Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Plain View
Zookeeper >> mail # dev >> zookeeper_interest returning ZOK on Connection Loss


Copy link to this message
-
zookeeper_interest returning ZOK on Connection Loss
I have a fairly simple single-threaded C client set up -- single-threaded
because we are embedding zk in the node.js/libuv runtime -- which consists of
the following algorithm:

zookeeper_interest(); select();
// perform zookeeper api calls
zookeeper_process();

I've noticed that zookeeper_interest in the C client never returns error if it
is unable to connect to the zk server.

From the spec of the zookeeper_interest API, I see that zookeeper_interest is
supposed to return ZCONNECTIONLOSS when disconnected from the client. However,
digging into the code, I see that the client is making a non-blocking connect
call
https://github.com/apache/zookeeper/blob/trunk/src/c/src/zookeeper.c#L1596-1613
,  and returning ZOK
https://github.com/apache/zookeeper/blob/trunk/src/c/src/zookeeper.c#L1684

If we assume that the server is not up, this will mean that the subsequent
select() call would return 0, since the fd is not ready, and future calls to
zookeeper_interest will always return 0 and not the expected ZCONNECTIONLOSS.
Thus an upstream client will never be aware that the connection is lost.

I don't think this is the expected behavior. I have temporarily patched the zk
C client such that zookeeper_interest will return ZCONNECTIONLOSS if it's still
unable to connect after session_timeout has been exceeded.

Is this the right interpretation of the API? Are you guys open to taking the
patch I described?

-Yunong
+
Michi Mutsuzaki 2012-11-05, 18:33
+
Yunong Xiao 2012-11-05, 21:19
+
Michi Mutsuzaki 2012-11-05, 21:59
+
Yunong Xiao 2012-11-05, 22:16
+
Michi Mutsuzaki 2012-11-06, 07:24
+
Yunong Xiao 2012-11-14, 01:08
+
Anthony Barré 2013-03-27, 09:41