[Ruby-DBI-devel] Locking problem

[Matthew B. <ma...@by...>]

Hello;

I've just noticed an undesirable interaction between multithreaded Ruby 
applications and the MySQL C API (if not other DB APIs); my web spider 
application was running along fine but suddenly after an unpredictable number 
of minutes, hours etc. it would stop dead.  I think the problem is that I use 
a "lock tables" statement which, if used with Ruby threads, blocks the whole 
Ruby process until the table is unlocked.  Trouble is if the 'thread' holding 
the lock is an internal Ruby thread in the same process it'll never get run 
to unlock it :-/

Is there a general way around this problem with the mysql_ API?  My 
impression is no, since I can't find any way of telling mysql to use 
non-blocking semantics through its C API.  Anyhow even if we leave it like 
this it's probably worth adding a note about this pitfall to the docs.

cheers,

-- 
Matthew Bloch                 Bytemark Computer Consulting
                                http://www.bytemark.co.uk/
                                  tel. +44 (0) 8707 455026