Logging in Zimbra Extensions

If you’re developing Zimbra extensions and have perhaps read my post about Zimbra Server debugging, you might be wondering about how to use logging in your extension.

Zimbra uses log4j for logging purposes – which is a quite common and comfortable way. Additionally, Zimbra offers a proxy class to handle logging for you. I will not tell you about things like severity levels here. You should have a fairly good idea about what logging is anyways.

To better separate logging for different areas, Zimbra has implemented a category system for logs. You can see the available categories in the Zimbra Wiki. So, embrace that category system and use the best category, when logging something.

The way to do that is by just statically calling the ZimbraLog utility class with the specific category, the severity, log message and maybe additional objects to print out. For example:

ZimbraLog.security.debug("User %s tries to authenticate.", acct);

As you can see, you can also use format signs (%s) to embed the provided objects into the log message. (There are actually a lot of message formats available. Check the log4j documentation for details)

To be able to actually see the log messages somewhere, you have multiple options:

• Add an account logger by calling
  zmprov addAccountLogger <account> <category> <severity>
Beware, though, that an account logger may not be available while your extension is called, as it is only availble in an account context (for example, when you’re logged in)
• Configure logging without restarting the mailboxd by editing the file ~zimbra/conf/log4j.properties and afterwards calling
  zmprov resetAllLoggers
Beware, though, that all changes are removed once the mailboxd is restarted.
• Configure a fixed logging setting by editing the file ~zimbra/conf/log4j.properties.in and restarting the mailboxd by calling
  zmmailboxdctl restart

The files log4j.properties{.in} expect the following entry format:

log4j.logger.zimbra.<category>=<severity>,<appender>

The „<appender>“ parameter relates to a appender-configuration, which is also configured in the same file and is used to writes log messages to specific files. For example, the „LOGFILE„-appender writes log messages to the file ~zimbra/log/mailbox.log, while the „AUDIT„-appender uses the file ~zimbra/log/audit.log.

While this is a bit complicated, it may help you determine the problem in your code without having to set up the debugging environment, which could be a bit nasty in a production environment.