Hi, Thanks for the answer. The problem is that when create a Store object, storm does not try to connect right away so no exception is thrown at that point. When there is a need, storm try to use the connection and fail. To handle it, I have to wrap many try: catch exception all over places and not quite sure where and it does not look good. Like a php mysql db, they just don't care, if connection goes away, they reconnect / make new connection automatically. That would be be nice <div class="gmail_quote">On Wed, Jan 26, 2011 at 6:37 PM, Jamu Kakar <<a href="mailto:jkakar@kakar.ca">jkakar@kakar.ca</a>> wrote: <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hi Steve, <div class="im"> On Wed, Jan 26, 2011 at 9:31 AM, Steve Kieu <<a href="mailto:msh.computing@gmail.com">msh.computing@gmail.com</a>> wrote: > I am developing a simple WSGI application using storm and MySQL. The problem > is, after midnight ; or for some reason I restart MySQL server and my > application dies with 500 - and inside I have exception by Storm raised: > > [Sun Jan 23 08:23:10 2011] [error] [client 169.173.0.179] File > "/usr/local/lib/python2.6/dist-packages/storm/databases/mysql.py", line 106, > in execute > [Sun Jan 23 08:23:10 2011] [error] [client 169.173.0.179] return > Connection.execute(self, statement, params, noresult) > [Sun Jan 23 08:23:10 2011] [error] [client 169.173.0.179] File > "/usr/local/lib/python2.6/dist-packages/storm/database.py", line 227, in > execute > [Sun Jan 23 08:23:10 2011] [error] [client 169.173.0.179] > self._ensure_connected() > [Sun Jan 23 08:23:10 2011] [error] [client 169.173.0.179] File > "/usr/local/lib/python2.6/dist-packages/storm/database.py", line 344, in > _ensure_connected > [Sun Jan 23 08:23:10 2011] [error] [client 169.173.0.179] raise > DisconnectionError("Already disconnected") > > Sometimes I got the error mesasge like ; MySQL has gonna away .... </div>This is the expected behaviour. When the underlying database goes away (or is restarted) and an existing connection is used, Storm will raise a DisconnectionError. It's up to your application to detect this and determine how to recover. In the case of a web server you can usually just retry the request being handled. Be careful to put a maximum retry limit. If the database doesn't come back quickly you don't want to be continuously retrying requests. <div class="im"> > To fix, just restart apache. </div>This works because Storm is creating new connections to MySQL when you <div class="im">restart Apache. > The problem is that storm tried to use existing connection and the server is > gone. Storm does not want to reinitialize the connection but raise > exception. In my code it is clearly that for each request I create a dsn and > a Store object like store = Store(create_database(dsn)). Unfortunately it > still reuse the connection somehow and then dies. (probably the python > environment is reusing these variable somehow) </div>Storm will raise a DisconnectionError, as a signal that the transaction failed and you need to recover. If you try to use the connection again Storm will attempt to reconnect to the database automatically. If that fails, it'll raise DisconnectionError again. <div class="im"> > To prove that is the issue I took a cgi to wsgi gateway from python PEP > somewhere, fix it a bit so I can convert the whole wsgi to use cgi. Now > problem goes away, I can restart mysql server but the application still > works as expected. </div>Yep, this is because the CGI application is opening a new connection to the database for each request. If the database disappeared during the CGI request you'd see the same exception. Thanks, J. </blockquote></div> -- Steve Kieu