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Entry  01 Sep 2009, Jimmy Ngai, Forum, Timeout during run transition 
    Reply  03 Sep 2009, Stefan Ritt, Forum, Timeout during run transition 
Message ID: 625     Entry time: 03 Sep 2009     In reply to: 624
Author: Stefan Ritt 
Topic: Forum 
Subject: Timeout during run transition 
> Dear All,
> I'm using SL5 and MIDAS rev 4528. Occasionally, when I stop a run in odbedit, 
> a timeout would occur: 
> [midas.c:9496:rpc_client_call,ERROR] rpc timeout after 121 sec, routine 
> = "rc_transition", host = "computerB", connection closed
> Error: Unknown error 504 from client 'Frontend' on host computerB
> This error seems to be random without any reason or pattern. After this error 
> occurs, I cannot start or stop any run. Sometime restarting MIDAS can bring 
> the system working again, but sometime not.
> Another transition timeout occurs after I change any ODB value using the web 
> interface:
> [midas.c:8291:rpc_client_connect,ERROR] timeout on receive remote computer 
> info: 
> [midas.c:3642:cm_transition,ERROR] cannot connect to client "Frontend" on host 
> computerB, port 36255, status 503
> Error: Cannot connect to client 'Frontend'
> This error is reproducible: start run -> change ODB value within webpage -> 
> stop run -> timeout!

A few hints for debugging:

- do the run stop via odbedit and the "-v" flag, like

[local:Online:R]/> stop -v

then you see which computer is contacted when.

- Then put some debugging code into your front-end end_of_run() routine at the 
beginning and the end of that routine, so you see when it's executed and how long 
this takes. If you do lots of things in your EOR routine, this could maybe cause a 

- Then make sure that cm_yield() in mfe.c is called periodically by putting some 
debugging code there. This function checks for any network message, such as the 
stop command from odbedit. If you trigger event readout has an endless loop for 
example, cm_yield() will never be called and any transition will timeout.

- Make sure that not 100% CPU is used on your frontend. Some OSes have problems 
handling incoming network connections if the CPU is completely used of if 
input/output operations are too heavy.

- Stefan
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