Re: Connector: sessionCreated is not called (unstable behavior)

[Victor]

Hello,

I have finally found where the problem was. It was in my code:
I called ConnectionRequest.cancel() for a connection request in the 
"done" state. Now I added the check:

if (!connectionRequest.isDone()) {
    connectionRequest.cancel();
}

I think it would be great to add this check to ConnectionRequest class 
itself. Otherwise mina adds the request to cancelQueue, but in fact 
there is nothing to cancel - that's why the Connector's run() loop works 
incorrectly.
What do you think?

Thanks,

Victor


Victor wrote:
Just a question:

why does Connector.run() thread exit when nHandles==0? Why not to 
continue executing select() in the loop infinitely?

Thanks,
Victor


Victor wrote:

Unfortunately, even with the patch in Connector and Processor, the 
problem is reproduced randomly, most of time everything works, but 
sometimes I see that sessionCreated is not called. But if I start a 
new connection, this "old" pending connection (for which I am waiting 
for sessionCreated callback) is completed instantly, so I get 
sessionCreated.

Victor N


Victor wrote:

I have added a similar fix in 
AbstractPollingIoProcessor.Processor.run() - nSessions is now 
initialized inside the loop, on each iteration.

It seems to work now, I can not reproduce the bug, but I will 
continue testing.
Not sure whether this patch is adequate or nor. Any comments?

Victor N


Victor wrote:
I tried to play with my fix - from the first glance, it seemed to 
work - connection was established, sessionCreated was called,
but at the second attempt the problem reproduced.

Any ideas what is wrong here?

Thanks,
Victor N


Victor wrote:

Hello,

I have a problem with NIO connector in mina 2.0 M4 when handling 
many simultaneous connections - sometimes after calling connect() I 
do not receive sessionCreated() callback.

I am trying to prepare a small test, but I can not reproduce the 
problem in this test yet, so I tried to investigate mina sources 
myself using out working system.

I can see that a new Channel is always created, channel.connect() 
is called, SYN, SYN-ACK, ACK are sent, then I see that 
AbstractPollingIoConnector.Connector registers the new channel in 
Selector, but after that AbstractPollingIoConnector.Connector is 
stopped because nHandles=0 and connectQueue is already empty (no 
more connection requests).

I mean the following code in 
AbstractPollingIoConnector.Connector.run():

if (nHandles == 0) {
    synchronized (lock) {
        if (connectQueue.isEmpty()) {
            connector = null;
            break;
        }
    }
}

After that, 'select' is not called on the Selector anymore for this 
session.

One reason of this behavior (which I can assume now) is 'nHandles' 
variable initialized outside of 'while' loop. Maybe, it should be 
initialized on each iteration? So every time we calculate the 
number of new sessions, canceled sessions, etc.
In my situation, nHandles=-1, then, after registering the new 
session, nHandles becomes 0 and the Connector.run() is stopped.


Victor N