[CELEBORN-1760][FOLLOWUP] Remove redundant release on data added in flushBuffer

[littlexyw]

What changes were proposed in this pull request?

backport #3224 to branch-0.5
Remove the redundant release of data after OutOfDirectMemoryError appears in flushBuffer.addComponent

Why are the changes needed?

he reason why OutOfDirectMemoryError will appear in flushBuffer.addComponent is that after adding a new component, CompositeByteBuf will determine whether the number of components exceeds the maximum limit. If it exceeds, the existing components will be merged into a large component. At this time, new off-heap memory will be requested. If there is insufficient memory at this time, OutOfDirectMemoryError will be reported, but the new component has been added to flushBuffer at this time. Releasing the new component at this time will cause refcnt error.
Don't worry about the component here not being released causing memory leaks, because it will be released normally in returnBuffer (flush or file destroy or file close).
If writeLocalData does not catch OutOfDirectMemoryError, the impact is as follows:

In the case of a single copy, if #3049 pr is not merged, commitfile will be blocked in waitPendingWrites and fail, because writeLocalData does not correctly decrementPendingWrites. However, this will not cause flushBuffer to exist in memory for a long time, because when shuffle expires, the file will be destroyed, flushBuffer will be returned, and this part of memory will be released.
In the case of dual replicas, in addition to the above problems, the thread of the Eventloop to which replicate-client belongs will be blocked at Await.result(writePromise.future, Duration.Inf) because writePromise is not closed correctly. As a result, this thread will not process other PushData data written by worker-data-replicator to the channels of the Eventloop to which replicate-client belongs. This part of data accumulates in the taskQueue of EventLoop and cannot be canceled, which is the cause of memory leak.

Therefore, if the memory leak occurs after OutOfDirectMemoryError occurs in flushBuffer.addComponent, you only need to catch OutOfDirectMemoryError in writeLocalData, and there is no need to release data after addComponent.

I simulated the scenario where addCompoent had an OutOfDirectMemoryError, and released data after the OutOfDirectMemoryError occurred, and a refcnt error occurred.
oom_fix_error_release.log

At the same time, I simulated the scenario where addCompoent had an OutOfDirectMemoryError and did not release data after the OutOfDirectMemoryError occurred. No refcnt error occurred, commitfiles succeeded, the spark task succeeded, and after commitfiles, the worker diskbuffercount became 0.
celeborn_1760_followup_worker.log

Does this PR introduce any user-facing change?

No.

How was this patch tested?

manual test.

[RexXiong]

LGTM, cc @FMX

[FMX]

LGTM. Thanks. Merged into branch-0.5.