HDDS-15930. Avoid zero-length chunk in TestContainerOperations

[henrybear327]

What changes were proposed in this pull request?

This PR fixes the flake, which is the TestContainerOperations#testContainerStateMachineIdempotency, by ensuring that its randomly generated chunk is non-empty.

Root cause investigation

Taken from the CI run log.

The failing CI run showed that the test generated a zero-byte chunk:

2026-07-20 21:42:37,572 [ForkJoinPool-1-worker-1] DEBUG scm.XceiverClientGrpc (XceiverClientGrpc.java:sendCommandWithRetry(495)) - Executing command cmdType: WriteChunk traceID: "" containerID: 67 datanodeUuid: "8a3fc17b-fb86-4d79-9be3-3d51133d4f50" writeChunk { blockID { containerID: 67 localID: 116954481136238947 blockCommitSequenceId: 0 } chunkData { chunkName: "116954481136238947.data.0" offset: 0 len: 0 } data: "<redacted>" } version: 3 on datanode 8a3fc17b-fb86-4d79-9be3-3d51133d4f50(localhost/127.0.0.1)

The following PutBlock also described an empty block:

2026-07-20 21:42:37,578 [ForkJoinPool-1-worker-1] DEBUG scm.XceiverClientGrpc (XceiverClientGrpc.java:sendCommandWithRetry(495)) - Executing command cmdType: PutBlock traceID: "" containerID: 67 datanodeUuid: "8a3fc17b-fb86-4d79-9be3-3d51133d4f50" putBlock { blockData { blockID { containerID: 67 localID: 116954481136238947 blockCommitSequenceId: 0 } chunks { chunkName: "116954481136238947.data.0" offset: 0 len: 0 } size: 0 } } version: 3 on datanode 8a3fc17b-fb86-4d79-9be3-3d51133d4f50(localhost/127.0.0.1)

This led to the following failure sequence:

2026-07-20 21:42:37,580 [8a3fc17b-fb86-4d79-9be3-3d51133d4f50-ChunkReader-2] WARN  keyvalue.KeyValueHandler (ContainerUtils.java:logAndReturnError(99)) - Operation: PutBlock , Trace ID:  , Message: Chunk file not found: /home/runner/work/ozone/ozone/hadoop-ozone/integration-test/target/test-dir/MiniOzoneClusterImpl-3f677bbb-a268-48d5-a8e5-e030d249b108/ozone-metadata/datanode-5/data-0/hdds/3f677bbb-a268-48d5-a8e5-e030d249b108/current/containerDir0/67/chunks/116954481136238947.block , Result: UNABLE_TO_FIND_CHUNK , StorageContainerException Occurred.

then

Marked container UNHEALTHY from OPEN

then

Operation: CloseContainer
Message: Cannot close container #67 while in UNHEALTHY state.
Result: CONTAINER_UNHEALTHY

By tracing the code, we can confirm why the chunk file was missing, because FilePerBlockStrategy intentionally skips empty chunk writes (this log was taken from a local reproduction run since this DEBUG log isn't showing up in the CI run log)

2026-07-22 01:08:45,148 [e5111eb4-3873-4f6a-868f-2f14e06a9e36-ChunkReader-6] DEBUG impl.FilePerBlockStrategy (FilePerBlockStrategy.java:writeChunk(134)) - Skip writing empty chunk ChunkInfo{chunkName='116960482106540033.data.0, offset=0, len=0} in stage COMBINED

Therefore, when the test randomly selected zero, WriteChunk created no file, PutBlock failed to find it, and the datanode marked the container unhealthy. The final CloseContainer exception was a downstream symptom.

Proposed fix

The test previously generated a length in the range [0, 1024), just make it non-empty [1, 1024), would work.

As the test is intended to verify container state-machine idempotency, not empty-chunk behavior, so excluding zero keeps its randomized input within the valid scenario being tested.

What is the link to the Apache JIRA

[Please create an issue in ASF JIRA before opening a pull request, and you need to set the title of the pull
request which starts with the corresponding JIRA issue number. (e.g. HDDS-XXXX. Fix a typo in YYY.)

If you do not have an ASF Jira account yet, please follow the first-time contributor
instructions in the Jira guideline.

(Please replace this section with the link to the Apache JIRA)](https://issues.apache.org/jira/browse/HDDS-15930)

How was this patch tested?

https://github.com/apache/ozone/actions/runs/29876934271

https://github.com/henrybear327/ozone/actions/runs/29906444081

[anuragp010]

With Chunk length = 0, same error is reproduced.
[ERROR] Tests run: 10, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.216 s <<< FAILURE! -- in org.apache.ozone.test.NonHATests$ContainerOperations [ERROR] org.apache.ozone.test.NonHATests$ContainerOperations.testContainerStateMachineIdempotency -- Time elapsed: 0.048 s <<< ERROR! org.apache.hadoop.hdds.scm.container.common.helpers.StorageContainerException: Cannot close container #70 while in UNHEALTHY state.

[henrybear327]

@chungen0126 I have attempted to enable the flaky-test-check workflow https://github.com/henrybear327/ozone/actions/runs/29906444081. Not sure if this is what you would like to get run :)

Thanks

[chungen0126]

+1 LGTM. I'll merge after ci pass

[sarvekshayr]

@henrybear327 Looks like the flaky-test-check(https://github.com/henrybear327/ozone/actions/runs/29906444081) did not run the test at all.

Please trigger another one with the right configs before we merge this.