Andreas Steinmetz writes:
> Hi,
> well, the query is over a network. Single switch with two VLANs between the
> systems, network speed is *200MBit/s*. The php code structure executing was:
>
> ... prepare query ...
> mysql_connect();
> mysql_query();
> mysql_fetch_row();
> mysql_close();
> ... process and send data to browser ...
>
> The table the query executed on did have a total of about 25000 rows at that
> time. The query executing had to return exacty one row (max()). When the query
> thread did terminate all threads waiting for inserts did keep *hanging* either
> in state 'System lock' or state 'Opening table'. Thus:
>
> The whole database was *deadlocked* with only insert queries pending after a
> a data retrieval query thread did execute. In this state a regular shutdown
> of the database is *not* possible, you have to send SIGTERM to shut down
> mysql. Oh, the same thing did happen *again* today.
>
> The behaviour looks like in some cases mysql doesn't unlock after a data
> retrieval query or that pending inserts don't get properly restarted.
>
> As a hint the inserting daemons keep continously connected to mysql as long as
> the database is up, there are automatic reconnect attempts in case the database
> is not available.
>
> To finally assert that replication isn't involved I'm running this now with the
> slaves stopped.
>
> If it happens again I will try to set up code that is able to reproduce the
> problem on a test system (single database without replication there).
>
HI!
Did INSERT queries changed their state after SELECT has finished
sending data ??
What OS is that and is there anything in the error log file that might
indicate some problems ??
If you are using Linux, there could be some problems with fast
Ethernet cards in duplex mode. If that is a case, please try disabling
duplexing (on hubs and switches). Also enable compression.
And yes, we would be very much interested in repeatable test case.
Regards,
Sinisa
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