Extract trace context from ALB multiValueHeaders #647
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purple4reina
approved these changes
Apr 29, 2025
duncanista
reviewed
Apr 29, 2025
| @@ -97,6 +97,35 @@ describe("HTTPEventTraceExtractor", () => { | |||
| expect(traceContext?.source).toBe("event"); | |||
| }); | |||
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| it("extracts trace context from payload with multiValueHeaders", () => { | |||
| mockSpanContext = { | |||
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Could you add an event from either ALB or API GW with real values to ensure this works? That way we can re-use it in Bottlecap too
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Just commenting for visibility -- as discussed, this change only applies to ALB. API GW can have multiValueHeaders, but trace context is always injected under the regular headers so no changes needed for API GW
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But I added a real event from ALB!
BridgeAR
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Apr 30, 2025
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duncanista
reviewed
May 5, 2025
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| 8000 if (Array.isArray(val)) { | ||
| // MultiValueHeaders: take the first value | ||
| lowerCaseHeaders[key.toLowerCase()] = val[0] ?? ""; | ||
| } else if (typeof val === "string") { | ||
| // Single‐value header | ||
| lowerCaseHeaders[key.toLowerCase()] = val; | ||
| } |
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Suggested change
| if (Array.isArray(val)) { | |
| // MultiValueHeaders: take the first value | |
| lowerCaseHeaders[key.toLowerCase()] = val[0] ?? ""; | |
| } else if (typeof val === "string") { | |
| // Single‐value header | |
| lowerCaseHeaders[key.toLowerCase()] = val; | |
| } | |
| if (Array.isArray(val)) { | |
| // MultiValueHeaders: take the first value | |
| lowerCaseHeaders[key.toLowerCase()] = val[0] ?? ""; | |
| continue; | |
| } | |
| // Single‐value header | |
| lowerCaseHeaders[key.toLowerCase()] = val; | |
| } |
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We have to type check key and make sure it's a string first; otherwise typescript errors TS2322: Type unknown is not assignable to type string
duncanista
approved these changes
May 5, 2025
nhulston
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May 5, 2025
### What Support trace extraction when we receive `multiValueHeaders` instead of `headers`. This can happen if multi value headers are turned on in ALB. We do this by creating an ALB event in `span_inferrer` -- even though there's no inferred spans, this is still a common event type. The event payload structure for multiValueHeaders is defined here: https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html This also has the benefit of creating these trigger tags: <img width="400" alt="Screenshot 2025-05-01 at 4 55 34 PM" src="https://github.com/user-attachments/assets/d02ba864-3ee3-43d8-9f4b-bdb6650544a5" /> <img width="250" alt="Screenshot 2025-05-01 at 4 56 38 PM" src="https://github.com/user-attachments/assets/15c56afe-d314-4c42-a828-908d499ab62f" /> ### Motivation Porting DataDog/datadog-lambda-js#647 and DataDog/datadog-agent#31542 https://datadoghq.atlassian.net/browse/SVLS-6757
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What does this PR do?
Support trace extraction when we receive
multiValueHeadersinstead ofheaders. This can happen if multi value headers are turned on in ALB.The event payload structure for multiValueHeaders is defined here: https://docs.aws.amazon.com/elasticloadbalancing/latest/application/lambda-functions.html
Motivation
#603
https://datadoghq.atlassian.net/browse/SVLS-6725
Testing Guidelines
Manually, unit tests
Additional Notes
Types of Changes
Check all that apply