BoomNotifier

---

This package allows your Phoenix application to send notifications whenever an exception is raised. By default it includes an email and a webhook notifier, you can also implement custom ones, or use some of the independently realeased notifiers listed below.

It was inspired by the ExceptionNotification gem that provides a similar functionality for Rack/Rails applications.

You can read the full documentation at https://hexdocs.pm/boom_notifier.

Installation

The package can be installed by adding boom_notifier to your list of dependencies in mix.exs:

def deps do
  [
    {:boom_notifier, "~> 0.8.0"}
  ]
end

Getting started

This is an example for setting up an email notifier, you can see the full list of available notifiers here.

Email notifier

BoomNotifier has built in support for both Bamboo and Swoosh.

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
      notifier: BoomNotifier.MailNotifier.Bamboo,
      # or to use Swoosh
      # notifier: BoomNotifier.MailNotifier.Swoosh,
      options: [
        mailer: YourApp.Mailer,
        from: "me@example.com",
        to: "foo@example.com",
        subject: "BOOM error caught"
      ]

  # ...

For the email to be sent, you need to define a valid mailer in the options keyword list. You can customize the from, to and subject attributes.

subject will be truncated at 80 chars, if you want more add the option max_subject_length.

Notifiers

BoomNotifier uses notifiers to deliver notifications when errors occur in your applications. By default, 2 notifiers are available:

• Email notifier
• Webhook notifier

You can also choose from these independetly-released notifiers:

• Slack notifier

On top of this, you can easily implement your own custom notifier.

Multiple notifiers

BoomNotifier allows you to setup multiple notifiers, like in the example below:

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    notifiers: [
      [
        notifier: BoomNotifier.WebhookNotifier,
        options: [
          url: "http://example.com",
        ]
      ],
      [
        notifier: CustomNotifier,
        options: # ...
      ]
    ]

Notification Trigger

By default, BoomNotifier will send a notification every time an exception is raised.

However, there are different strategies to decide when to send the notifications using the :notification_trigger option with one of the following values: :always and :exponential.

Always

This option is the default one. It will trigger a notification for every exception.

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    notification_trigger: :always,
    notifiers: [
      # ...
    ]

Exponential

It uses a formula of log2(errors_count) to determine whether to send a notification, based on the accumulated error count for each specific exception. This makes the notifier only send a notification when the count is: 1, 2, 4, 8, 16, 32, 64, 128, ..., (2**n).

You can also set an optional max value.

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    notification_trigger: :exponential,
    notifiers: [
      # ...
    ]

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    notification_trigger: [exponential: [limit: 100]]
    notifiers: [
      # ...
    ]

Notification trigger time limit

If you've defined a triggering strategy which holds off notification delivering you can define a time limit value which will be used to deliver the notification after a time limit milliseconds have passed from the last error. The time counter is reset on new errors and only applies for cases where notifications are not sent.

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    notification_trigger: [:exponential],
    time_limit: :timer.minutes(30),
    notifier: CustomNotifier

  # ...
end

Custom data or Metadata

By default, BoomNotifier will not include any custom data from your requests.

However, there are different strategies to decide which information do you want to include in the notifications using the :custom_data option with one of the following values: :assigns, :logger or both.

The included information will show up in your notification, in a new section titled "Metadata".

Assigns

This option will include the data that is in the connection assigns field.

You can also specify the fields you want to retrieve from conn.assigns.

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    custom_data: :assigns,
    notifiers: [
      # ...
    ]

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    custom_data: [assigns: [fields: [:current_user, :session_data]]],
    notifiers: [
      # ...
    ]

Example of adding custom data to the connection:

assign(conn, :name, "John")

Logger

This option will include the data that is in the Logger metadata field.

You can also specify the fields you want to retrieve from Logger.metadata().

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    custom_data: :logger,
    notifiers: [
      # ...
    ]

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    custom_data: [logger: [fields: [:request_id, :current_user]]],
    notifiers: [
      # ...
    ]

Example of adding custom data to the logger:

Logger.metadata(name: "John")

Using both

You can do any combination of the above settings to include data from both sources. The names of the fields are independent for each source, they will appear under the source namespace.

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    custom_data: [
      [assigns: [fields: [:current_user]]],
      [logger: [fields: [:request_id, :current_user]]]
    ],
    notifiers: [
      # ...
    ]
   # ...
end

Ignore exceptions

By default, all exceptions are captured by Boom. The :ignore_exceptions setting is provided to ignore exceptions of a certain kind. Said exceptions will not generate any kind of notification from Boom.

defmodule YourApp.Router do
  use Phoenix.Router

  use BoomNotifier,
    ignore_exceptions: [
      HTTPoison.Error, MyApp.CustomException
    ],
    notifiers: [
      # ...
    ]
   # ...
end

Implementation details

Boom uses Plug.ErrorHandler to trigger notifications. If you are already using that module you must use BoomNotifier after it.

Compatibility

This library aims to be compatible with Elixir versions from 1.10 to 1.17 although it might work with other versions.

License

BoomNotifier is released under the terms of the MIT License.

Credits

The authors of this project are Ignacio and Jorge. It is sponsored and maintained by Wyeworks.