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rstatsd

rstatsd is a daemon that takes the output of multiple commands and sends the output to statsd based on a regular expressions with optional named capture groups.

installation

It's not a gem yet. In the meantime, you can install rstatsd like this:

gem install statsd-client
git clone https://[email protected]/9minutesnooze/rstatsd.git

If you are running Ruby 1.8, you will also need to install the oniguruma gem and development headers.

Ubuntu 10.04

apt-get install libonig-dev libonig2
gem install oniguruma

OSX

sudo port install oniguruma4
gem install oniguruma

If you know how to easily install oniguruma on other platforms, let me know.

You will also need ps in your $PATH.

configuration

All configuration is done with a yaml file. A basic yaml file looks like this:

---
:logfile: "/var/log/rstatsd.log
:metric_prefix: "com.example.www."
- :cmd: "tail -F /var/log/nginx/blog_access.log"
  :regexes: 
  - :regex: '^.*$'
    :metrics: 
    - "blog.requests"
  - :regex: '(?<http_method>[A-Z]+)\s.*?\sHTTP/1\.1"\s(?<http_code>\d+)\s'
    :metrics: 
    - "blog"
:statsd: 
  :host: "graphite.example.com"
  :port: 8125

This will make rstatsd tail blog_access.log and check it against two regular expressions. The first regular expression ^.*$ will match everything and increment the metric com.example.www.blog (the com.example.www piece comes from the :metric_prefix). This will log all requests to statsd.

The second regex (?<http_method>[A-Z]+)\s.*?\sHTTP/1\.1"\s(?<http_code>\d+)\s uses named capture groups and is a little bit more complicated. It will use the name of the capture (http_method, http_code) as a parent metric name, and the value of the capture as the leaf of the metric name. In this example, that means that you will get statistics on the following metrics:

com.example.www.blog.http_method.GET
com.example.www.blog.http_method.POST
com.example.www.blog.http_method.HEAD
...

and

com.example.www.blog.http_code.200
com.example.www.blog.http_code.301
com.example.www.blog.http_code.302
com.example.www.blog.http_code.404
com.example.www.blog.http_code.500
...

Want to watch more than one commend? Just do it. rstatsd is multithreaded, so you can specify as many :cmd sections and as many regular expressions as you find interesting.

command line options

$ ./rstatsd.rb --help
Usage: ./rstatsd.rb [options]
    -d, --[no-]daemonize             Daemonize (default false)
    -c, --config FILE                Configuration file (default ./rstatsd.yaml)
    -p, --pidfile FILE               PID file (default /tmp/rstatsd.pid)
    -k, --command COMMAND            Command (start|stop|status)
    -h, --help                       Show this message

Start it, as a daemon with a config file in /etc

$ ./rstatsd.rb -c /etc/rstatsd.yaml -d -k start

Stop it

$ ./rstatsd.rb -k stop
I'm done
Killing pid 6540
Killing pid 6542
Killing pid 6544
Killing pid 6546
Killing pid 6548
Killing pid 6550
Killing pid 6552
Killing pid 6538

Is it running?

$ ./rstatsd.rb -k status
rstatsd.rb is running.
$ echo $?
1 
$ ./rstatsd.rb -k stop
...
$ ./rstatsd.rb -k status
rstatsd.rb is not running.
$ echo $?
1

limiting UDP calls

I originally wrote rstatsd to pull stats out of nginx logs that occur upwards of 60k times a minute. Even with UDP, that's kind of a lot of network traffic. To reduce the volume of UDP requests, you can add :every: n to a :cmd to only submit to statsd after every n lines.

For example,

- :cmd: "tail -F /var/log/nginx/blog_access.log"
  :every: 100
  :regexes:
  - :regex: '^.*$'
    :metrics:
    - "blog.requests"

This will only send data to statsd every 100 lines, thus reducing UDP traffic by 100x. Never make the :every value less than what you expect your minimum traffic will be per aggregation interval as defined in statsd and carbon.

ignore :metric_prefix

If you want a metric that does not append the :metric_prefix, put / in front of the metric name

:metric_prefix: "foo.bar."
...
- :regex: '^.*$'
  :metrics:
  - "request"     # will result in a metric named 'foo.bar.request'
  - "/request"    # will result in a metric named 'request'
...

other cool stuff

You can specify multiple :metrics per :regex so you can have an aggregate (multiple host) stat and also one specific to this host. Or for some other reason. But you can do it.

stuff I want to do, but haven't yet

  • When metrics are prefixed by a /, ignore the :metric_prefix
  • be able to make :metric_prefix take a Proc
  • write some tests
  • document the code
  • optional logging to carbon/graphite for self-contained metrics