Saturday, February 17, 2007

threadsafe CheryPy

Using CherryPy is so easy, like everything in Python. But when running some pages with heavy SQL processing time, there are a lot of funny errors (malloc.. double free). Ooops, looks as something is not theadsafe. mySQLdb is not necessarily threadsafe, but cherrypy.engine.on_start_thread_list should handle this as suggested . Instead of digging deep into debugging, here is an alternative fix, using DBUtils.

Yipee, my code got posted into CherryPy:

import cherrypy
import MySQLdb

from DBUtils.PersistentDB import PersistentDB

class HomePage:
   @cherrypy.expose

   def index(self):
       sql = "select max(whatever) from bigtable;" #long running query

       c = persDb.connection().cursor()
       c.execute(sql)

       res = c.fetchone()
       c.close()
       return ' '.join( ['<html>', repr(res), '</html>'] )


cherrypy.tree.mount(HomePage())

if __name__ == '__main__': 
   persDb=PersistentDB(MySQLdb, 10000, host='localhost', db='db', passwd='****')

   cherrypy.config.update({'server.thread_pool': 10})
   cherrypy.server.quickstart()

   cherrypy.engine.start()
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