huginn/app/models/agent_log.rb

class AgentLog < ActiveRecord::Base
  attr_accessible :agent, :inbound_event, :level, :message, :outbound_event

  belongs_to :agent
  belongs_to :inbound_event, :class_name => "Event"
  belongs_to :outbound_event, :class_name => "Event"

  validates_presence_of :agent, :message
  validates_numericality_of :level, :only_integer => true, :greater_than_or_equal_to => 0, :less_than => 5

  def self.log_for_agent(agent, message, options = {})
    log = agent.logs.create! options.merge(:message => message)
    if agent.logs.count > log_length
      oldest_id_to_keep = agent.logs.limit(1).offset(log_length - 1).pluck("agent_logs.id")
      agent.logs.where("agent_logs.id < ?", oldest_id_to_keep).delete_all
    end
    log
  end

  def self.log_length
    ENV['AGENT_LOG_LENGTH'].present? ? ENV['AGENT_LOG_LENGTH'].to_i : 100
  end
end