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From boB Gage <bg...@ekosystems.com>
Subject Re: Unbound thread growth...
Date Thu, 30 Apr 2009 17:37:30 GMT

That's kind of how the original C++ code that I'm porting worked...

The various devices we use each have their own serial parameters (baud, 
stop/start/partity bits et al) so all have their own SerialAddress 
objects to open & close.    Each device handler (ie our code) has it's 
own codec factory -- so there's not a single shared one for all the 
devices to be discovered (that would be way too unwieldy for words).

I've tried re-using IoConnector objects and just change handlers, but 
the IoConnector.setHandler() method (IoService.java) complains bitterly 
if I assign a new handler to an existing connection.

I have eliminated the synchronized clauses as a source, and had my Java 
understanding expanded in the process.  :-)   One of the two unbound 
threads *is* caught in that quoted wait() call however.    Perhaps 
because we failed to flush a failed session before closing it???  [ the 
notify is in a flush ]

Thanks again!

Emmanuel Lecharny wrote:
> boB Gage wrote:
>> Hi again...
>> I am working on an application that has to discover serial devices 
>> from a large set of known devices (each represented by their own 
>> collection of ProtocolHandler, CodecFactory, Encoders, and Decoders).
>> In the process of doing this, I am running through a list of known 
>> protocols, for each I:
>>   Create an IoConnector and a SerialAddress
>>   Attempt to connect -- which eventually fails because this is the 
>> wrong protocol
>>   Cycle to the next & try it...
>> Eventually (assuming it's there to be found) the right combination is 
>> attempted and all is good.
>> BUT....   turn off that device (or attach something that doesn't 
>> match any of the known protocols) and you can see an unbound thread 
>> growth.
>> Each cycle through the discovery process above generates several 
>> (six-ish) threads, most of which die.    Two don't, and remain in a 
>> WAITING state forevermore.
>> According to JProfiler, they are:
>>   SerialConnector-#-idleStatusChecker created from 
>> org.apache.mina.transport.serial.SerialConnector.<init>()
>> and
>>   Thread-# created from 
>> org.apache.mina.core.session.IoSession.write(java.lang.Object)
>> The various numbers in the Thread-# names increment by 4 in the 
>> threads that are left behind after each cycle (ie 4 get created, 3 
>> die -- the same 3 by creation order) -- The SerialConnector numbers 
>> increment by one. (ie. none of the idleStatusChecker threads ever 
>> goes away)
>> So far I have seen no bound in the thread creation.  In the execution 
>> I am currently profilling, my baseline was way back at time =0:50 
>> with a thread count of 10.   I'm now at time=243:33 with a thread 
>> count of 463.
>> Any clues would be greatly appreciated!!!
> Hi boB,
> sorry for the latency...
> Why are you trying to connect each time to test the protocol for the 
> device ? You should be able to connect only once, and deal with the 
> different protocols in the Codec filter, switching from one codec to 
> the other until you get the right one, or ended without any match.
> Doing so, you should be able to avoid creating useless connectors...

boB Gage
Software Engineer
Merge Healthcare

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