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Send collectd metrics from Ruby.
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README.md

collectd

Gem Version

Allows you to send metrics to collectd from Ruby, by talking to the collectd network protocol, and sending stats periodicially to a network-aware instance of collectd.

Installation

Add this line to your application's Gemfile:

gem 'collectd'

And then execute:

$ bundle

Or install it yourself as:

$ gem install collectd

Setup

You need to have collectd load the network plugin, and listen on UDP port 25826 (so it's acting as a server):

# /etc/collectd.conf

LoadPlugin network

<Plugin "network">
  Listen "ff18::efc0:4a42"
</Plugin>

Usage

Specify a server to send data to:

Collectd.add_server(10, 'ff18::efc0:4a42', 25826)

Each server you add will receive all the data you push later. An interval of 10 is quite reasonable. Because of UDP and collectd's network buffering, you can set the interval to less than 10, but you won't see much benefit.

ruby-collectd gives you a free data collector out of the box, and it's a nice gentle introduction to instrumenting your app.

To collect memory and CPU statistics of your Ruby process, do:

Stats = Collectd.my_process(:woo_data)
Stats.with_full_proc_stats

In the first line, we set up a new plugin. my_process is the plugin name (magically handled by method_missing), and :woo_data is the plugin instance.

A plugin name is generally an application's name, and a plugin instance is a unique identifier of an instance of an application (i.e. you have multiple daemons or scripts running at the same time).

In the second line, with_full_proc_stats is a method provided by ruby-collectd that collects stats about the current running process. It makes use of polled gauges, which we talk about later.

Behind the scenes, with_full_proc_stats is using a simple interface you can use to instrument your own data.

Back in the first line we set up a plugin which we wanted to record some data on. with_full_proc_stats sets up types, which are a kind of data you are measuring (in this case CPU and memory usage).

You can do this yourself like this:

Stats = Collectd.my_daemon(:backend)

# Set counter absolutely
Stats.my_counter(:my_sleep).counter = 0
Stats.my_gauge(:my_gauge).gauge = 23 

loop do 
  # Increment counter relatively
  Stats.my_counter(:my_sleep).count! 5
  # Set gauge absolutely
  Stats.my_gauge(:my_stack).gauge = rand(40)
  sleep 5
end

(Don't worry if this doesn't make sense - gauges and counters are explained below)

You can also poll for your data, if you feel comfortable with that:

Stats.counter(:seconds_elapsed).polled_counter do
  Time.now.to_i
end

Test Application

To test if you're Ruby application is successfully sending metrics to CollectD, please use the revett/collectd-carbon Docker image (setup instructions in README).

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