[
https://issues.apache.org/jira/browse/ZOOKEEPER-900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12928590#action_12928590
]
Vishal K commented on ZOOKEEPER-900:
------------------------------------
Hi Flavio,
Thanks for your feedback. I will do the code changes.
For point 2 above, I was referring to the code that deletes the SenderWorker
and ReceiveWorker pair after receiving a connect request. I was concerned that
a peer might send frequent connect request before to the remote peer before the
remote peer can initiate connection back. But I think the
Notification n = recvqueue.poll(notTimeout, TimeUnit.MILLISECONDS); in
lookForLeader will prevent this scenario. Also, this won't be a concern if we
decide to remove the part that kills the pair for each connect.
I am also thinking of adding a sanity check that will accept connections only
from peers that are not listed in the zoo.cfg file or OBSERVER_ID.
I have not used observes so far. Can you please explain why a node will use
OBSERVER_ID instead of its sid? In particular, I am referring to the following
code in QuorumCnxManager:
// Read server id
sid = Long.valueOf(msgBuffer.getLong());
if(sid == QuorumPeer.OBSERVER_ID){
/*
* Choose identifier at random. We need a value to identify
* the connection.
*/
sid = observerCounter--;
LOG.info("Setting arbitrary identifier to observer: " + sid);
}
> FLE implementation should be improved to use non-blocking sockets
> -----------------------------------------------------------------
>
> Key: ZOOKEEPER-900
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-900
> Project: Zookeeper
> Issue Type: Bug
> Reporter: Vishal K
> Assignee: Flavio Junqueira
> Priority: Critical
>
> From earlier email exchanges:
> 1. Blocking connects and accepts:
> a) The first problem is in manager.toSend(). This invokes connectOne(), which
> does a blocking connect. While testing, I changed the code so that
> connectOne() starts a new thread called AsyncConnct(). AsyncConnect.run()
> does a socketChannel.connect(). After starting AsyncConnect, connectOne
> starts a timer. connectOne continues with normal operations if the connection
> is established before the timer expires, otherwise, when the timer expires it
> interrupts AsyncConnect() thread and returns. In this way, I can have an
> upper bound on the amount of time we need to wait for connect to succeed. Of
> course, this was a quick fix for my testing. Ideally, we should use Selector
> to do non-blocking connects/accepts. I am planning to do that later once we
> at least have a quick fix for the problem and consensus from others for the
> real fix (this problem is big blocker for us). Note that it is OK to do
> blocking IO in SenderWorker and RecvWorker threads since they block IO to the
> respective !
peer.
> b) The blocking IO problem is not just restricted to connectOne(), but also
> in receiveConnection(). The Listener thread calls receiveConnection() for
> each incoming connection request. receiveConnection does blocking IO to get
> peer's info (s.read(msgBuffer)). Worse, it invokes connectOne() back to the
> peer that had sent the connection request. All of this is happening from the
> Listener. In short, if a peer fails after initiating a connection, the
> Listener thread won't be able to accept connections from other peers, because
> it would be stuck in read() or connetOne(). Also the code has an inherent
> cycle. initiateConnection() and receiveConnection() will have to be very
> carefully synchronized otherwise, we could run into deadlocks. This code is
> going to be difficult to maintain/modify.
> Also see: https://issues.apache.org/jira/browse/ZOOKEEPER-822
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
