Tuesday, February 28, 2012

Announcing Project Lumberjack

Two weeks ago, along with the Fedora Developer's Conference in Brno, Czech Republic, a couple of logging and auditing folks from Red Hat, Balabit (syslog-ng), the MITRE Corporation, and Adiscon (me) stuck their heads together to talk about the future of structured logging. It quickly became clear that extending syslog in the CEE spirit is the right thing to do.

We observed that almost all technology is present to provide a rich framework to support structured logging. Actually, both syslog-ng and rsyslog provide the necessary plubming since long (for, example, as part of the RFC5424 effort), but that functionality is relatively seldom explored actively by other developers. A core problem in that regard is that most applications rely on the good old syslog() API, which does not provide structured logging by itself. Also, there is no common log storage database available, which tools could be based on.

In order to evolve syslog, we defined a three-layer architecture, with applications and logging libraries/APIs being the top layer, the syslogd the middle layer and the datastore the bottom layer. Multiple APIs must be supported as noone can expect projects to change their existing logging infrastructure. Also, existing frameworks like log4j or log4j and even glibc's syslog() will stay around for a while longer. New libraries (like ELAPI) will  probably become more dominant for new applications. So how to tie these different libraries to the syslogd subsystem (the second layer)?

The solution is rather simple: we use what we already achieved in CEE and support cee-enhanced syslog on the system log socket. The core idea is very simple: we use the regular syslog message part, but include JSON-encoded structured data with it. To signify to the syslog system that this is actually cee-enhanced, a cookie string ("@cee:") is used in front of the JSON data. It is then easy to decide for the syslogd which message format it deals with: if the cookie is present and the rest of the message is a valid JSON representation, the message is cee-enhanced. If one of the two conditions fails, it is traditional syslog. As both conditions are checked together, it is highly unlikely that a legacy syslog message will ever fit into that criteria (and if it really does, nothing is lost: after all, the syslogd has correctly understood that format). It must be noted that the necessary parsing and internal plumbin is available both in syslog-ng as well as rsyslog (I committed the missing JSON parser, held back awaiting a more final CEE standard, yesterday).

The interface to the log database layer is currently not as well defined and needs to be worked on. Note that both syslog-ng and rsyslog support multiple datastores, so there already exist solutions. The group as whole was of the opinion that some unified API for a log data store would be useful and something that should be looked at as a longer-term target.

After reaching this rough consensus, we were delighted to see that most of the base technology is already and place and just needs to be tied correctly together. It is more an effort of doing detail implementations and documenting the various pieces (and how they work exactly together) than creating a totally new system (aka "can be quickly done"). We agreed that it probably is best to reach for the low-hanging fruit first: get structured logging integrated first, then do the other steps. So an initial milestone will be making sure cee-enhanced syslog is supported by all of the subsystem and only after this is done reach for the other things.

One of these next things definitely is a dictionary of field names (and exact structure) to be used to describe events in a standard way (for example a logon event). While the whole effort is highly inspired by CEE, it probably is best to try out initial efforts outside of the formal CEE framework. That will enable rapid development, discussion and the capability to check what works in practice. The experience gained in such PoC can than be feed back to the formal CEE process (along the old IETF mantra "running code and rough consensus first").

We agreed that such an effort is best be done in a tranparent and flexible open source process. With that, project lumberjack was born: an effort to provide better structured logging for Linux, being supported by many major players in that arena. We agreed that it would be a good idea if Red Hat provided some of the project infrastructure. This is why you find project lumberjack now at fedorahosted.org (note that the project will probably contain mostly specs and less code, which is kept in the individual project's repositories).
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