Greg, Your answer is what I wanted to know. Thank you. Shinji Matsumoto SIOS technology, Inc. On Wed, Mar 26, 2014 at 12:56 AM, Gregory Farnum <greg@xxxxxxxxxxx> wrote: > On Tue, Mar 25, 2014 at 5:50 AM, Shinji Matsumoto > <shinji.matsumoto@xxxxxxxxxxx> wrote: >> Hello all, >> >> I have a question about Ceph notification mechanism. >> http://ceph.com/docs/master/architecture/#object-watch-notify >> >> Scenario: >> >> (1) 3 clients (client1, client2, client3) have interests on a Ceph >> object (object A). Each client calls rados_watch() to register >> notification callback on the object.. >> >> (2) Client1 calls rados_notify() on object A. On client1 and client2, >> the notification is delivered and processed successfully within a >> timeout period. >> >> (3) However on client3, the notification is delivered, but it doesn't >> complete within a timeout period for a temporary reason, such as >> temporarily busy process for instance. >> >> (4) On client1, rados_notify() returns a status of timeout. >> >> (5) On client3, the temporary reason goes away and the notification is >> processed. >> >> (6) Then, client3 attempts to read from object A by a call to rados_read(). >> >> Question: >> >> Will the call to rados_read() attempted at step (6) always succeed, >> always fail or is the behavior unpredictable, which is, it's affected >> by the factors that are not defined in this scenario? > > The success of the read is not impacted by the notify timeout -- you > can order reads using watch-notify, but issues in the watch-notify > framework won't impact reads. Watch-notify is a voluntary thing. IIRC > the OSD involved might kill client3's connection, but it'll just > establish a new one transparently. > -Greg > Software Engineer #42 @ http://inktank.com | http://ceph.com -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
