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From joshelser <...@git.apache.org>
Subject [GitHub] zookeeper pull request #186: ZOOKEEPER-2711 Avoid synchronization on NettySe...
Date Tue, 07 Mar 2017 22:08:19 GMT
Github user joshelser commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/186#discussion_r104792592
  
    --- Diff: src/java/main/org/apache/zookeeper/server/NettyServerCnxnFactory.java ---
    @@ -162,7 +162,7 @@ public void messageReceived(ChannelHandlerContext ctx, MessageEvent
e)
                                 + " from " + ctx.getChannel());
                     }
                     NettyServerCnxn cnxn = (NettyServerCnxn)ctx.getAttachment();
    -                synchronized(cnxn) {
    +                synchronized(cnxn.getRpcLock()) {
                         processMessage(e, cnxn);
    --- End diff --
    
    > Now one thread can be in processMessage while another thread is getting stats about
the connection. Is that ok?
    
    I believe this is OK. We can receive two concurrent `stat` commands, but we only process
one of them at a time. I'm also not a Netty wizard, so I could be wildly wrong :)
    
    > Basically I am wondering if there is any other code out there that should now sync
on what getRpcLock() returns.
    
    That's a good point. I had looked to see that there were multiple other methods in `ServerCnxn`
which were also synchronized (thus, changing `dumpConnectionInfo(..)` wouldn't have been sufficient).
I didn't look to see if there's another code-path which is also synchronizing on the `NettyServerCnxn`
(or `ServerCnxn`).


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