Re: [ecf-dev] zookeeper discovery comes and goes

[ahmed.aadel@xxxxxxxxxxxxxxxxxx]

Hi Bryan,

Currenly, this client session timeout
is not configurable but we can easily externalize it  to some system
property or such,  what do you think  Wim?
I personnally would question the benifits
of  widening that session timeout due to the very  nature of
the discovery role. Generally, the sooner a service  (name for instance
r_osgi using this sevice info to locate and proxy services) relying on
information gotten
 from zoodiscovery is notified
of change, the healthier the services' interaction would be.  Of course
this would be of less impact  for test purposes.

To get back to the intial point,  I'd
appreciate having you confirm (as I can't reproduce your situation) this
is a delay issue. That is, the method  org.eclipse.ecf.provider.zookeeper.node.internal.NodeReader.process(WatchedEvent
event) has 
indeed received either KeeperState.Disconnected
or KeeperState.Expired event before
declaring a service is undiscovered.

In waiting the bug fix (if agreed upon)
of extenalizing client session-timeout configuration, you might want to
see the effect forehand  yourself for your own case by changing that
session-timeout value in the source code (org.eclipse.ecf.provider.zookeeper)
and
 using this  changed source
bundle  in your runtime instead. There are 3 methods needing minor
change:
org.eclipse.ecf.provider.zookeeper.node.internal.ReadRoot.connect()
org.eclipse.ecf.provider.zookeeper.node.internal.WriteRoot.connect()
org.eclipse.ecf.provider.zookeeper.node.internal.WriteRoot.initWriteKeeper()

in these methods just change the occuring
3000 value (indicates session interval) in "new ZooKeeper(.., 3000,
..)" to the value you want to test with.

By the way, how come you've experienced
such a delay while running the whole thing on the same machine!

Hope it helped a bit,

kind regards,
ahmed

From:	Bryan Hunt <bhunt@xxxxxxx>
To:	"Eclipse Communication Framework (ECF) developer mailing list." <ecf-dev@xxxxxxxxxxx>
Date:	15-10-2010 16:28
Subject:	Re: [ecf-dev] zookeeper discovery comes and goes

---

Hi Ahmed,

I assume that ECF takes care of sending the heart beats.
 How do I configure the session-timeout interval?

Bryan

On Oct 13, 2010, at 8:08 AM, ahmed.aadel@xxxxxxxxxxxxxxxxxx
wrote:


Hi, 

A service  is signaled as undiscovered either because it is indeed
unpublished from the other end point (nothing new) ,  the connection
is lost or session expired. These are  dealt with in NodeReader.process(WatchedEvent
event),  this is
the closest point to the underlying zookeeper that get informed that a
data node is deleted or no more reachable, so I'd say debug that short
method to see wether it is a genuine serivce undiscovery or one masking
a session/connection loss. The recieved event is intuitive and should be
strighforward. 
 A word about the session  mentioned above:   a  client
should send heart beats within a session-timeout interval (currently set
to 3000) to be considered still alive. 

best regards, 
ahmed

From:	Wim Jongman <wim.jongman@xxxxxxxxx>
To:	"Eclipse Communication Framework (ECF) developer mailing list." <ecf-dev@xxxxxxxxxxx>, ahmed.aadel@xxxxxxxxxxxxxxxxxx
Date:	13-10-2010 11:02
Subject:	Re: [ecf-dev] zookeeper discovery comes and goes

---

Hi Bryan, 

AFAIK the discovery mechanism does not in itself guard the connection and
decides to drop it. It merely listens and propagates service registrations/deregistrations
to the distribution provider. 

I would say this behavior should be seen with other discovery mechanisms
as well. 

Ahmed can you think of reasons why this could happen? 

Regards, 

Wim 

On Tue, Oct 12, 2010 at 4:56 PM, Bryan Hunt <bhunt@xxxxxxx>
wrote: 
I'm seeing a strange problem with zookeeper service discovery.  I've
been experimenting with YourKit and noticed a ConcurrentModificationException
as reported here: https://bugs.eclipse.org/bugs/show_bug.cgi?id=327170

When I went to capture a better stack trace, I noticed that when I remotely
connected with YourKit, the client reported zookeeper undiscovered one
of my 4 remote services.  When I disconnect and reconnect YourKit,
the client reports that zookeeper discovers 4 remote services.

This problem appears repeatable.  The client and all 4 remote services
are running on the same machine.  Each remote service is running in
it's own JVM.  Any ideas on what is going on, or suggestions for tracking
down the problem?  Is there by chance some sort of very short keepalive
that might be having problems if there were a network delay or thread delay
when YourKit connects to the client JVM?

Bryan
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