On 03/01/2011 08:05 AM, Maurits van Rees wrote: > Op 01-03-11 13:54, Maurits van Rees schreef: >> Op 01-03-11 04:41, Shane Hathaway schreef: >>> On 02/28/2011 09:29 AM, Maurits van Rees wrote: >>>> This is now also happening for some images during normal operation, so >>>> after any blob migration has been run and existing blob caches have been >>>> cleared. What happens is that somehow the file contents for >>>> 0xblahblah.blob in the blob caches can differ between two zeo clients, >>>> even when the image has not changed at all (only tried with images as it >>>> is easier to spot than with other files). >>> >>> Thanks for the report. Looking through the blob code, I noticed that >>> when the system is using a blob cache, it was possible for a thread to >>> get a partial file while another thread is downloading that file. I >>> suspect this is the problem you saw. I have committed a fix. >> >> Thanks! I'll test this. > > No, I am still seeing it. I now see more clearly that the problem is > that two files share the same blob name. I completely remove the blob > cache and restart the zeo client. I visit image number 1 and get this > file in the var/blobcache: > 291/0x038c599924e70177.blob > > I then visit the second image and get served the same file! Now I > remove this file from the blob cache, load the second image in a browser > and this time I get the correct content for this image, using the same > file name in the var/blobcache directory. Now of course loading the > first image gives the wrong content. > > The .layout file is set to 'zeocache'. > > Any idea where the error might be? Could this be in plone.app.blob? > Any chance that this is better in ZODB 3.9+?
This appears to be a design bug in the "zeocache" blob layout: if a single transaction stores multiple blobs, and the OIDs of some of those blobs differ by a multiple of 997, then cache filenames will collide. I think the solution is to incorporate the OID, not just the transaction ID, in the cache filename. If I have diagnosed this correctly, this will have to be solved in ZEO as well. Nice catch! Shane _______________________________________________ For more information about ZODB, see the ZODB Wiki: http://www.zope.org/Wikis/ZODB/ ZODB-Dev mailing list - ZODB-Dev@zope.org https://mail.zope.org/mailman/listinfo/zodb-dev
