WCF - have client check for service availability [duplicate]

Question

I have a client-server system, both sides written by me, and I would like to put the clients in an 'offline' state when the server disconnects/dies, and then automatically bring them back 'online' when the server is available again.

For the first part, I listen for channel faulted events and handle that by setting the client to offline. I then start calling a 'ping' service on the server (every 30 sec.) which just returns a bool if it is alive. Once it is alive the client gets the bool and switches back online.

This all works, the problem I am having is that when the client calls the ping service and the server is down, no response is sent (obviously) and eventually, after about 2mins I get an endpoint not found exception. By this time I have already tried 3-4 more pings and hence have 3-4 exceptions brewing.

My question is, how can I deal with the ping service more gracefully? Ideally I would like to periodically call a service that lets me know if it is online, and instantly lets me know if it is not.

Cadmus

did you tried it? any sample code? Maybe ServiceContract with Ping method and test availability for database connection, active directory, FileSystem, Email, Ftp, SFtp, SMS API, etc – Leakey

Answer 1

What about this:

• if you detect a server disconnect, enter a "Ping" mode
• in the "ping mode", you set the client's "sendTimeout" to something very short, e.g. something like 2 secs or so, since your call to the service's Ping method should be answered almost immediately
• once your "Ping" worked successfully, you again re-create the client proxy and set the client's "sendTimeout" back to the original value (default is 1 minute - depends on what makes sense for you, 15 seconds, 30 seconds - whatever)

That way, if you're in "Ping mode", you get your responses (or timeouts) quickly and you can detect the availability of the service quickly.

Sirrah

Thanks Marc, great idea this is what I have done. I had completely forgotten that one can edit binding timeouts on the fly like this. – Cadmus

How to detect server is disconnected? – Landlocked

@Ashutosh: if the server is disconnected, your call will fail with one of several possible errors ("not found" or "timeout" or othesr) – Sirrah

sample code about 1) How to detect server is disconnected? 2) re-create the client proxy 3) set the client's "sendTimeout" – Leakey