perf(html-report): stream report JSON through pooled chunks and overlap sidecar serialization - #6860
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…ap sidecar serialization Cuts the default-on HTML reporter's teardown cost on large suites without changing report content (sidecar JSON byte-identical, embedded HTML payload byte-identical after gzip+base64 decode). - Add SegmentedBufferWriter (pooled, append-only IBufferWriter<byte>). Both the sidecar serializer and the HTML renderer JSON now write into it instead of Utf8JsonWriter -> MemoryStream (grow-and-copy) -> ToArray / GetString. Sidecar files are streamed chunk by chunk (AtomicFile/ReportAggregator overloads); the renderer JSON is gzipped straight from UTF-8 chunks, never materialized as a 22MB UTF-16 string or re-encoded. - Serialize the sidecar on another core while the HTML is generated and written; reuse it when the GitHub integration returns no artifact URL, otherwise re-serialize with the URL as before. - Pick the gzip level by runtime: on .NET 9+ (zlib-ng) Optimal is ~2x faster and ~3% smaller than SmallestSize for report JSON; .NET 8 keeps SmallestSize. - ActivityCollector: per-trace spans kept in a small locked list instead of a ConcurrentQueue per test; tags/events/links read via Activity's struct Enumerate* APIs instead of LINQ ToArray. - Cache the assembly name tag on the test-case span instead of calling Assembly.GetName() per test. 10k trivial tests (net10.0): process allocations 461MB -> 289MB; post-session reporter time ~810ms -> ~580ms (median); HTML report 1.94MB -> 1.88MB.
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Navigate logical layers of code changes, visualize relationships, and explore their blast radius. 📝 WalkthroughWalkthroughThe change adds pooled segmented buffers for report serialization and streaming output. It overlaps sidecar serialization with HTML generation. It also updates trace span storage and caches assembly name lookups. ChangesSegmented reporting output
Trace collection updates
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~30 minutes Change: Refactor Sequence Diagram(s)sequenceDiagram
participant HtmlReporter
participant HtmlReportGenerator
participant SegmentedBufferWriter
participant AtomicFile
HtmlReporter->>SegmentedBufferWriter: Serialize report data
HtmlReporter->>HtmlReportGenerator: Generate HTML
HtmlReportGenerator->>SegmentedBufferWriter: Compress segmented JSON
HtmlReporter->>AtomicFile: Write sidecar buffer
AtomicFile->>SegmentedBufferWriter: Stream chunks to file
Merge Risk: 🟡 Moderate · up to A failed atomic replacement can cause a completed test suite to disappear from aggregation. Remove the in-place fallback before merging. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 21.95% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 41 functions across 9 files. (1 skipped: 1 unsupported.)
✨ Finishing Touches 💡 1📝 Generate docstrings 💡
🧪 Generate unit tests (beta)
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Code reviewReviewed the report-generation allocation/perf work ( No high-confidence bugs found. The trickiest part of this PR — overlapping sidecar serialization with HTML generation while both read the same mutable
One non-blocking observation, not raised as an issue: No compile checks or test runs were performed in this review pass (sandboxed environment); this is a static read of the diff and surrounding code, cross-checked against the reference assemblies where the correctness question depended on it. |
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Actionable comments posted: 1
- 🪄 Fix CodeRabbit comments on this PR
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In `@src/TUnit.Engine/Reporters/Aggregation/AtomicFile.cs`:
- Line 31: Update the fallback after TrySwap in the AtomicFile write flow to
throw an IOException instead of calling WriteBuffer on the destination path.
Preserve the temporary-file write and successful TrySwap behavior, and ensure a
failed atomic replacement does not publish the sidecar in place.
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📒 Files selected for processing (10)
src/TUnit.Engine/Reporters/Aggregation/AtomicFile.cssrc/TUnit.Engine/Reporters/Aggregation/ReportAggregator.cssrc/TUnit.Engine/Reporters/Aggregation/ReportDataJson.cssrc/TUnit.Engine/Reporters/Aggregation/SegmentedBufferWriter.cssrc/TUnit.Engine/Reporters/Html/ActivityCollector.cssrc/TUnit.Engine/Reporters/Html/HtmlReportGenerator.cssrc/TUnit.Engine/Reporters/Html/HtmlReporter.cssrc/TUnit.Engine/TestExecutor.cssrc/TUnit.Reporting.Tool/TUnit.Reporting.Tool.csprojtests/TUnit.UnitTests/SegmentedBufferWriterTests.cs
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Summary
The HTML reporter and JSON sidecar are on by default, so every run pays for them. Profiling a 10,000-test suite (the
Bareshape from meziantou's framework benchmark) put the reporter at ~318 MB allocated and ~800 ms of work after the session ends. That work is inside the process wall clock the benchmark measures.Where the cost went:
ReportDataJson.SerializeToByteswrote into anArrayBufferWriterthat grew by doubling and copying (~68 MB ofbyte[]). It then flushed into aMemoryStreamthat also grows, and finally calledToArray(), which copied the ~20 MB payload once more.HtmlReportGeneratorfollowed the same growth pattern. It then decoded the whole JSON into a ~22 MB UTF-16 string, only to re-encode it for gzip + base64.ConcurrentQueueper test plus LINQToArrayover tags, events and links.Changes:
SegmentedBufferWriter: a new append-onlyIBufferWriter<byte>backed by pooled 256 KB chunks that are never resized or copied. Both JSON outputs write into it.byte[]versions of the write methods remain for existing callers and tests.Optimalis about 2× faster thanSmallestSizeon this payload and about 3% smaller, so it is used there. .NET 8 keepsSmallestSize, where it is 8% smaller. The choice is made at runtime.ActivityCollector: each trace's spans go into a small locked list. Tags, events and links are read without LINQ.TestExecutor: caches the assembly name used for the test-case span instead of callingAssembly.GetName()per test.Report content is unchanged:
Benchmark
10,000 passing tests, net10.0, default reporters. Medians of 9 interleaved runs, measured with a
ProcessExithook so the post-session reporter work is included:Measured alone:
Tests
SegmentedBufferWriterTests(6 tests).TUnit.UnitTests: report aggregation tests andHtmlReporterTruncateOutputTestspass.TUnit.Engine.Tests:HtmlReporterTests(43),HtmlReporterConfigurationTests(22),HtmlReportCliTests,DefaultHtmlReportCliTestsandReportingSettingsTestspass.TUnit.OpenTelemetry.Tests(42) andTUnit.TestProject.HtmlReportDefaultspass.TUnit.Reporting.Toolbuilds.Serializing in parallel keeps both buffers alive at the same time, about 11 MB more than serializing one after the other. That is still far below the baseline.
Summary by CodeRabbit
Performance
Bug Fixes