Slack notifier

This notifier sends notifications to a slack channel using the slack-notifier gem.

Usage

Just add the slack-notifier gem to your Gemfile:

gem 'slack-notifier'

To configure it, you need to set at least the 'webhook_url' option, like this:

Rails.application.config.middleware.use ExceptionNotification::Rack,
                                        email: {
                                          email_prefix: '[PREFIX] ',
                                          sender_address: %{"notifier" <notifier@example.com>},
                                          exception_recipients: %w{exceptions@example.com}
                                        },
                                        slack: {
                                          webhook_url: '[Your webhook url]',
                                          additional_parameters: {
                                            icon_url: 'https://image.jpg',
                                            mrkdwn: true
                                          }
                                        }

The slack notification will include any data saved under env['exception_notifier.exception_data'].

An example of how to send the server name to Slack in Rails (put this code in application_controller.rb):

before_action :set_notification

def set_notification
  request.env['exception_notifier.exception_data'] = { 'server' => request.env['SERVER_NAME'] }
  # can be any key-value pairs
end

If you find this too verbose, you can determine to exclude certain information by doing the following:

Rails.application.config.middleware.use ExceptionNotification::Rack,
                                        slack: {
                                          webhook_url: '[Your webhook url]',
                                          channel: '#exceptions',
                                          additional_parameters: {
                                            icon_url: 'https://image.jpg',
                                            mrkdwn: true
                                          },
                                          ignore_data_if: lambda {|key, value|
                                            "#{key}" == 'key_to_ignore' || value.is_a?(ClassToBeIgnored)
                                          }
                                        }

Any evaluation to true will cause the key / value pair not be be sent along to Slack.

the slack-notifier gem allows to override the channel default value, if you ever need to send a notification to a different slack channel. Simply add the channel option when calling .notify_exception

ExceptionNotifier.notify_exception(
  exception,
  env: request.env,
  channel: '#my-custom-channel', # Make sure the channel name starts with `#`
  data: {
    error: error_variable,
    server: server_name
  }
)

If you ever need to add more slack-notifier specific options, and particularly to the #ping method of the slack notifier, you can use the pre_callback option when defining the middleware.

 pre_callback: proc { |opts, _notifier, _backtrace, _message, message_opts|
   message_opts[:channel] = opts[:channel] if opts.key?(:channel)
 }

message_opts is the hash you want to append to if you need to add an option.
options is the hash containing the values when you call ExceptionNotification.notify_exception

An example implementation would be:

config.middleware.use ExceptionNotification::Rack,
  slack: {
    webhook_url: '[Your webhook url]',
    pre_callback: proc { |opts, _notifier, _backtrace, _message, message_opts|
      message_opts[:ping_option] = opts[:ping_option] if
      opts.key?(:ping_option)
    }
  },
  error_grouping: true

Then when calling from within your application code:

ExceptionNotifier.notify_exception(
  exception,
  env: request.env,
  ping_option: 'value',
  # this will be passed to the slack notifier's `#ping`
  # method, as a parameter. The `:pre_callback` hook will catch it
  # and do that for you.
  # Helpful, if the API evolves, you only need to update
  # the `slack-notifier` gem
  data: {
    error: error_variable,
    server: server_name
  }
)

Options

webhook_url

String, required

The Incoming WebHook URL on slack.

username

String, optional

Username of the bot. Defaults to the name you set as such on slack

custom_hook

String, optional

Custom hook name. See slack-notifier for more information. Default: 'incoming-webhook'

additional_parameters

Hash of strings, optional

Contains additional payload for a message (e.g avatar, attachments, etc). See slack-notifier for more information.. Default: '{}'

additional_fields

Array of Hashes, optional

Contains additional fields that will be added to the attachement. See Slack documentation.

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