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https://issues.apache.org/jira/browse/ZOOKEEPER-59?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12609250#action_12609250
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Benjamin Reed commented on ZOOKEEPER-59:
----------------------------------------
There are actually two things to guard here: the outstandingBuffers and the
selector loop.
In read request, we really just need:
synchronized (this) {
outstandingRequests++;
}
In sendResponse we need to synchronize on this for outstandingRequests and on
factory for the selector:
synchronized (this) {
outstandingRequests--;
}
synchronized (this.factory) {
// check throttling
if (zk.getInProcess() < factory.outstandingLimit
|| outstandingRequests < 1) {
sk.selector().wakeup();
enableRecv();
}
}
I don't think the synchronize block is needed in doIO. The SectionKey methods
are supposed to be thread safe.
I think you might have found something! If the outstandingRequests count gets
messed up, bad things will happen including the server becoming unresponsive to
a client.
> Synchronized block in NIOServerCnxn
> -----------------------------------
>
> Key: ZOOKEEPER-59
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-59
> Project: Zookeeper
> Issue Type: Bug
> Components: server
> Reporter: Flavio Paiva Junqueira
>
> There are two synchronized blocks locking on different objects, and to me
> they should be guarded by the same object. Here are the parts of the code I'm
> talking about:
> {noformat}
> [EMAIL PROTECTED]
> ...
> synchronized (this) {
> outstandingRequests++;
> // check throttling
> if (zk.getInProcess() > factory.outstandingLimit) {
> disableRecv();
> // following lines should not be needed since we are
> already
> // reading
> // } else {
> // enableRecv();
> }
> }
> {noformat}
> {noformat}
> [EMAIL PROTECTED]
> ...
> synchronized (this.factory) {
> outstandingRequests--;
> // check throttling
> if (zk.getInProcess() < factory.outstandingLimit
> || outstandingRequests < 1) {
> sk.selector().wakeup();
> enableRecv();
> }
> }
> {noformat}
> I think the second one is correct, and the first synchronized block should be
> guarded by "this.factory".
> This could be related to issue ZOOKEEPER-57, but I have no concrete
> indication that this is the case so far.
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