Filtering

When you add Sentry to your app, you get a lot of valuable information about errors and performance. And lots of information is good -- as long as it's the right information, at a reasonable volume.

The Sentry SDKs have several configuration options to help you filter out events.

We also offer Inbound Filters to filter events in sentry.io. We recommend filtering at the client level though, because it removes the overhead of sending events you don't actually want. Learn more about the fields available in an event.

Filtering Error Events

Configure your SDK to filter error events by using the before_send callback method and configuring, enabling, or disabling integrations.

Using before_send

All Sentry SDKs support the before_send callback method. Because it's called immediately before the event is sent to the server, this is your last chance to decide not to send data or to edit it. before_send receives the event object as a parameter, which you can use to either modify the event’s data or drop it completely by returning null, based on custom logic and the data available on the event.

require "active_support/parameter_filter"

Sentry.init do |config|
  #...

  # this example uses Rails' parameter filter to sanitize the event payload
  # for Rails 6+
  filter = ActiveSupport::ParameterFilter.new(Rails.application.config.filter_parameters)
  # for Rails 5
  filter = ActionDispatch::Http::ParameterFilter.new(Rails.application.config.filter_parameters)
  config.before_send = lambda do |event, hint|
    filter.filter(event.to_hash)
  end
end

Note also that breadcrumbs can be filtered, as discussed in our Breadcrumbs documentation.

Event Hints

The before_send callback is passed both the event and a second argument, hint, that holds one or more hints.

Typically, a hint holds the original exception so that additional data can be extracted or grouping is affected. In this example, the fingerprint is forced to a common value if an exception of a certain type has been caught:

Sentry.init do |config|
  # ...
  config.before_send = lambda do |event, hint|
    if hint[:exception].is_a?(ActiveRecord::ConnectionNotEstablished)
      event.fingerprint = ["database-unavailable"]
    end

    event
  end
end

For information about which hints are available see hints in Ruby.

When the SDK creates an event or breadcrumb for transmission, that transmission is typically created from some sort of source object. For instance, an error event is typically created from a log record or exception instance. For better customization, SDKs send these objects to certain callbacks (before_send, before_breadcrumb or the event processor system in the SDK).

Using Hints

Hints are available in two places:

1. before_send / before_breadcrumb
2. eventProcessors

Event and breadcrumb hints are objects containing various information used to put together an event or a breadcrumb. Typically hints hold the original exception so that additional data can be extracted or grouping can be affected.

For events, hints contain properties such as event_id, originalException, syntheticException (used internally to generate cleaner stack trace), and any other arbitrary data that you attach.

For breadcrumbs, the use of hints is implementation dependent. For XHR requests, the hint contains the xhr object itself; for user interactions the hint contains the DOM element and event name and so forth.

Sentry.init do |config|
  # ...
  config.before_send = lambda do |event, hint|
    if hint[:exception].is_a?(ActiveRecord::ConnectionNotEstablished)
      event.fingerprint = ["database-unavailable"]
    end

    event
  end
end

Hints for Events

originalException

The original exception that caused the Sentry SDK to create the event. This is useful for changing how the Sentry SDK groups events or to extract additional information.

syntheticException

When a string or a non-error object is raised, Sentry creates a synthetic exception so you can get a basic stack trace. This exception is stored here for further data extraction.

Hints for Breadcrumbs

event

For breadcrumbs created from browser events, the Sentry SDK often supplies the event to the breadcrumb as a hint. This can be used to extract data from the target DOM element into a breadcrumb, for example.

level / input

For breadcrumbs created from console log interceptions. This holds the original console log level and the original input data to the log function.

response / input

For breadcrumbs created from HTTP requests. This holds the response object (from the fetch API) and the input parameters to the fetch function.

request / response / event

For breadcrumbs created from HTTP requests. This holds the request and response object (from the node HTTP API) as well as the node event (response or error).

xhr

For breadcrumbs created from HTTP requests made using the legacy XMLHttpRequest API. This holds the original xhr object.

Filtering Transaction Events

To prevent certain transactions from being reported to Sentry, use the traces_sampler or before_send_transaction configuration option, which allows you to provide a function to evaluate the current transaction and drop it if it's not one you want.

Using traces_sampler

Note: The traces_sampler and traces_sample_rate config options are mutually exclusive. If you define a traces_sampler to filter out certain transactions, you must also handle the case of non-filtered transactions by returning the rate at which you'd like them sampled.

In its simplest form, used just for filtering the transaction, it looks like this:

Sentry.init do |config|
  #...
  config.traces_sampler = lambda do |sampling_context|
    # transaction_context is the transaction object in hash form
    # keep in mind that sampling happens right after the transaction is initialized
    # for example, at the beginning of the request
    transaction_context = sampling_context[:transaction_context]

    # transaction_context helps you sample transactions with more sophistication
    # for example, you can provide different sample rates based on the operation or name
    op = transaction_context[:op]
    transaction_name = transaction_context[:name]

    case op
    when /http/
      case transaction_name
      when /health_check/
        0.0 # ignore health_check requests
      else
        0.1
      end
    else
      0.0 # ignore all other transactions
    end
  end
end

It also allows you to sample different transactions at different rates.

If the transaction currently being processed has a parent transaction (from an upstream service calling this service), the parent (upstream) sampling decision will always be included in the sampling context data, so that your traces_sampler can choose whether and when to inherit that decision. In most cases, inheritance is the right choice, to avoid breaking distributed traces. A broken trace will not include all your services. See Inheriting the parent sampling decision to learn more.

Learn more about configuring the sample rate.

Using before_send_transaction

Sentry.init do |config|
  # ...
  config.before_send_transaction = lambda do |event, _hint|
    # skip unimportant transactions
    if event.transaction == "/unimportant/healthcheck/route"
      # don't send the event to Sentry
      nil
    else
      # filter out SQL queries from spans with sensitive data
      event.spans.each do |span|
        span[:description] = '<FILTERED>' if span[:op].start_with?('db')
      end

      event
    end
  end
end