I have a simple webbapp deployed in tomcat8. But some HTTP requests requires access to DB with slow queries. Sometimes HTTP client made reset connection. In the same time i'd like to handle it in my webapp for cancel slow query (which result is no longer interesting).
The main question: "How to catch reset connection from client side in phase awaiting response from server". Is it possible? Interrupting thread - the best way for it because I can easly handle it.
When connection is broken from client side tomcat does not interrupts http-nio-X thread. Why? How to do it?
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I start a Client to connect remote Server.
It involves a lot of computation.
Then the Client accidental disconnected.
However the Client's computation is still running on remote Server.
has a way to close it?
It will eventually happen when socket timeout is reached, I guess.
On this previous question: Tell when wcf client lost connection One of the commenters states:
Your service should not care whether a network cable was disconnected.
One feature of TCP is that unless someone is actively sending data, it
can tolerate momentary interruptions in network connectivity.
This is even more true in WCF, where there are layers of extra
framework to help protect you against network unreliability.
I'm having an issue where this is not working correctly. I have WCF client that makes a connection to the server using a DuplexChannelFactory. The connection stays open for 3 minutes. I disconnect the client from the internet and reconnect. The client regains internet connection, however any calls made from the server to that client fail. Once the client reconnects it begins working again.
When I pull the plug on the internet, the client throws several exceptions but the channel is still listed as being in an open state. Once the connection is regained and I made a request from the server to the client, I get errors such as: The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it has been Aborted.
Obviously if the request comes in when the client is offline it won't work, but I'm trying to get it so this channel will recover once the internet comes back without having to set up a new connection.
Should this be working as-is, based on the comment I listed above? Or is there something I need to change to make that actually work?
The issue here is that the channel you're trying to use is in a faulted state, and cannot be used any longer (as the error message indicates).
Your client needs to trap (catch) that exception, and then abort the current channel and create a new one. WCF will not do that for you automatically, you have to code for it yourself.
You could also check the CommunicationState of the channel to see if it is faulted, and recover that way.
A final option would be to use the OnFaulted event handler, and when the channel is faulted, abort the channel and create a new one.
Imagine situation (this is real situation):
There is a WCF client application on laptop.
Laptop is connected by WiFi to internet.
User is doing some stuff (request reply operations) on his laptop at work connected to WCF service.
Then user's laptop is sleep-down and user go home. At home user wake-up his laptop, connect HSPDA/3G modem (different interface & ip) and want to continue on work in client appliaction. Note that application hasn't been closed.
User (client application) should be authenticated and if it is possible, communication should be encrypted.
What are the best practices?
Create new proxy for each operation? This should be very slow when initializing net.tcp connection with authentication.
Is solution basicHttp connection (+HTTPS) with InstanceContextMode.PerCall? Note that speed and higher payload is problem.
Or the best solution is something like "wrapper(Func<>)", which contains while loop until operation is successfully finished (on fail, new connection is created and function is called again).
Thanks you for suggestions
I've always kept the connection open for as long as the unit of work is necessary. Basically, the connection is only open and available while the application is performing some processing (and those processes require a WCF connection). It may be more overhead to keep reconnecting (and depending on connection speed it may add latency) but it's also more secure when it comes to having a connection to work with (least probability of failure) and I'm generally saving those resources for other purposes.
However, this all depends on what the application does; If the client is dumb and the service is doing all the work it may make sense to keep the connection as every function executes a method on the service. Though with that comes some failure checking and re-establishing should the connection be unexpectedly severed.
Also, netTcp is going to be a lot faster than wsHttp. And I personally haven't see a lot of latency on establishing a netTcp connection (though I don't know what kind of authentication you're doing [mine has generally implemented windows authentication])
I have always followed the guidance of try/Close/catch/Abort when it comes to a WCF proxy. I am facing a code base now that creates proxies in MVC controllers and just lets them go out of scope. I'm arguing the case that we need to edit the code base to use try/Close/catch/Abort but there is resistance.
Does anyone know a metric (e.g. perfmon) I can capture to illustrate the problem/benefit. Or a definitive reference that spells out the problem/benefit no one can dispute?
You can create a sample application to mimic the problem. Though I haven't tried you can try this,
Create a simple service and limit the maxConcurrentCalls and maxConcurrentSessions to 5.
Create a client application and in that, call the service method without closing the connection.
Fire up 6 or more clients
See what happens when you open a new connection from a client. Probably the client will wait for certain time and you get some exception.
If the client don't close the connection properly, the connection will still remain open in the service so what happens if 1000s of client connected to the service at a time and leave their connections open? The service has a limitation that it could server 'n' connections at a time and because of that the service can't handle any new requests from clients and that's why closing connections are very important.
I think you are aware about the using problem in WCF service. In my applications I close the WCF connections using an extension method as said in this thread.
Have you tried a simple 'netstat -N' from the command prompt both on server and client? Yoy are likely to see a lot of waiting/pending connections which might exhaust your server resources for no reason.
I got this question regarding web server (such as nginx, Cherokee or Oracle iPlanet) and Java containers (such as GlassFish): Can we control what happens to the connection if the user drops an unfinished connection?
When a browser opens an HTTP/HTTPS connection to a server, it hits the web server (nginx, Cherokee or Oracle iPlanet) and then reverse proxies to the Java container (GlassFish). The Java application then executes and does quite a lot of things such as calculation and finally needs to write to, say, 3 different databases. If it has finished writing to the 1st database - but not yet to the 2nd and 3rd database - and the user closes the connection (by closing the browser window, or looses a network connection, etc.) what will happen to the process?
Specifically, I would like the process to CONTINUE until it finishes executing all the code. I know of one way is to spin off the process on a new thread, but then this will incur computation costs. So, are there any settings/config I can do to make sure it will continue to execute even though the user has broken the connection?
With nginx, you can set proxy_ignore_client_abort on; and it will not close the connection to the backend if the client closes its connection.