[Backport Fix to staging-2.2.x]: Prevent Hadoop directory copy failures by correctly setting generation id Preconditions #1466
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dheerajsngh
commented
Aug 25, 2025
dheerajsngh
commented
- Origin PR/
…ration ID preconditions (#1363)
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/gcbrun |
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Summary of Changes
Hello @dheerajsngh, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
This pull request backports a critical fix aimed at preventing Hadoop directory copy failures. It addresses an underlying issue where Google Cloud Storage (GCS) read operations were incorrectly applying generation match preconditions when the generation ID was zero. The changes ensure that GCS read channels only utilize positive generation IDs for preconditions, thereby stabilizing and improving the reliability of copy operations.
Highlights
- Generation ID Precondition Fix: Modified 'GoogleCloudStorageClientReadChannel.java' and 'GoogleCloudStorageReadChannel.java' to ensure that generation match preconditions are only applied when the generation ID is greater than zero. This prevents issues when a generation ID of 0 is encountered.
- Test Cases for Generation ID Handling: Added new unit tests in 'GoogleCloudStorageClientReadChannelTest.java' and 'GoogleCloudStorageReadChannelTest.java' to verify the correct behavior of generation ID handling. These tests specifically check that positive generation IDs are used as preconditions, while zero generation IDs are not.
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Code Review
This pull request backports a fix to prevent Hadoop directory copy failures. The fix involves adding a check to ensure that a generation ID is positive before using it as a precondition in GCS read operations. This prevents issues where a generation ID of 0 was being incorrectly used. The changes are applied consistently across GoogleCloudStorageClientReadChannel and GoogleCloudStorageReadChannel, and new tests have been added to verify the corrected behavior. My review includes suggestions to improve maintainability by reducing code duplication in both the application and test code.
| storageRequestFactory.objectsGetData( | ||
| resourceId.getBucketName(), resourceId.getObjectName()); | ||
| if (resourceId.hasGenerationId()) { | ||
| if (resourceId.hasGenerationId() && resourceId.getGenerationId() > 0) { |
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This condition resourceId.hasGenerationId() && resourceId.getGenerationId() > 0 is also used in initMetadata (line 778) and createMetadataRequest (line 1152). To improve maintainability and reduce duplication, consider extracting this logic into a private helper method, for example shouldUseGenerationId().
| @Test | ||
| public void read_withZeroGeneration_doesNotUseGenerationMatchPrecondition() throws IOException { | ||
| long generation = 0L; | ||
| GoogleCloudStorageItemInfo itemInfo = | ||
| GoogleCloudStorageItemInfo.createObject( | ||
| new StorageResourceId(V1_BUCKET_NAME, OBJECT_NAME, generation), | ||
| /* creationTime= */ 10L, | ||
| /* modificationTime= */ 15L, | ||
| /* size= */ OBJECT_SIZE, | ||
| /* contentType= */ "text/plain", | ||
| /* contentEncoding= */ "text", | ||
| /* metadata= */ null, | ||
| /* contentGeneration= */ generation, | ||
| /* metaGeneration= */ 2L, | ||
| /* verificationAttributes= */ null); | ||
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| readChannel = getJavaStorageChannel(itemInfo, DEFAULT_READ_OPTION); | ||
| readChannel.read(ByteBuffer.allocate(1)); | ||
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| ArgumentCaptor<BlobSourceOption> optionsCaptor = | ||
| ArgumentCaptor.forClass(BlobSourceOption.class); | ||
| verify(mockedStorage).reader(any(BlobId.class), optionsCaptor.capture()); | ||
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| assertThat(optionsCaptor.getAllValues()) | ||
| .doesNotContain(BlobSourceOption.generationMatch(generation)); | ||
| } |
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The test read_withZeroGeneration_doesNotUseGenerationMatchPrecondition is very similar to read_withPositiveGeneration_usesGenerationMatchPrecondition. To improve readability and maintainability, you could refactor them into a single helper method that is called by two separate tests, or use a parameterized test. The helper method could take the generation and a boolean indicating whether the precondition should be present as parameters.
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