sodonnel commented on code in PR #10415:
URL: https://github.com/apache/ozone/pull/10415#discussion_r3375166979
##########
hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/StreamBlockInputStream.java:
##########
@@ -444,36 +507,16 @@ private ByteBuffer read(int length, boolean preRead)
throws IOException {
readBlock(length, preRead);
while (true) {
- final ByteBuffer buf = readFromQueue();
- if (buf != null && buf.hasRemaining()) {
- return buf;
+ final ReadBlockResponseProto proto = poll();
Review Comment:
Claude suggests there is a problem if we have pre-read to the end of the
stream so the stream is done, and then seek backwards. This is what it says,
although I am not sure how the stream can be done and we are still reading, but
it sounds plausible:
```
"Infinite spin in the read() while-loop when a backward seek leaves stale
ahead-of-position responses in the queue and then the stream ends."
Client at position 50 MB seeks backward to 10 MB; reuseReadBuffer returns
null; streamingReader is alive with ~30 stale responses (for offsets 51–80 MB)
queued. After readBlock() sends a new request at 10
MB, poll() returns each stale response in turn. For each,
getByteBuffer(staleProto, 10 MB) finds blockOffset(10 MB) < protoOffset(51+ MB)
and returns null; read is null; hasRemaining is false; the loop continues. If
the future
completes (stream done) before new responses arrive — e.g. server finishes
sending to the old read boundary — poll() returns null at line 474-475. Line
511 NPEs. The loop has no exit path for a null proto, so even without the NPE
it would spin forever: there is no break or return null when proto is null
and the stream is done."
```
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