsegment('Koa');
  parent.addIncomingRequestData(new IncomingRequestData(ctx.req));
  await next(); // Continue Koa request execution
  segment.close();
  parent.http.close();
  // ... Lambda will close the facade segment, so don't worry
}

As an alternative, I thought that if I created a new Segment and using Lambda's facade Segment's trace_id as the parent for the new Segment I could get it to work. Based on the X-Ray docs, I would expect this to create a new node on the service map that would be downstream from the lambda execution. This was even worse because X-Ray just ignored my new Segment completely.

// Koa middleware
const koaMw = async (ctx, next) => {
  const parent = AWSXRay.getSegment(); // returns the Lambda facade segment

  const amznTraceHeader = mwUtils.processHeaders(ctx);
  const segment = new Segment(
      'Koa',
      amznTraceHeader.Root || amznTraceHeader.root,
      parent.trace_id,
    );
  mwUtils.resolveSampling(amznTraceHeader, segment, ctx);
  segment.addIncomingRequestData(new IncomingRequestData(ctx.req));
  await next(); // Continue Koa request execution
  segment.http.close();
  segment.close();
  segment.flush();
  // ... Lambda will close the facade segment, so don't worry
}

Is there anyway to create a new downstream service Segment on service map, separate from the Lambda node?
(I need some way to capture the HTTP request details because HTTP API Gateways do not support X-Ray)

Cheers,
Bryan

[bhautikpip]

Hi Bryan,

I think as reference from here, I believe segments created within lambda function are treated as facade segments hence no operation could be performed using that segment. I believe when you call parent.addIncomingRequestData(new IncomingRequestData(ctx.req)); from within your lambda function SDK treats that function call as no-op.

aws-xray-sdk-node/packages/core/lib/segments/segment.d.ts

Line 17 in c3e7b85

addIncomingRequestData(data: IncomingRequestData): void;

As per your original question this answer would explain better on having separate nodes on X-Ray console when you create segment within your lambda function.

[bryanvaz]

@bhautikpip Yes, I'm aware of the no-op. that's why I thought using the facade as a parent and creating a new Segment would work.
Specifying the lambda facade as a parent should theoretically work, because it is the same thing that happens when you create a sub request to another service. In that scenario, the second service would use the lambda facade trace_id as the parent in order connect it to the same service graph.

As a note, if you create a new Segment without a parent, the node will show up, but without any relation to the lambda initialization and invocation node, which makes the waterfall kind of useless.

[bhautikpip]

right. I think as per my understanding this case would be similar as having Express server deployed to lambda and Express middleware tries to create segment but Lambda facade segment will ignore that and on the X-Ray console you will only see one node AWS::Lambda::Function as being discussed here #45

[stale]

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