On Thu, Aug 29, 2013 at 5:20 PM, Simon King <si...@simonking.org.uk> wrote: > 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. >
Googling "mysql Waiting for table metadata lock" gives a few clues. This one looks like a nice short summary: http://www.chriscalender.com/?p=1189 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.
