Defines a Collector Plugin.

A Collector plugin will run in an independent process and will run the collect/1 function in a given frequency.

POAAgent app reads the Collectors configuration from the config.exs file when bootstrap and will create a process per each one of them. That configuration is referenced by :collectors key.

config :poa_agent,
   :collectors,
   [
     {name, module, frequency, label, args}
   ]

for example

config :poa_agent,
   :collectors,
   [
     {:my_collector, POAAgent.Plugins.Collectors.MyCollector, 5000, :my_metrics, [host: "localhost", port: 1234]}
   ]

name, module, frequency, label and args must be defined in the configuration file.

• name: Name for the new created process. Must be unique
• module: Module which implements the Collector behaviour
• frequency: time in milliseconds after which the function collect/1 will be called
• label: The data collected will be prefixed with this label. ie {:eth_metrics, "data"}
• args: Initial args which will be passed to the init_collector/1 function

In order to work properly we have to define in the configuration file also the mapping between the Collector and the Transfers related with it. A Transfer is a Plugin process which transfers the data to outside the agent node (external Database, Dashboard server…).

config :poa_agent,
     :mappings,
     [
       {collector_name, [transfer_name1, transfer_name2]}
     ]

for example

config :poa_agent,
     :mappings,
     [
       {:my_collector, [:my_transfer]}
     ]

Implementing A Collector Plugin

In order to implement your Collector Plugin you must implement 4 functions.

• init_collector/1: Called only once when the process starts
• collect/1: This function is called periodically after frequency milliseconds. It is responsible of retrieving the metrics
• metric_type/0: This function must return the metric type in string format (i.e “ethereum_metric”)
• terminate/1: Called just before stopping the process

This is a simple example of custom Collector Plugin

defmodule POAAgent.Plugins.Collectors.MyCollector do
  use POAAgent.Plugins.Collector

  def init_collector(args) do
    {:ok, :no_state}
  end

  def collect(:no_state) do
    IO.puts "I am collecting data!"
    {:transfer, "data retrieved", :no_state}
  end

  def metric_type do
    "my_metrics_type"
  end

  def terminate(_state) do
    :ok
  end

end