Fix Netty 4.1 server span completion for streaming responses

[ygree]

What Does This Do

Updates Netty 4.1 server instrumentation to keep request spans open until the HTTP response is actually complete.

It tracks pending HTTP/1.1 request contexts in FIFO order, finishes streaming/chunked responses on LastHttpContent, finishes header-complete responses such as 204/205/304, HEAD, CONNECT, Content-Length: 0, and WebSocket upgrades at the response headers, keeps spans open across interim 1xx responses (e.g. 100 Continue, 103 Early Hints), finishes connection-close-delimited responses (no Content-Length, not chunked) normally when the channel closes, and marks a response as an error only when it declared a body that never completed before the channel closed.

Motivation

Netty 4.1 server spans could finish when the first response headers/chunk were written instead of when the response completed. That made streaming response durations too short and could misattribute spans on keep-alive or pipelined HTTP/1.1 connections.

Additional Notes

The fix avoids relying on a single channel-level streaming context because that is not sufficient for pipelined requests. Response writes are matched to the queued request context instead.

Contributor Checklist

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Jira ticket: APMS-20050

[datadog-datadog-prod-us1-2]

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 57.03% (-12.70%)

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[dd-octo-sts]

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	13.97 s	13.95 s	[-0.6%; +0.9%] (no difference)
startup:insecure-bank:tracing:Agent	12.89 s	13.05 s	[-2.0%; -0.4%] (maybe better)
startup:petclinic:appsec:Agent	16.96 s	16.86 s	[-0.5%; +1.8%] (no difference)
startup:petclinic:iast:Agent	16.84 s	16.44 s	[-2.1%; +7.0%] (no difference)
startup:petclinic:profiling:Agent	16.81 s	16.96 s	[-1.9%; +0.2%] (no difference)
startup:petclinic:sca:Agent	16.92 s	16.94 s	[-1.1%; +0.8%] (no difference)
startup:petclinic:tracing:Agent	16.06 s	16.01 s	[-0.6%; +1.2%] (no difference)

Commit: efe71442 · CI Pipeline · Benchmarking Platform UI

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Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.

[datadog-datadog-prod-us1-2]

More details

The PR correctly refactors Netty 4.1 server span lifecycle to keep spans open until response completion instead of finishing on first headers. A FIFO queue ensures pipelined requests match responses correctly, and guards protect against double-finishing. All critical scenarios (chunked responses, bodyless responses, pipelined requests, connection drops) are tested and pass validation. No behavioral regressions found in diff analysis or test coverage review.

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[chatgpt-codex-connector]

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[datadog-datadog-prod-us1-2]

More details

The PR's isTerminalResponse logic was traced through 15 concrete response type/method combinations (FullHttpResponse, chunked, 1xx, 204/205/304, HEAD, CONNECT, WebSocket, close-delimited, Content-Length:0) and the channelInactive handler was verified against 6 channel-close scenarios. No path produces a span leak, a double-reported span under normal conditions, or a misclassified terminal/non-terminal response. The PR also silently fixes two pre-existing bugs: 103 Early Hints was incorrectly treated as terminal in the old code (consuming the one-shot AppSec analysis slot), and Upgrade: WebSocket with a capital W was not recognised as a WebSocket upgrade due to a case-sensitive string comparison.

Was this helpful? React 👍 or 👎

_{📊 Validated against 26 scenarios · Open Bits AI session}

_{🤖 Datadog Autotest · Commit efe7144 · What is Autotest? · Any feedback? Reach out in #autotest}