Logs and log rotation

Plone and Zope maintain a variety of log files. As with all log files, you need to rotate your logs or your server will die from lack of storage. Log rotation is a process of maintaining a set of historical log files while periodically starting the current log file anew.

Log types and locations

The buildout recipes that set up ZEO server and client components allow you to set the names and location of your log files. We'll describe below the common names and locations. If this doesn't match your situation, check your buildout's zeoserver and zope2instance sections.

ZEO server log

A ZEO server only maintains one log file, which records starts, stops and client connections. Unless you are having difficulties with ZEO client connections, this file is uninformative. It also typically grows very slowly - so slowly that you may never need to rotate it.

The ZEO server log for a cluster will typically be found under your buildout directory at var/zeoserver/zeoserver.log.

Client logs

Client logs are much more interesting and grow more rapidly. There are two kinds of client logs, and each of your clients will maintain both:

Access logs

A record of HTTP, WebDAV, and - if it's turned on - ftp accesses to the client. This resembles traditional web-server log files. Typical location of a client's access log is var/client#/Z2.log.

Event logs

Startup, shutdown and error messages. Event logs need attention so that errors are quickly discovered. Typical location of a client's event log is var/client#/event.log.

Log levels

You may set the verbosity level of access and event logs via the zope2instance sections for your clients. This isn't very useful for event logs, but can be very useful for access logs. The default verbosity level for access logs - WARN - creates an entry for every HTTP access. If you are recording HTTP accesses via your proxy server, you may change the access logging level to "ERROR" and dramatically slow the rate at which your access logs grow:

recipe = plone.recipe.zope2instance
z2-log-level = ERROR

Don't turn down the access log level until you've had a chance to tune up your proxy cache. Seeing which requests make it through to the ZEO client is very useful information when checking caching and load balancing.

Client log rotation

The basic option here is between using the ZEO client log rotation mechanisms built into Zope and using external mechanisms - such as the log-rotation facilities available on your server.

Plone 4.2.2+

Plone 4.2.2+ allows you to set a simple size-based mechanism for client log rotation.

The mechanism actually is built into Zope 2.12+ (used in Plone 4.0+), but there was no easy way to use it in a buildout until release 4.2.5 of plone.recipe.zope2instance. That recipe version ships with Plone 4.2.2+. We'll describe later a not-as easy mechanism for earlier 4.x series releases of Plone.

For Plone 4.2.2+, just add configuration settings like these to your buildout's zope2instance sections:

recipe = plone.recipe.zope2instance
event-log-max-size = 5 MB
event-log-old-files = 5
access-log-max-size = 20 MB
access-log-old-files = 10

This will maintain five generations of event logs of maximum five megabytes in size and 10 generations of 20 megabyte access logs.

For earlier versions of Plone in the 4.x series, you may use a custom log setup command to pass parameters to Zope:

recipe = plone.recipe.zope2instance
event-log-custom =
        max-size = 5mb
        old-files 5
access-log-custom =
        max-size = 20mb
        old-files 10

Other log rotation mechanisms

Unix-ish systems have several log rotation mechanisms available. Two common ones are newsyslog and logrotate. Both are well-documented. The critical thing you need to know for each is how to signal Zope that a log rotation has occurred, forcing it to reopen the log file. Zope will do this if you send the client process a USR2 signal.

For example, with logrotate, you can rotate a client's logs with a configuration like:

# rotate logs for client #2
/var/db/plone4/zeocluster/var/client2/event.log {
    rotate 5
       kill -USR2 `cat /var/db/plone4/zeocluster/var/client2/client2.pid`

Error alerts

Zope can email access log error messages. As with other logging instructions, this is done with an addition to client zope2instance sections of your buildout:

recipe = plone.recipe.zope2instance
mailinglogger =
      flood-level 10
      level error
      smtp-server localhost
      from errors@yourdomain.com
      to errors@yourdomain.com
      subject [My domain error] [%(hostname)s] %(line)s

For complete detail on configuration, see the mailinglogger documentation.