Having Fun with ZEO

While it's cold (for our standards) with even a bit of snow on the higher hills around town, I'm having fun with ZEO. The thing is, I've got to run a one-off script in one of our instance, doing a catalog query and changing something on every found object. This is ideal to do with a plain old Python Script in the ZMI... except of course I have blocked any attempts to change those objects except through properly secured filesystem code.

Now I could change the permission and restart Zope and edit the objects and go back... and in the process kick out all users twice for the downtime. Don't like. Our ZEO setup offers a fun way of doing this without bothering users:

Because our setup is sporting one ZEO server hosting the same ZODB to multiple Zope instance, I did the code change / restart / edit / code change back / restart cycle only on that instance. The other instance, the one where most of the users are working on remained unchanged. It continued to run with the unchanged code, it wasn't restarted. The result: I got my job done, nobody noticed.

This is no big news for people who use ZEO intensely, some people even keep one Zope instance set up at hand for just those cases. That Zope instance doesn't even need to be constantly running. Another often seen trick is to update instances in round robin fashion, moving users without anybody noticing to different instances. Can't do that when the objects or their APIs have changed too much, but for most of the cases it works just fine.