sodonnel commented on code in PR #10415:
URL: https://github.com/apache/ozone/pull/10415#discussion_r3375076536
##########
hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/StreamBlockInputStream.java:
##########
@@ -208,12 +214,40 @@ public synchronized void seek(long pos) throws
IOException {
if (pos == position) {
return;
}
- LOG.debug("{}: seek {} -> {}", this, position, pos);
- closeStream();
+ LOG.debug("{}: seek {} -> {}", getName(streamingReader), position, pos);
+ readBuffer = reuseReadBuffer(readBuffer, pos);
Review Comment:
Lets say we have 32MB pre-read in the queue and we are within the first 1MB.
Then we seek to 10MB offset. `reuseReadBuffer` will return null.
Then later in `read()` we call `dataAvailableToRead` which triggers a call
`streamingReader.read()` if there is no remaining in the buffer or the buffer
is null.
```
private synchronized boolean dataAvailableToRead(int length, boolean
preRead) throws IOException {
if (position >= blockLength) {
return false;
}
initialize();
if (!hasRemaining(readBuffer)) {
readBuffer = streamingReader.read(length, preRead);
}
Preconditions.assertTrue(hasRemaining(readBuffer));
return true;
}
```
Inside streamingReadder.read:
```
private ReadBuffer read(int length, boolean preRead) throws IOException {
checkError();
if (future.isDone()) {
return null; // Stream ended
}
readBlock(length, preRead); // !! Reads more data before polling
while (true) {
final ReadBlockResponseProto proto = poll();
```
It pre-reads more data duplicating data already on the queue and also
pulling more data onto the queue that the pre-read limit.
This is the sort of thing the boundary tests for 'reading within the
pre-read doesn't issue new read calls' would catch.
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