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HDDS-6157. More consistent synchronization in InputStreams #2965

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merged 1 commit into from Jan 12, 2022
Merged

HDDS-6157. More consistent synchronization in InputStreams #2965

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2 changes: 1 addition & 1 deletion hadoop-hdds/client/src/main/java/org/apache/hadoop/hdds/scm/storage/BlockInputStream.java
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Expand Up @@ -512,7 +512,7 @@ synchronized long getBlockPosition() {
}

@Override
public void unbuffer() {
public synchronized void unbuffer() {
storePosition();
releaseClient();

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8 changes: 4 additions & 4 deletions hadoop-ozone/client/src/main/java/org/apache/hadoop/ozone/client/io/KeyInputStream.java
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Expand Up @@ -351,14 +351,14 @@ public boolean seekToNewSource(long targetPos) throws IOException {
}

@Override
public int available() throws IOException {
public synchronized int available() throws IOException {
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This seems to return remaining value, if multiple people are operating on this stream, with synchronised also this can give stale values.
Just out of curiosity: Any pointers in which use case having this synchronised will help

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BTW, available() in S3AInputStream and HDFS's DFSInputStream are both synchronized.

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if multiple people are operating on this stream, with synchronised also this can give stale values

Correct, that may be a design choice of InputStream in general.

However, synchronization helps not only with concurrent usage, but also sequential usage in multiple threads, as it provides visibility guarantees.

I don't have a use case for making this specific method synchronized, but nor do I for the other methods that are already synced. It's just a matter of consistency.

checkOpen();
long remaining = length - getPos();
return remaining <= Integer.MAX_VALUE ? (int) remaining : Integer.MAX_VALUE;
}

@Override
public void close() throws IOException {
public synchronized void close() throws IOException {
closed = true;
for (BlockInputStream blockStream : blockStreams) {
blockStream.close();
Expand Down Expand Up @@ -388,7 +388,7 @@ public long getRemainingOfIndex(int index) throws IOException {
}

@Override
public long skip(long n) throws IOException {
public synchronized long skip(long n) throws IOException {
if (n <= 0) {
return 0;
}
Expand All @@ -399,7 +399,7 @@ public long skip(long n) throws IOException {
}

@Override
public void unbuffer() {
public synchronized void unbuffer() {
for (BlockInputStream is : blockStreams) {
is.unbuffer();
}
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