[ZOOKEEPER-59] Synchronized block in NIOServerCnxn

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.0
• Component/s: server
• Hadoop Flags: Reviewed
• Release Note: not a blocker for 3.2, moving to 3.3
• Assignee: Flavio Paiva Junqueira
• Reporter: Flavio Paiva Junqueira
• Created: 30/Jun/08 11:20
• Updated: 26/Mar/10 17:24
• Resolved: 09/Mar/10 02:01

Description

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:

NIOServerCnxn.readRequest@444
...
          synchronized (this) {
                outstandingRequests++;
                // check throttling
                if (zk.getInProcess() > factory.outstandingLimit) {
                    disableRecv();
                    // following lines should not be needed since we are already
                    // reading
                    // } else {
                    // enableRecv();
                }
            } 

NIOServerCnxn.sendResponse@740
...
         synchronized (this.factory) {
                outstandingRequests--;
                // check throttling
                if (zk.getInProcess() < factory.outstandingLimit
                        || outstandingRequests < 1) {
                    sk.selector().wakeup();
                    enableRecv();
                }
            }

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.