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https://issues.apache.org/jira/browse/ZOOKEEPER-900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12932995#action_12932995
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Vishal K commented on ZOOKEEPER-900:
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Hi Flavio,
Thanks. I will take shutting down of worker threads in a separate
jira.
I am cleaning up QCM further to incorporate the change mentioned in my
comment on 02/Nov/10 02:09 PM.
I have a few more questions:
1. I have a question about the following piece of code in QCM:
if (remoteSid == QuorumPeer.OBSERVER_ID) {
/*
* Choose identifier at random. We need a value to identify
* the connection.
*/
remoteSid = observerCounter--;
LOG.info("Setting arbitrary identifier to observer: " + remoteSid);
}
Should we allow this? The problem with this code is that if a peer
connects twice with QuorumPeer.OBSERVER_ID, we will end up creating
threads for this peer twice. This could result in redundant
SendWorker/RecvWorker threads.
I haven't used observers yet. The documentation
http://hadoop.apache.org/zookeeper/docs/r3.3.0/zookeeperObservers.html
says that just like followers, observers should have server IDs. In
which case, why do we want to provide a wild-card?
2. Should I add a check to reject connections from peers that are not
listed in the configuration file? Currently, we are not doing any
sanity check for server IDs. I think this might fix ZOOKEEPER-851.
The fix is simple. However, I am not sure if anyone in community
is relying on this ability.
-Vishal
> 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: Vishal K
> Priority: Critical
> Fix For: 3.4.0
>
> Attachments: ZOOKEEPER-900.patch, ZOOKEEPER-900.patch1,
> ZOOKEEPER-900.patch2
>
>
> 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
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