Is there a log file analyzer for log4j files?

Take a look at Apache Chainsaw http://logging.apache.org/chainsaw/index.html for your needs

(disclaimer: I'm one of the developers contributing to Chainsaw V2)

Chainsaw V2 can provide some of the functionality you're looking for through its support for custom expressions and the ability to use those expressions to colorize, search and filter events.

You -can- load multiple log files into Chainsaw (by default, all events for a log file are placed on a logfile-specific tab). You can also define a 'custom expression logpanel' which will aggregate events from all tabs into a new tab matching an expression you provided - similar to a database 'view', you could use the expression 'LEVEL >= WARN' to collect all warnings, error & fatal messages from any log file into a single view.

Some example expressions which could be used to colorize, search or filter events:

• msg like 'User [a-z]* logged in'
• msg ~= login || msg ~= logout
• level > INFO
• exception exists
• timestamp <= '2010/04/06 15:05:35'

The only way to get 'counts' currently is to define an expression in the 'refine focus' field (the count of events matching the expression will show in the status bar).

One of the useful features added to the upcoming release is a clickable bar to the right of the table (similar to Eclipse or Idea's bar showing syntax error indications) which will display color rule and search expression matches for the entire log file.

When the next version of Chainsaw V2 comes out, I hope you give it a spin - it's Open Source, free, and we're always interested in suggestions & feedback.

I'd suggest Splunk. It provides fast, Google-like searching across lots (terabytes) of logs, is easy to filter (e.g. by log level or date), makes it easy to correlate into transactions of multiple related log events, etc.

There's a downloadable version that's free as long as you're indexing less than 500MB of logs per day.