Re: Zope3 sessions and database conflicts
Christian Theune <[email protected]>
| Newsgroups | gmane.comp.web.zope.devel |
|---|---|
| Message-ID | <[email protected]> |
On 03/04/2010 11:08 PM, Ross Patterson wrote: > Hermann Himmelbauer <[email protected]> writes: > >> Hi, >> For quite some time I see messages like this in my z3.log: >> >> 2010-03-02T16:27:14 WARNING ZopePublication Competing writes/reads >> at /BSPSite/act/++vh++http:zis.act.at:80/bankneu/++/images/sponsor_logo.png: >> database conflict error (oid 0x063f, class BTrees.OOBTree.OOBucket, serial >> this txn started with 0x038484dc7d5ac044 2010-03-02 14:52:29.379960, serial >> currently committed 0x038484ff3c6b5455 2010-03-02 15:27:14.160763) > > I note the conflict happened when the request was just for an image. > I've seen this before under Zope2 when a PAS plugin was mis-using the > session machinery as a cache during authentication of the request. When > ever a session object is accessed it initiates a write transaction in > the ZODB. With most, if not all, authentication methods, when a user is > logged-in the auth tokens are included in every request which means > every request from the logged-in user invokes the authentication > machinery, including requests for images. Since every page load > involves multiple requests for page resources, the database gets > overwhelmed with write transactions which inevitably conflict. When the > write conflict occurs, the publisher appropriately retries the request > which multiplies the number of requests which multiplies the load which > increases the amount of time taken in processing requests which > multiplies the likelihood of write conflicts and your off to the races > in the wrong direction. > > So I'd suggest you find out what in a request for a simple resource > (images, non-dynamic CSS or JS) is initiating the write transaction by > invoking sessions. It's likely there's an inappropriate use of sessions > there. I remember one thing about sessions where just the access to the session would create a new session even if it was never touched. The API actually provides two invokations: one to get a session and create if not existing, the other got get a session and raise a KeyError instead of creating a new one. -- Christian Theune · [email protected] gocept gmbh & co. kg · forsterstraße 29 · 06112 halle (saale) · germany http://gocept.com · tel +49 345 1229889 0 · fax +49 345 1229889 1 Zope and Plone consulting and development _______________________________________________ Zope-Dev maillist - [email protected] https://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - https://mail.zope.org/mailman/listinfo/zope-announce https://mail.zope.org/mailman/listinfo/zope )