Monday, April 05, 2010

syslog-ng 3.2 opened, experimental "blocks" branch opened

After last the stable syslog-ng 3.1.0 release last week, I've opened the 3.2 branch to receive the new stuff. The first bits are already in the repository: the basic plugin framework and the conversion of the socket related stuff (tcp, udp, unix-dgram, unix-stream, syslog drivers) into a separate plugin.

The reason of the afsocket plugin conversion is to help moving the OpenSSL dependency to a separate package in distributions where this dependency cannot be associated with core packages like syslog-ng.

But I see a lot of potential behind the plugin framework, and I still have a lot of ideas, just check my last blog post in the topic.

Also, there's an even more experimental feature in the "blocks" branch right now, it is still incomplete, the naming and the syntax is still vague. The aim is there to provide syslog-ng.conf C++ template-like functionality in order to make the configuration easier by using pre-configured config snippets.

For example:

block source tomcat<root_dir="/opt/tomcat"> {
   file("<<root_dir>>/var/tomcat.log" follow_freq(1));
};

source s_local {
   tomcat(root_dir("/usr/local/tomcat"));
};

The idea is that if "tomcat" is referenced in a source statement, it'll be expanded to the content defined before that, all with proper argument passing and default values. This example actually works fine with the "blocks" branch right now.

Combining this feature with include files I foresee something like a "syslog-ng configuration library", which would contain pre-configured syslog-ng sources containing settings needed in order for a specific application to log properly, this way avoiding the hassle of integrating each and every application to syslog separately.

Another (not-yet-working) example would be to get rid off platform specific /dev/log declarations:

block source system<> {
@if (OS == "solaris")
@  if (OS_VERSION >= "10")
    sun-streams("/dev/log" door("/var/run/syslog_door"));
@  else
    sun-streams("/dev/log" door("/etc/.syslog_door"));
@  endif
@elif (OS == "linux")
    unix-dgram("/dev/log");
    file("/proc/kmsg" program_override("kernel"));
@elif (OS == ...)
    ...
@endif
};

source s_local { system(); };

This would make the initial configuration of syslog-ng much easier, and would allow you to use the same configuration file everywhere.

As I said this is still very experimental, I'm not yet sure about:
  • the name (I would have called these templates, but that is already taken in syslog-ng, just like "macro"). so if you have an idea of a better name I'd love hear about it
  • argument passing, whether to allow positional arguments
  • argument expansion syntax, "<<arg>>", and "$$arg" both occurred to me, the latter seems to be used more universally. I'd want to include both in strings (like in the example above) and in non-string arguments, e.g. follow-freq($$arg)
If you have comments, ideas for names, please post them as comments, or send an email to the syslog-ng mailing list.

Also, while I was there changing the parser/lexer framework for pluginization, I added more details to the error message to make it easier to locate the syntax error in the configuration file.

As for the next things, I'm going to start integrating the external contributions I've received so far, so stay tuned.

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