Set content preview to null when response fails with exception

[0x1306e6d]

Motivation:

Following the discussion in #6570 (comment), content preview was being generated even when a preceding decorator failed with an exception. This behavior was inconsistent with DefaultRequestLog, which sets the preview to null when an exception is present:

armeria/core/src/main/java/com/linecorp/armeria/common/logging/DefaultRequestLog.java

Lines 1471 to 1473 in d068172

	// Will auto-fill response content and its preview if response has failed.
	deferredFlags = this.deferredFlags & ~(RESPONSE_CONTENT.flag() |
	RESPONSE_CONTENT_PREVIEW.flag());

The content preview should not be recorded when the response flow is interrupted by an exception, as the decorator did not actually process the response content.

Modifications:

• Set responseContentPreview(null) in ContentPreviewingUtil when responseContentPreviewer is null.
• Set responseContentPreview(null) in ContentPreviewingService when service execution throws an exception.
• Updated tests to verify null content preview for various exception scenarios with and without error handlers.

Result:

• Response content preview is properly set to null when exceptions are raised.
• Consistent behavior between decorator-level exceptions and error handler responses.

[coderabbitai]

📝 Walkthrough

Walkthrough

These changes add explicit null logging for response content previews in error scenarios and refactor the error response test suite to use parameterized testing with multiple server configurations for comprehensive behavior verification.

Changes

Cohort / File(s)	Summary
Response Content Preview Logging core/src/main/java/com/linecorp/armeria/internal/logging/ContentPreviewingUtil.java, core/src/main/java/com/linecorp/armeria/server/logging/ContentPreviewingService.java	Added ctx.logBuilder().responseContentPreview(null) calls in two locations: when response previewer is unavailable and in the exception handling path, ensuring null content previews are explicitly logged.
Error Response Test Refactoring core/src/test/java/com/linecorp/armeria/server/logging/ContentPreviewingErrorResponseTest.java	Restructured test infrastructure to support parameterized testing with two ServerExtension instances, introduced centralized configureServer helper method, migrated from ArgumentsProvider to ValueSource, added conditional error handler wiring, and reworked test assertions to verify behavior across error handler presence/absence scenarios.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Poem

🐰 Null previews now logged, oh what a treat,
When errors hop by, responses stay neat,
Tests parameterized, servers now two,
Error handlers dance—with or without their shoe! 🥾

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'Set content preview to null when response fails with exception' is clear, concise, and directly describes the main change: setting content preview to null in exception scenarios.
Description check	✅ Passed	The description comprehensively explains the motivation (inconsistency with DefaultRequestLog), modifications made to three files, and the expected result of the changes.

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✨ Finishing touches

• 📝 Generate docstrings

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📥 Commits

Reviewing files that changed from the base of the PR and between d897515 and 5f16553.

📒 Files selected for processing (3)

• core/src/main/java/com/linecorp/armeria/internal/logging/ContentPreviewingUtil.java
• core/src/main/java/com/linecorp/armeria/server/logging/ContentPreviewingService.java
• core/src/test/java/com/linecorp/armeria/server/logging/ContentPreviewingErrorResponseTest.java

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Files:

• core/src/main/java/com/linecorp/armeria/internal/logging/ContentPreviewingUtil.java
• core/src/main/java/com/linecorp/armeria/server/logging/ContentPreviewingService.java
• core/src/test/java/com/linecorp/armeria/server/logging/ContentPreviewingErrorResponseTest.java

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🔇 Additional comments (7)

core/src/main/java/com/linecorp/armeria/server/logging/ContentPreviewingService.java (1)

178-181: LGTM! Correctly sets null preview when exception occurs.

This ensures the deferred RESPONSE_CONTENT_PREVIEW property is fulfilled when the service throws an exception, maintaining consistency with DefaultRequestLog behavior.

core/src/main/java/com/linecorp/armeria/internal/logging/ContentPreviewingUtil.java (1)

116-120: LGTM! Handles the case where response fails before headers are received.

When responseContentPreviewer is null, it means ResponseHeaders were never received (e.g., HttpResponse.ofFailure() was used). Explicitly setting the preview to null ensures the deferred log property is fulfilled.

core/src/test/java/com/linecorp/armeria/server/logging/ContentPreviewingErrorResponseTest.java (5)

40-54: LGTM! Clean test setup with two server configurations.

The dual server extensions effectively test both scenarios (with and without error handler) while sharing configuration logic via configureServer.

---

56-127: LGTM! Comprehensive server configuration for all failure scenarios.

The configuration covers multiple failure patterns (throw vs. ofFailure) across different route types (direct, annotated, binding) with proper conditional error handler wiring.

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129-175: LGTM! Parameterized tests properly verify null preview for both configurations.

The tests comprehensively cover all failure paths and verify that responseContentPreview is null regardless of whether an error handler is configured.

---

177-192: LGTM! Correctly tests that annotated exception handlers record content preview.

This test validates the expected behavioral difference: annotated service exception handlers produce responses before ContentPreviewingService in the decorator chain, so their responses are previewed normally, unlike server/service-level error handlers.

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194-215: LGTM! Annotated service provides complete test coverage for failure scenarios.

The service properly implements all four combinations of failure patterns for annotated service testing.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.38%. Comparing base (8150425) to head (5f16553).
⚠️ Report is 321 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6589      +/-   ##
============================================
- Coverage     74.46%   74.38%   -0.08%     
- Complexity    22234    23715    +1481     
============================================
  Files          1963     2128     +165     
  Lines         82437    88596    +6159     
  Branches      10764    11585     +821     
============================================
+ Hits          61385    65903    +4518     
- Misses        15918    17159    +1241     
- Partials       5134     5534     +400     

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[github-actions]

🔍 Build Scan® (commit: 5f16553)

Job name	Status	Build Scan®
build-ubicloud-standard-16-jdk-8	✅	https://ge.armeria.dev/s/47vxzfpbpjm2u
build-ubicloud-standard-16-jdk-25	✅	https://ge.armeria.dev/s/yxk2ns6vephbq
build-ubicloud-standard-16-jdk-21-snapshot-blockhound	❌ (failure)	https://ge.armeria.dev/s/4bocwcb3jxa2g
build-ubicloud-standard-16-jdk-17-min-java-17-coverage	✅	https://ge.armeria.dev/s/i6bwzkjznaj7u
build-ubicloud-standard-16-jdk-17-min-java-11	❌ (failure)	https://ge.armeria.dev/s/b44pue5sayrdg
build-ubicloud-standard-16-jdk-17-leak	❌ (failure)	https://ge.armeria.dev/s/6qlhvzpwwl2py
build-ubicloud-standard-16-jdk-11	✅	https://ge.armeria.dev/s/5zkzx26o6zbqe
build-macos-latest-jdk-25	✅	https://ge.armeria.dev/s/zupttsgle72p2

[jrhee17]

👍 👍

[ikhoon]

👍👍