[ZODB-Dev] persistent client caches okay to use again in ZODB 3.9.6?

[Chris Withers]

On 12/10/2010 17:56, Jim Fulton wrote:
> Currently the only configuration "docs" are in the .xml Alan provided a link to.
>
> The best size will depend on the app.

Is there a downside to "too big", provided there's plenty of disk space 
free on the app servers?

> There are some docs in
> http://svn.zope.org/ZODB/trunk/doc/, although I don't know if they're accurate.

...yeah, those look a lot like the original docs that Guido(?) wrote.

> In ZODB 3.10, the cache tracing analysis tools actually work and produce
> meaningful numbers if you start tracing with an empty cache.

Okay, does that mean the stuff that's documented should be ignored for 
ZODB 3.9?

I went for the following in the end:

...
       cache-size 200Mb
       client     app
       wait       on
     </zeoclient>
     mount-point /
     cache-size       50000
     cache-size-bytes 500Mb

Any obvious issues with that?

One problem I did hit, though, was if I restarted an app server, I got:

   File 
"/var/buildout-eggs/ZODB3-3.9.6-py2.6-linux-i686.egg/ZODB/config.py", 
line 210, in open
     **options)
   File 
"/var/buildout-eggs/ZODB3-3.9.6-py2.6-linux-i686.egg/ZEO/ClientStorage.py", 
line 395, in __init__
     self._cache = self.ClientCacheClass(cache_path, size=cache_size)
   File 
"/var/buildout-eggs/ZODB3-3.9.6-py2.6-linux-i686.egg/ZEO/cache.py", line 
194, in __init__
     self._lock_file = zc.lockfile.LockFile(path + '.lock')
   File 
"/var/buildout-eggs/zc.lockfile-1.0.0-py2.6.egg/zc/lockfile/__init__.py", line 
76, in __init__
     _lock_file(fp)
   File 
"/var/buildout-eggs/zc.lockfile-1.0.0-py2.6.egg/zc/lockfile/__init__.py", line 
59, in _lock_file
     raise LockError("Couldn't lock %r" % file.name)
LockError: Couldn't lock '....zec.lock'

...and yet the app server came up fine. What does this error message imply?

The above did not, however, occur if I stopped and then started the app 
server...

Race condition?

Chris

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