ISSUE-19808: [Bug] org.apache.bookkeeper.mledger.impl.OpFindNewest#readEntryComplete

[sijie]

Original Issue: apache#19808

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Version

2.11
org.apache.bookkeeper.mledger.impl.OpFindNewest#readEntryComplete

Minimal reproduce step

1.state = checkFirst, condition.apply(entry) = true
The following code is executed:

lastMatchedPosition = position;
                // check last entry
                state = State.checkLast;
                PositionImpl lastPosition = ledger.getLastPosition();
                searchPosition = ledger.getPositionAfterN(searchPosition, max, PositionBound.startExcluded);
                if (lastPosition.compareTo(searchPosition) < 0) {
                    if (log.isDebugEnabled()) {
                        log.debug("first position {} matches, last should be {}, but moving to lastPos {}", position,
                                searchPosition, lastPosition);
                    }
                    searchPosition = lastPosition;
                }
                find();

crux of the problem：
The calculated searchPosition may be equal to the current entry position, then, after calling find(), state=checkLast is executed the next time, this causes condition.apply(entry) to be called twice, and with the same entry.

What did you expect to see?

I'd like to add a check code, for example:

if (position.equals(searchPosition)) {
                    callback.findEntryComplete(position, OpFindNewest.this.ctx);
                    return;
                }

        case checkFirst:
            if (!condition.apply(entry)) {
                // If no entry is found that matches the condition, it is expected to pass null to the callback.
                // Otherwise, a message before the expiration date will be deleted due to message TTL.
                // cf. https://github.com/apache/pulsar/issues/5579
                callback.findEntryComplete(null, OpFindNewest.this.ctx);
                return;
            } else {
                lastMatchedPosition = position;
                // check last entry
                state = State.checkLast;
                PositionImpl lastPosition = ledger.getLastPosition();
                searchPosition = ledger.getPositionAfterN(searchPosition, max, PositionBound.startExcluded);
                if (position.equals(searchPosition)) {
                    callback.findEntryComplete(position, OpFindNewest.this.ctx);
                    return;
                }
                if (lastPosition.compareTo(searchPosition) < 0) {
                    if (log.isDebugEnabled()) {
                        log.debug("first position {} matches, last should be {}, but moving to lastPos {}", position,
                                searchPosition, lastPosition);
                    }
                    searchPosition = lastPosition;
                }
                find();
            }
            break;

What did you see instead?

condition.apply(entry) is executed twice

Anything else?

no

Are you willing to submit a PR?

• I'm willing to submit a PR!