Fix directIO reader hang when pread returns short reads - #4841
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void-ptr974 wants to merge 2 commits into
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Fix directIO reader hang when pread returns short reads#4841void-ptr974 wants to merge 2 commits into
void-ptr974 wants to merge 2 commits into
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Pull request overview
This PR fixes a potential hang in DirectReader when using O_DIRECT reads and pread returns a short read: the reader now advances by the aligned portion actually read (and fails fast if no aligned progress is possible), preventing repeated reads at the same offset. It also tightens buffer-copying to only return bytes that are actually available within the currently loaded block, and adds a regression test for aligned short-read progress.
Changes:
- Fix aligned progress calculation in
DirectReader.readBlock()for shortpreadresults and fail fast on zero aligned progress. - Ensure
readBytesIntoBuf()copies only the bytes available in the current cached block. - Add a unit test that simulates aligned short reads and verifies the reader advances to the next aligned offset.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/storage/directentrylogger/DirectReader.java | Fixes short-read alignment progress and restricts copying to bytes available in the current block. |
| bookkeeper-server/src/test/java/org/apache/bookkeeper/bookie/storage/directentrylogger/TestDirectReader.java | Adds a regression test to ensure aligned short reads advance the read offset and complete. |
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| .kv("requestedBytes", blockSize) | ||
| .kv("offset", blockStart) | ||
| .kv("expectedBytes", Math.min(blockSize, bytesAvailable)) |
| .kv("size", size).toString()); | ||
| } | ||
| return nativeBuffer.readByteBuf(buf, offsetInBuffer, size); | ||
| return nativeBuffer.readByteBuf(buf, offsetInBuffer, sizeInBuffer); |
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DirectReader performs aligned O_DIRECT reads into a reusable native buffer. Short reads must preserve alignment, and failed partial reads must not leave modified buffer contents associated with stale cache metadata.
This change:
Tests:
mvn -pl bookkeeper-server -DskipTests=false -Dtest=TestDirectReader testmvn -pl bookkeeper-server -DskipTests checkstyle:checkgit diff --check