[ZODB-Dev] Wrong blob returned in one of the zeo clients

[Maurits van Rees]

Op 18-02-11 15:34, Maurits van Rees schreef:
> Hi,
>
> I saw something strange today.  I have two zeo clients using the same
> database.  Both clients are on their own machine, and the database is
> also on a different one.  When looking at an image, one client showed a
> completely different image than the other.
>
> This is with RelStorage 1.5.0b2 (postgres), ZODB3 3.8.6-polling, Plone
> 3.3.5, with plone.app.blob 1.3.  The blobs are stored in RelStorage and
> the two zeo clients have their own blob cache with shared-blob-dir set
> to false.  This site has recently been migrated from file storage to
> relstorage and I have now migrated the images to blobs (using the
> migration from plone.app.blob).  This this a test setup btw, so not yet
> live.
>
> When I emptied the blob cache of the client that showed the wrong
> picture, it got the correct picture from the database.  Actually, I saw
> that the second client had only this single picture in its blob cache so
> I removed just this single picture from the blob cache of the first zeo
> client (that had the wrong one).
>
> Has anyone seen this behaviour before?
>
> Hm, I now see that the modification time of the wrong blob file as shown
> by the operating system is a time that is about halfway through the blob
> migration.  That might be an explanation, actually.
>
> Other ideas?

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).

I don't know a good way to reproduce this, so also hard to say if this 
would work better on the most recent ZODB3.

Perhaps 'experimental' *is* the right word for blob support in ZODB3 
3.8. ;-)


-- 
Maurits van Rees
Web App Programmer at Zest Software: http://zestsoftware.nl
Personal website: http://maurits.vanrees.org/