NewRelic agent for Elixir

Instrument your Phoenix applications with New Relic.

It currently supports instrumenting Phoenix controllers and Ecto repositories to record response times for web transactions and database queries.

Based on newrelic-erlang and new-relixir

Why yet another?

1. newrelic-erlang & new-relixir look abandoned, so the main goal is to create a maintainable integration with NewRelic open to pull requests.
2. newrelic-erlang has a performance issue related to statman usage. Look at a real-world example of new-relixir usage (the project handles about 25 rps):

The new_relic isn't suffer from such the leaks.

Usage

The following instructions show how to add instrumentation with New Relic to a hypothetical Phoenix application named MyApp.

1. Add new_relic to your list of dependencies and start-up applications in mix.exs:

   # mix.exs
   
   defmodule MyApp.Mixfile do
     use Mix.Project
   
     # ...
   
     def application do
       [mod: {MyApp, []},
        applications: [:new_relic]]
     end
   
     defp deps do
       [{:new_relic, "~> 0.1.2"}]
     end
   end

2. Add your New Relic application name and license key to config/config.exs. You may wish to use environment variables to keep production, staging, and development environments separate:

   # config/config.exs
   
   config :new_relic,
     application_name: System.get_env("NEWRELIC_APP_NAME"),
     license_key: System.get_env("NEWRELIC_LICENSE_KEY"),
     poll_interval: 60_000 # push data to NewRelic once per 1 minute

3. Define a module to wrap your repository's methods with New Relic instrumentation:

   # lib/my_app/repo.ex
   
   defmodule MyApp.Repo do
     use Ecto.Repo, otp_app: :my_app
   
     defmodule NewRelic do
       use Elixir.NewRelic.Plug.Repo, repo: MyApp.Repo
     end
   end

   Now MyApp.Repo.NewRelic can be used as a substitute for MyApp.Repo. If a Plug.Conn is provided as the :conn option to any of the wrapper's methods, it will instrument the response time for that call. Otherwise, the repository will behave the same as the repository that it wraps.

4. For any Phoenix controller that you want to instrument, add NewRelic.Plug.Phoenix and replace existing aliases to your application's repository with an alias to your New Relic repository wrapper. If instrumenting all controllers, update web/web.ex:

   # web/web.ex
   
   defmodule MyApp.Web do
     def controller do
       quote do
         # ...
         plug NewRelic.Plug.Phoenix
         alias MyApp.Repo.NewRelic, as: Repo # Replaces `alias MyApp.Repo`
       end
     end
   end

5. Update your controllers to pass conn as an option to your New Relic repo wrapper:

   # web/controllers/users.ex
   
   defmodule MyApp.UserController do
     use MyApp.Web, :controller
   
     def index(conn, _params) do
       users = Repo.all(User, conn: conn) # Replaces `Repo.all(User)`
       # ...
     end
   end

Instrumenting Custom Repo Methods

If you've defined custom methods on your repository, you will need to define them on your wrapper module as well. In the wrapper module, simply call your repository's original method inside a closure that you pass to instrument_db:

# lib/my_app/repo.ex

defmodule MyApp.Repo do
  use Ecto.Repo, otp_app: :my_app

  def custom_method(queryable, opts \\ []) do
    # ...
  end

  defmodule NewRelic do
    use NewRelic.Plug.Repo, repo: MyApp.Repo

    def custom_method(queryable, opts \\ []) do
      instrument_db(:custom_method, queryable, opts, fn() ->
        MyApp.Repo.custom_method(queryable, opts)
      end)
    end
  end
end

When using the wrapper module's custom_method, the time it takes to call MyApp.Repo.custom_method/2 will be recorded to New Relic.

Distributed under the MIT License.