如何增加WCF服务的并行连接数

Question

Our web application has performance problems which I am investigating. It uses a 4-tier architecture with a MVC4 webapp, WCF data service and SQLServer as DB. The data service does not really scale the requests although there are enough resources available. It seems that it only answers 10-12 requests in parallel and queues all others. I would like to see that it answers >100 requests simultaneously.

1. I tried to play around with all configuration values I found for this topic for WCF: system.net -> connectionManagement -> add maxconnection=100 serviceBehavior -> serviceThrottling -> maxConcurrentCalls/Instances/Sessions=100. No success.
2. I tried to use httpBinding as well as netTcpBinding where I found the parameter maxConnections and set it to 100. No success.
3. Is it WCF? I implemented a simple sleep.aspx webform that has 1s to return (using Thread.Sleep()). Same Result, only 10-12 Requests are answered within 1s, further requests are queued.
4. Is it .Net? I installed ActiveState Perl on the testmachine and wrote a little Perl script which does the same. Same Result, 10-12 Requests are answered directly, others are queued.
5. Is it Windows? I installed the Perl script on a Linux machine with Apache. The test client runs under Windows. In this constellation I get 100 responses within 1s when I configure Apache to have as many server processes.
6. IIS is also able to run with multiple processes instead of multiple threads (Web garden) as well. Ah, in this case, IIS also answers 100 requests in parallel.

All this brings me to the conclusion that a single Windows process might not be able to handle more than 10-12 TCP connection in parallel.

Is this the truth? Can this be configured somewhere?

Due to the design of the data service it should not run with multiple processes because it uses an object cache which needs to be synchronized with all other instances.

Google seems not to know much about this issue.

Environment: Windows Server 2008 R2/Windows Server 2012 R2, MVC4, WCF, .Net 4.5.1

Thomy

Answer 1

 <serviceBehaviors>
     <behavior name="defaultServiceBehavior">
          <serviceThrottling maxConcurrentCalls="100" 
                 maxConcurrentInstances="100" maxConcurrentSessions="100" />
     </behavior>
 </serviceBehaviors>

Here's a summary of these settings:

maxConcurrentCalls: defines the maximum number of messages actively processed by all the service instances of a ServiceHost. The default value is 16. Calls in excess of the limit are queued.

maxConcurrentInstances: defines the maximum number of service instances that can execute at the same time. The default value is Int32.MaxValue. Requests to create additional instances are queued and complete when a slot below the limit becomes available.
maxConcurrentSessions: defines the maximum number of sessions that a ServiceHost instance can accept at one time. The default value is 10. The service will accept connections in excess of the limit, but only the channels below the limit are active (messages are read from the channel).

Answer 2

There are several things you can try

Add a service behaviour in to max out the amount of calls it can handle

  <serviceBehaviors>
    <behavior name="StandardServiceBehavior">
      <serviceThrottling maxConcurrentCalls="1000" maxConcurrentInstances="1000" maxConcurrentSessions="10000"/>
    </behavior>
 </serviceBehaviors>

Have you tried playing around with the Concurrency mode in the service behaviour?

maybe setting the service behaviour to

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple)]

see the full explanation to what this setting does here.

http://msdn.microsoft.com/en-us/library/system.servicemodel.concurrencymode(v=vs.110).aspx

You might also want to try adding in some logging for your wcf service, see this link

http://msdn.microsoft.com/en-us/library/ms730064(v=vs.110).aspx

It should give you a deeper insight into what is actually going on and whether there are any errors. Also sometimes I have seen if the maxconcurrentcalls has been hit it will queue the calls to the service, these are displayed as warnings.