Re: serviceRemoved / serviceAdded problem

Hi Francisco,

Francisco Mourao wrote:
> And do you think lease renewal can be related to the serviceRemoved /
> serviceAdded problem? If services are apparently ok, could it be the cpu
> load to generate renewal failure?
>

I have certainly seen cases where this sort of thing can happen - can be
caused by a bunch of different things:

(1)     Network congestion/load

(2)     Load on the client machine

(3)     Load on the server machine

> Is there anything else that could cause this serviceRemoved / serviceAdded
> events?
>

Nothing that immediately springs to mind but of course, my mind is old
and leaky :)

Best,

Dan.


> Thanks again
>
>
> On Tue, 16 Jan 2007 20:33:09 +0000, Dan Creswell <[email protected]>
> wrote:
>
>> Francisco Dário Mourão wrote:
>>> Hi all again,
>>>
>>>
>>>
>>> I have an application running a number x of Jini services (according to
>>> configuration x can be over than 10 in a specific production
> environment).
>>> For now all the services run in a single machine (RedHat9.0 jsdk5).
>>>
>>> I’m using Jini 2.1.
>>>
>>> I use the http server provided in classserver.jar. I also use reggie,
>>> norm, and fiddler services.
>>>
>>>
>>>
>>> Some services act as client of other services.
>>>
>>> Each service acting as a client, has a lookup cache to the services it
>>> uses more frequently:
>>>
>>>             …
>>>
>>> discover = new LookupDiscoveryManager(groups, locators, null);
>>>
>>>       sdm = new ServiceDiscoveryManager(discover, new
>>> LeaseRenewalManager(), conf);
>>>
>>>
>>>
>>>       serviceTemplate = new ServiceTemplate (null,
>>>
>>>                                              new Class[]
> {IServiceX.class},
>>>                                              new Entry[] {entry});
>>>
>>>
>>>
>>> lCache = sdm.createLookupCache(serviceTemplate, null, new
>>> ServiceListener());
>>>
>>> …
>>>
>>> In this case a service say ClientService uses a lookupCache for the
>>> service x (IServiceX).
>>>
>>>
>>>
>>> The application runs with no problem for while. Sometimes it takes 5 or
>>> more days until the problem occurs…
>>>
>>>
>>>
>>> THE PROBLEM:
>>>
>>>
>>>
>>> At a given point in time, I don’t know why, the client services
> receive
>>> through their implementation of ServiceListener(), the notifications of
>>>
>>> serviceRemoved and then serviceAdded for all the services it is a client
>>> (all the services in the LookupCache).
>>>
>>>
>>>
>>> The application recovers a few minutes later because there is a
>>> corresponding serviceAdded  few moments after a serviceRemoved
>>> notification is sent,
>>>
>>> but until it recovers the application doesn’t respond which is
> expected
>>> according to what’s happening.
>>>
>>> *Note*: with Jini 2.0_2 I had the same problem, but sometimes some
>>> client services only received a serviceRemoved notification and no
>>> corresponding serviceAdded. That would crash my application.
>>>
>>> Changing to Jini 2.1 corrected the problem of not receiving the
>>> corresponding serviceAdded… but the question remains:
>>>
>>>
>>>
>>> QUESTION:
>>>
>>> What causes this serviceRemoved / serviceAdded sequence?
>>>
>>>
>>>
>>> Could be service lease expiration?
>>>
>>> I’m trying get a cpu analyser to see if the cpu has some peeks. Could
>>> this be associated? I wonder if in a peek of cpu it can’t renew
> services
>>> (???)
>>>
>>>
>>>
>>> But I’m a little bit confused because
>>> net.jini.lookup.ServiceDiscoveryManager.registerListener() does this:
>>>
>>>
>>>
>>> leaseRenewalMgr.renewFor(eventLease,
>>>
>>>                          duration, //equals to LONG.MAX_VALUE
>>>
>>>                          new LeaseListenerImpl(proxy));
>>>
>>>
>>>
>>> and according to api doc this is the same as
>>>
>>>
>>>
>>> renewFor(eventLease, duration, Lease.FOREVER, new LeaseListenerImpl
> (proxy));
>>>
>>>
>>> so this means that the lease will last LONG.MAX_VALUE and will never
> need to be renewed (because renewal duration = Lease.FOREVER) right?
>> Wrong I think - you can ask for a lease that long but you aren't
>> guarenteed to get it.
>>
>> In this case, I imagine you'll be granted a 5 minute lease or so which
>> thus must be renewed relatively frequently.
>>
>> Your services using JoinManager to register with lookup services will
>> also be doing something similar I suspect.
>>
>> Hope that helps,
>>
>> Dan.
>>
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