README.md

# New Relic's Elixir Agent

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The Open-Source Elixir Agent allows you to monitor your `Elixir` applications with New Relic. It helps you track transactions, distributed traces and other parts of your application's behavior and provides an overview of underlying [BEAM activity](https://github.com/newrelic/elixir_agent/wiki/BEAM-stats-page).

[View the Documentation](https://hexdocs.pm/new_relic_agent)

### Support Statement

New Relic has open-sourced this project to enable monitoring of `Elixir` applications. This project is provided AS-IS WITHOUT WARRANTY OR SUPPORT, although you can report issues and contribute to the project here on GitHub.

### Contributing

We'd love to get your contributions to improve the elixir agent! Keep in mind when you submit your pull request, you'll need to sign the CLA via the click-through using CLA-Assistant. If you'd like to execute our corporate CLA, or if you have any questions, please drop us an email at [open-source@newrelic.com](mailto:open-source@newrelic.com). 

## Installation

Install the [Hex package](https://hex.pm/packages/new_relic_agent)

Requirements:
* Erlang/OTP 22
* Elixir 1.9

```elixir
defp deps do
  [
    {:new_relic_agent, "~> 1.0"}
  ]
end
```

## Configuration

You need to set a few required configuration keys so we can authenticate properly.

#### Via Application config

```elixir
config :new_relic_agent,
  app_name: "My App",
  license_key: "license_key"
```

#### Via Environment variables

You can also configure these attributes via `ENV` vars, which helps keep secrets out of source code.

* `NEW_RELIC_APP_NAME`
* `NEW_RELIC_LICENSE_KEY`

## Telemetry-based Instrumentation

Some common Elixir packages are auto-instrumented via [`telemetry`](https://github.com/beam-telemetry/telemetry)

* [`Plug`](https://github.com/elixir-plug/plug): See [NewRelic.Telemetry.Plug](https://hexdocs.pm/new_relic_agent/NewRelic.Telemetry.Plug.html) for details.
* [`Phoenix`](https://github.com/phoenixframework/phoenix): See [NewRelic.Telemetry.Phoenix](https://hexdocs.pm/new_relic_agent/NewRelic.Telemetry.Phoenix.html) for details.
* [`Ecto`](https://github.com/elixir-ecto/ecto): See [NewRelic.Telemetry.Ecto](https://hexdocs.pm/new_relic_agent/NewRelic.Telemetry.Ecto.html) for details.
* [`Redix`](https://github.com/whatyouhide/redix): See [NewRelic.Telemetry.Redix](https://hexdocs.pm/new_relic_agent/NewRelic.Telemetry.Redix.html) for details.

## Agent Features

There are a few agent features that can be enabled via configuration. Please see the documentation for more information.

* [Logs In Context](https://hexdocs.pm/new_relic_agent/NewRelic.Config.html#feature/1-logs-in-context)
* [Infinite Tracing](https://hexdocs.pm/new_relic_agent/NewRelic.Config.html#feature/1-infinite-tracing)
* [Security Controls](https://hexdocs.pm/new_relic_agent/NewRelic.Config.html#feature?/1-security)

## Manual Instrumentation

#### Transactions

The `Plug` and `Phoenix` instrumentation automatically report a Transaction for each request.

These Transactions will follow across any process spawned and linked (ex: `Task.async`), but will _not_ follow a process that isn't linked (ex: `Task.Supervisor.async_nolink`).

To manually connect a Transaction to an unlinked process, you can use `NewRelic.get_transaction` and `NewRelic.connect_to_transaction`. See the docs for those functions for further details.

```elixir
tx = NewRelic.get_transaction()

spawn(fn ->
  NewRelic.connect_to_transaction(tx)
  # ...
end)
```

If you are using a `Task` to spawn work, you can use the pre-instrumented `NewRelic.Instrumented.Task` convienince module to make this easier. Just `alias` it in your module and all your Tasks will be instrumented. You may also use the functions directly.

```elixir
alias NewRelic.Instrumented.Task

Task.Supervisor.async_nolink(MyTaskSupervisor, fn ->
  # This process wil be automatically connected to the Transaction...
end)
```

#### Function Tracing

`NewRelic.Tracer` enables detailed Function tracing. Annotate a function and it'll show up as a span in Transaction Traces / Distributed Traces, and we'll collect aggregate stats about it. Install it by adding `use NewRelic.Tracer` to any module, and annotating any function with an `@trace` module attribute

```elixir
defmodule MyModule do
  use NewRelic.Tracer

  @trace :work
  def work do
    # Will report as `MyModule.work/0`
  end
end
```

#### Distributed Tracing

Requests to other services can be traced with the combination of an additional outgoing header and an `:external` tracer.

```elixir
defmodule MyExternalService do
  use NewRelic.Tracer

  @trace {:request, category: :external}
  def request(method, url, headers) do
    NewRelic.set_span(:http, url: url, method: method, component: "HttpClient")
    headers = headers ++ NewRelic.distributed_trace_headers(:http)
    HttpClient.request(method, url, headers)
  end
end
```

#### Pre-Instrumented Modules

`NewRelic.Instrumented.Mix.Task` To enable the Agent and record an Other Transaction during a `Mix.Task`, simply `use NewRelic.Instrumented.Mix.Task`. This will ensure the agent is properly started, records a Transaction, and is shut down.

```elixir
defmodule Mix.Tasks.Example do
  use Mix.Task
  use NewRelic.Instrumented.Mix.Task

  def run(args) do
    # ...
  end
end
```

`NewRelic.Instrumented.HTTPoison` Automatically wraps HTTP calls in a span, and adds an outbound header to track the request as part of a Distributed Trace.

```elixir
alias NewRelic.Instrumented.HTTPoison
HTTPoison.get("http://www.example.com")
```

#### Other Transactions

You may start an "Other" Transaction for non-HTTP related work. This could used be while consuming from a message queue, for example.

To start an Other Transaction:

```elixir
NewRelic.start_transaction(category, name)
```

And to stop the Transaction within the same process:

```elixir
NewRelic.stop_transaction()
```

#### Adapters

There are a few adapters which leverage this agent to provide library / framework specific instrumentation. Note that these will eventually be replaced with `telemetry` based instrumentation.

* `Absinthe` https://github.com/binaryseed/new_relic_absinthe

#### Disabling

If you want to disable the agent, you can do it in two different ways:

* Application config: `config :new_relic_agent, license_key: nil`
* Environment variables: `NEW_RELIC_HARVEST_ENABLED=false`