Can a persistent cache file be shared by various instances?

[hvelarde]

I was trying to set only one persistent cache file among 2 instances but I got a lot of LogError exceptions when I tried to start the second one.

I just want to know if this is possible or not:

2017-08-30T19:28:50 ERROR zc.lockfile Error locking file /tmp/zeoclient-1.zec.lock; pid=10889
Traceback (most recent call last):
  File "/opt/plone/buildout/eggs/zc.lockfile-1.0.2-py2.7.egg/zc/lockfile/__init__.py", line 84, in __init__
    _lock_file(fp)
  File "/opt/plone/buildout/eggs/zc.lockfile-1.0.2-py2.7.egg/zc/lockfile/__init__.py", line 59, in _lock_file
    raise LockError("Couldn't lock %r" % file.name)
LockError: Couldn't lock '/tmp/zeoclient-1.zec.lock'

[jimfulton]

Nope. A ZEO client cache can only be used by a single process at a time.

[jamadden]

FWIW, RelStorage supports a cache-local-dir option that allows multiple instances to share the same cache directory. It's far from perfect (see zopefoundation/ZODB#163 for one), but it may be helpful to some.

[hvelarde]

thanks!