[SNMP4J] Exception in thread "DefaultTCPTransportMapping": java.lang.ArrayIndexOutOfBoundsException

[Rodrigues, Rui 1. (NSN - PT/Amadora)]

Hello,

I'm using SNMP4J 1.11.1 in my application and the following error
happens several times:
DefaultTCPTransportMapping_10.50.51.195/0 ERROR (#28@) [STDERR]
Exception in thread "DefaultTCPTransportMapping_10.50.51.195/0" 
DefaultTCPTransportMapping_10.50.51.195/0 ERROR (#28@) [STDERR]
java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 93
DefaultTCPTransportMapping_10.50.51.195/0 ERROR (#28@) [STDERR]
at java.util.Vector.get(Unknown Source)
DefaultTCPTransportMapping_10.50.51.195/0 ERROR (#28@) [STDERR]
at
org.snmp4j.transport.TcpTransportMapping.fireConnectionStateChanged(TcpT
ransportMapping.java:132)
DefaultTCPTransportMapping_10.50.51.195/0 ERROR (#28@) [STDERR]
at
com.nsn.genmed.common.snmp.CustomTcpTransportMapping.access$1300(CustomT
cpTransportMapping.java:45)
DefaultTCPTransportMapping_10.50.51.195/0 ERROR (#28@) [STDERR]
at
com.nsn.genmed.common.snmp.CustomTcpTransportMapping$ServerThread.connec
tChannel(CustomTcpTransportMapping.java:838)
DefaultTCPTransportMapping_10.50.51.195/0 ERROR (#28@) [STDERR]
at
com.nsn.genmed.common.snmp.CustomTcpTransportMapping$ServerThread.run(Cu
stomTcpTransportMapping.java:749)
DefaultTCPTransportMapping_10.50.51.195/0 ERROR (#28@) [STDERR]
at java.lang.Thread.run(Unknown Source)

The application uses a single MultiThreadedMessageDispatcher (with 20
threads) and a single Snmp instance with this
MultiThreadedMessageDispatcher. A CustomTcpTransportMapping is used and
the code is identical to the DefaultTcpTransportMapping (we just added a
method to get some info abiut the sockets list).

The application handles 1500 connections to agents and there can have
connect and disconnect at the same for different agents. Each class
representing an agent implements TransportStateListener and is
registered in the TcpTransportMapping (so one can have 1500 listeners).

Looking at the code of
org.snmp4j.transport.TcpTransportMapping.fireConnectionStateChanged(Tran
sportStateEvent), I see that the code may not be thread safe... When
getting the listeners vector size, count can be equal to X listeners but
during the itereation, listeners may have been registered or
unregistered. And I think in my case, some listeners have been
unregistered meanwhile and ArrayIndexOutOfBoundsException is thrown.

if (transportStateListeners != null) {
      Vector listeners = transportStateListeners;
      int count = listeners.size();
      for (int i = 0; i < count; i++) {
        ((TransportStateListener)
         listeners.get(i)).connectionStateChanged(change);
      }
    }


Then the critical problem is that the exception is not catched anywhere
so the CustomTcpTransportMapping.ServerThread dies and all TCP
connections are lost and the application needs to be restarted.

I checked SNMP4J 11.1.2 and I don't see any fix for this.

Can you comment on this?
Thanks

One note: the application runs in a powerfull machine (with more than 30
CPUs/Cores) so we have a lot of multithreading/multiprocessing.

Best regards,
Rui Rodrigues