On Thu, Aug 29, 2013 at 4:48 PM, diverman <pa...@schon.cz> wrote: > Hi, > > we observed deadlock-like problem on our multi-component system with mysql > database. > > Our setup: > > 1) MySQL server 5.5 with many MyISAM tables Foo_<timestamp>, one per day > (like partitioning) > > 2) C++ backend daemon > * issuing CREATE TABLE IF NOT EXISTS Foo_<timestamp> (...) once per day > after midnight > * filling those tables with INSERT INTO Foo_<timestamp> during intraday > > 3) pythonic multi-threaded backend daemon (we call it 'worker') > * reads Foo_<timestamp> tables every minute via ScopedSession and mapped > classes 'Foo' > * fills memcache with statistics computed from Foo_* tables > > 4) pythonic/apache/mod_wsgi single-threaded, multi-process webserver > * runs also on shared codebase 'foobar', so it uses also ScopedSession > (same as 'worker') > * codebase is same when runing in webserver-mode and when running in > worker-mode (ScopedSession is always used). > > We observed that during rollover to next day the C++ BE daemon is blocked on > 'Waiting for table metadata lock: CREATE TABLE IF NOT EXISTS Foo_xxxxxxxxx > (...)' > > Webserver is also blocked. Kill the 'worker' helps, all blocked stuff > continues. If anyone could know: > > - why it blocks since we have MyISAM,which are transaction-less > - why the worker is the blockator, since it only executes SELECTs > - how to fix it? >
This sounds like more of a MySQL issue than an SQLAlchemy issue, so you might have more luck on a MySQL mailing list. In answer to your first question, http://dev.mysql.com/doc/refman/5.5/en/metadata-locking.html suggests that non-transactional tables can also be involved in metadata locks. I'm afraid I can't help with the rest. Simon -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/groups/opt_out.
