Redis instrumentation

gistfile1.rb

::Redis::Client.class_eval do

  # Support older versions of Redis::Client that used the method
  # +raw_call_command+.
  call_method = ::Redis::Client.new.respond_to?(:call) ? :call : :raw_call_command

  def call_with_stats_trace(*args, &blk)
    method_name = args[0].is_a?(Array) ? args[0][0] : args[0]
    start = Time.now
    begin
      call_without_stats_trace(*args, &blk)
    ensure
      METRICS.timing("#{Thread.current[:stats_context] || 'wild'}.redis.#{method_name.to_s.upcase}.query_time", 
                       ((Time.now - start) * 1000).round, 1) rescue nil
    end
  end

  alias_method :call_without_stats_trace, call_method
  alias_method call_method, :call_with_stats_trace

end if defined?(::Redis::Client)

This is the way that I prefer to monkey patch things. I find it very rare where Module#alias_method is actually required.

module StatsCollector
  call_method = ::Redis::Client.method_defined?(:call) ? :call : :raw_call_method
  define_method(call_method) do |*args, *blk|
    method_name = args[0].is_a?(Array) ? args[0][0] : args[0]
    start = Time.now
    begin
      super(*args, &blk)
    ensure
      METRICS.timing("#{Thread.current[:stats_context] || 'wild'}.redis.#{method_name.to_s.upcase}.query_time",
                       ((Time.now - start) * 1000).round, 1) rescue nil
    end
  end
end

redis = Redis.new(:host => '127.0.0.1', :port => 6379, :password => 'xyz')
redis.extend(StatsCollector)
redis.set('foo', '1')