Singleton object is still create multiple instances

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AY - 17 Dec 2004 22:20 GMT

I am trying to use .NET remoting technique to implement a cache type of
object, ie, multiple clients access this cache object which has the client
specific information stored. My server config file is like this:

<configuration>
<system.runtime.remoting>
<application>
<service>
<wellknown mode="Singleton" type="MyConns, HFCache"
objectUri="HFCache.MyConns" />
</service>
<channels>
<channel port="8001" ref="tcp" />
</channels>
<lifetime leaseTime="10M" renewOnCallTime="5M" />
</application>
</system.runtime.remoting>
</configuration>

Client side config file:

<configuration>
<system.runtime.remoting>
<application>
<client>
<wellKnown type="MyConns, HFCache"
url="tcp://localhost:8001/HFCache.MyConns" />
</client>
<channels>
<channel ref="tcp" />
</channels>
</application>
</system.runtime.remoting>
</configuration>

In the client code:

MyConns conn = new MyConns();

The a new instance of MyConns is created. (In my MyConns constructor, I
write to EventLog, I saw there more than one entries in EventLog, saying the
MyConns object is created)

I couldn't see where it might went wrong. Please help, really appreciate,
Thank you,

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todd.mancini@gmail.com - 17 Dec 2004 22:31 GMT

Do you have more than one instance of MyConns at the same time? A
Singleton just ensures that there will only be one instance at any
given time, but it is possible for the instance to expire, and then,
when needed, a new singleton instance to be created. So, even with
Singletons, unless you control the lease to never expire, the
constructor CAN be called more than once if an instance expires.

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Ken Kolda - 17 Dec 2004 22:57 GMT

My guess is that you're not actually instantiating the object on the
server -- you're creating local instances. I see that you have the word
"wellKnown" miscapitalized in your client's config file, so that may be the
first issue (assuming it's accurately transcribed).

To verify you're getting a remote object instead of a local instance, call
RemotingServices.IsTransparentProxy() on the instance of your remote object,
e.g.

MyConn conn = new MyConn();
Debug.Assert(RemotingServices.IsTransparentProxy(conn));

If the assertion fails, you've created a local instance, which explains why
you're getting multiple instance created.

As second possibility (although I doubt this based on your description) is
that the lifetime of the remote object is expiring. If your two method calls
are separated by more than 5 minutes, the object may have been disconnected
and a new instance would be created to service requests. If you want to
ensure on a single MyConn instance is created, be sure to return null from
InitializeLifetimeService().

Ken

> I am trying to use .NET remoting technique to implement a cache type of
> object, ie, multiple clients access this cache object which has the client
[quoted text clipped - 41 lines]
> I couldn't see where it might went wrong. Please help, really appreciate,
> Thank you,

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Singleton object is still create multiple instances

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