[ic] Interchange / MySQL lockups

[Aaron Berg]

Hi all,

I've been encountering occasional lockups with an interchange
instance. Possibly a MySQL issue, possibly an Interchange issue.

The details:

Interchange 5.4.0
About 30 catalogs - the busiest gets about 15,000 unique visitors each month.
Database is MySQL 4.1.9
RedHat Enterprise
Perl 5.8.7 - non threaded

What we've observed is that some queries will just never finish.  In
mytop the query will show up for several minutes (with a status of
sleep) before it is killed. Restarting MySQL and / or interchange will
clear the list.

Interchange is running RPC mode with the following settings:
PreFork             Yes
StartServers        5
MaxServers          0
MaxRequestsPerChild 100
HouseKeeping        2
PIDcheck            120

The feeling I have from my troubleshooting too far is that we are
occasionally getting too many locked up MySQL queries at one time
which causes a huge backlog of queries waiting to be processed which
causes more hung queries.  Restarting MySQL or Interchange clears this
and the system works as normal.

Has anyone seen behavior similar to this?  Any pointers on where I
should look to narrow this down?

Thanks.