reddycharan commented on a change in pull request #1228: Issue #570: Move logic
of unpersistedbytes to bufferedchannel
URL: https://github.com/apache/bookkeeper/pull/1228#discussion_r172317243
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File path:
bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/BufferedChannel.java
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@@ -138,6 +182,20 @@ public long forceWrite(boolean forceMetadata) throws
IOException {
// the force write, any flush that happens after this may or may
// not be flushed
long positionForceWrite = writeBufferStartPosition.get();
+ /*
+ * since forceWrite method is not called in synchronized block, to make
+ * sure we are not undercounting unpersistedBytes, setting
+ * unpersistedBytes to the current number of bytes in writeBuffer.
+ *
+ * since we are calling fileChannel.force, bytes which are written to
+ * filechannel (system filecache) will be persisted to the disk. So we
+ * dont need to consider those bytes for setting value to
+ * unpersistedBytes.
+ *
+ */
+ synchronized (this) {
+ unpersistedBytes.set(writeBuffer.readableBytes());
Review comment:
in flushInternal call, "fileChannel.write(toWrite);" method is called. It
just writes to the file buffer but it is not guaranteed to be persisted to the
storage device, hence flushInternal shouldn't affect unpersistedBytes count in
anyway. But where as in the forceWrite method we are calling fileChannel.force
method which "forces any updates to this channel's file to be written to the
storage device that contains it", hence here we should decrement the count of
the bytes which are written to filechannel.
in summary, way i see this is like following : unpersistedbytes =
writeBuffer.readableBytes + bytes written to filchannel (which are not
persisted yet by calling filechannel.force)
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