[AMQNET-381] ActiveMQ.NMS hangs sometimes due to concurrency problems while accessing static IDictionary

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.5.4
• Fix Version/s: 1.5.5, 1.6.0
• Component/s: NMS

Environment

Windows Server 2008

• Patch Info: Patch Available
• Assignee: Timothy A. Bish
• Reporter: Sergei Sokolov
• Created: 16/Apr/12 08:54
• Updated: 16/Apr/12 15:49
• Resolved: 16/Apr/12 15:49

Description

I've found that rarely .NET process consumes ~90% CPU. I got the dump file and I found that the problem is in Dictionary<>.FindEntry method:

2de9e5a4 71711819 System.Collections.Generic.Dictionary`2[[System.__Canon, mscorlib],[System.__Canon, mscorlib]].FindEntry(System.__Canon)
2de9e5c4 716937f5 System.Collections.Generic.Dictionary`2[[System.__Canon, mscorlib],[System.__Canon, mscorlib]].ContainsKey(System.__Canon)
2de9e5c8 2aabdade Apache.NMS.ActiveMQ.Transport.TransportFactory.FindTransportFactory(System.String)
2de9e614 2aabd983 Apache.NMS.ActiveMQ.Transport.TransportFactory.NewInstance(System.String)
2de9e680 2aabd865 Apache.NMS.ActiveMQ.Transport.TransportFactory.CreateTransportFactory(System.Uri)
2de9e6f0 2aabd73b Apache.NMS.ActiveMQ.Transport.TransportFactory.CreateTransport(System.Uri)
2de9e70c 2aabd4f1 Apache.NMS.ActiveMQ.ConnectionFactory.CreateActiveMQConnection(System.String, System.String)
2de9e7a0 2aabd40a Apache.NMS.ActiveMQ.ConnectionFactory.CreateActiveMQConnection()
2de9e7b8 2aabd3a8 Apache.NMS.ActiveMQ.ConnectionFactory.CreateConnection()

I've searched for the solution and found a good article of Tess Ferrandez, explaining the situation - http://blogs.msdn.com/b/tess/archive/2009/12/21/high-cpu-in-net-app-using-a-static-generic-dictionary.aspx

It seems that all access to static Dictionary classes should be synchronized. I've added lock statements in the TransportFactory class to all appropriate places.