python - Tornado adbapi callback not running -

i'm afraid i'm finding difficult work adbapi interface sqlite3 connectionpools in twisted.

i've initialized pool in file i've named db.py:

from twisted.enterprise import adbapi   pool = adbapi.connectionpool("sqlite3", db=config.db_file) pool.start()   def last(datatype, n):     cmd = "select * %s order timestamp desc limit %i" % (datatype, n)     return pool.runquery(cmd) 

then, i'm importing db.py , using inside particular route handler. unfortunately, appears callback never triggered. datatype printed, response never printed.

class datahandler(tornado.web.requesthandler):      @tornado.web.asynchronous     def get(self, datatype):         print datatype         data = db.last(datatype, 500)         data.addcallback(self.on_response)      def on_response(self, response):         print response         self.write(json.dumps(response))         self.finish() 

any ideas?

mixing tornado , twisted requires special attention. try this, first lines executed in entire program:

import tornado.platform.twisted tornado.platform.twisted.install() 

then, start server:

tornado.ioloop.ioloop.current().start() 

what's happening is, start tornado ioloop never start twisted reactor. twisted sqlite connection begins io operation when run query, since reactor isn't running, operation never completes. in order ioloop , reactor share process must run 1 of them on top of other. tornado provides compatibility layer allows that.