RailsDiscordNotifier

Send Rails exceptions to a Discord channel or a Google Chat space via an incoming webhook.

• Catches unhandled exceptions from web requests (Rack middleware) and from background jobs, rake tasks and runners (Rails.error subscriber, Rails 7.0+)
• Redacts secrets from params and query strings, using your app's own config.filter_parameters plus a built-in list
• Never slows down or breaks your app: delivery happens off the request thread, with short timeouts, and every failure is logged rather than raised
• Never floods your channel: repeats of the same error are collapsed, and routing/404-style noise is ignored by default

gem "rails_discord_notifier", "~> 0.3"

bundle install
rails generate rails_discord_notifier:install

Then set your webhook. The gem works out which service it is from the URL.

Discord: Server Settings → Integrations → Webhooks → Copy URL.

export DISCORD_WEBHOOK_URL="https://discord.com/api/webhooks/…/…"

Google Chat: open the space → Apps & integrations → Webhooks → Add webhook, then copy the URL. Your Workspace admin must allow incoming webhooks.

export GOOGLE_CHAT_WEBHOOK_URL="https://chat.googleapis.com/v1/spaces/…/messages?key=…&token=…"

The generated initializer reads DISCORD_WEBHOOK_URL, then GOOGLE_CHAT_WEBHOOK_URL. Treat either URL as a password: anyone holding it can post to your channel.

bundle exec rails_discord_notifier test

This posts a real sample report to your webhook and prints what the service said, so you find out now rather than during your next incident. It reads DISCORD_WEBHOOK_URL, then GOOGLE_CHAT_WEBHOOK_URL, or takes --webhook URL (which ends up in your shell history, so prefer the environment variable).

In Discord, an embed titled with the failing request, followed by the details you need to find the error:

Exception in POST /orders
ActiveRecord::RecordInvalid: Validation failed: Email can't be blank
Caused by ArgumentError: missing email

URL          https://shop.example.com/orders
Controller   orders          Action   create
Environment  production      Release  a1b2c3d
Request ID   8f3c…           Host     web-01
Params       { "order": { "email": "", "card_token": "[FILTERED]" } }
Backtrace    `app/controllers/orders_controller.rb:42:in 'create'` …

In Google Chat, the same details as a single text message, with the params and backtrace in code blocks. Chat has no per-message sender name or avatar: those come from the name and avatar you gave the webhook when you created it.

The backtrace goes through Rails.backtrace_cleaner, as on Rails' own error pages, so it shows your app's frames rather than gem internals. When an error never reaches your code, such as a job class that doesn't exist, the library frames are shown with short gem paths instead. On Heroku, Host is the dyno name (web.1, worker.2) rather than the dyno's random hostname.

Everything is optional except webhook_url.

RailsDiscordNotifier.configure do |config|
  config.webhook_url = ENV.fetch("DISCORD_WEBHOOK_URL", nil)
  config.release     = ENV.fetch("GIT_COMMIT_SHA", nil)

  config.ignored_exceptions += %w[MyApp::HarmlessError]

  config.context = ->(env) { { "User" => env&.dig("warden")&.user&.id } }
end

A missing or malformed webhook_url logs a warning and disables the notifier. It will never take down application boot.

ActionController::RoutingError, ActiveRecord::RecordNotFound, ActionController::InvalidAuthenticityToken, ActionController::UnknownFormat, ActionController::BadRequest, Rack::QueryParser::ParameterTypeError and similar client-caused errors. See Configuration::DEFAULT_IGNORED_EXCEPTIONS for the full list. Replace it wholesale with config.ignored_exceptions = [...] or extend it with +=.

Parameters and query strings are filtered recursively with ActiveSupport::ParameterFilter, using the union of:

1. your application's config.filter_parameters,
2. anything you add via config.filter_parameters, and
3. the gem's built-in list (passw, secret, token, _key, crypt, salt, certificate, otp, ssn, signature, authorization, cookie, session, credential).

Because it is a union, enabling this gem can never redact less than your application already does. The URL field leaves out the query string, so the query string is sent only as part of the filtered params. To leave out params and the query string, set config.include_params = false. An exception message that quotes a parameter value is still sent (see below). The same filter applies to extra fields from config.context and from Rails.error context.

Exception messages are free text rather than structured parameters, so they get a best-effort scrub instead: token=abc, password="x", Api_Key: abc, "password":"x", Authorization: Bearer abc and redis://:password@host style fragments are replaced with [FILTERED]. This catches the usual culprits (a database connection error carrying a password, an HTTP error carrying a URL with a token) but cannot be exhaustive the way parameter filtering is.

Path segments are sent as they are. If a route puts a secret in the path (for example /password_resets/:token), move it to the query string or the body, where it is filtered.

Request bodies, headers and cookies are never sent.

In Google Chat, text like <users/all> or <https://…|click here> would become an @all mention or a disguised link. Since anyone who can make your app raise controls part of the report (the path, the User-Agent, often the exception message), the gem defuses these with an invisible zero-width space after each <. The report looks the same but can't ping the space or hide a link. The space is still there if you copy text out of the report (for example in `<main>' from a backtrace), so retype the < if a search comes up empty.

Google Chat accepts about one message per second per space, shared with anything else posting there. Repeats of the same error are already collapsed (throttle_period), but a burst of different errors beyond that rate is rejected by Google with HTTP 429. Those rejections are logged, not retried.

rescue SomeError => e
  RailsDiscordNotifier.notify(e, context: { "Tenant" => tenant.id })
end

The middleware observes and re-raises, so it never changes how your application handles errors. When both entry points see the same exception, it is reported once.

"The same error" means the same exception class, raised from the same line, on the same controller action. So /orders/1 and /orders/2 failing the same way count as one error for throttle_period. At most 10 reports are delivered at once; during a storm, anything beyond that is dropped with a log line rather than starting more threads.

Asynchronous deliveries still in flight are waited for at process exit, so a report from a rake task or rails runner is not lost when the process ends. Call RailsDiscordNotifier.notifier.flush to wait for them explicitly.

Ruby 3.1+, Rails 6.1+. Every supported combination is exercised in CI.

bin/setup                 # install dependencies
bundle exec rspec         # run the test suite
bundle exec rubocop       # lint
bundle exec appraisal install && bundle exec appraisal rspec   # all Rails versions

To release: update lib/rails_discord_notifier/version.rb and CHANGELOG.md, then bundle exec rake release.

Bug reports and pull requests are welcome at https://github.com/gettinDrikkieWithIt/rails_discord_notifier. Please follow the Code of Conduct.

MIT. See LICENSE.txt.