Tracing: don't record HTTP OPTIONS and HEAD transactions

CHANGELOG.md

@@ -37,6 +37,10 @@
 
 - Pick up config.cron.default_timezone from Rails config ([#2213](https://github.com/getsentry/sentry-ruby/pull/2213))
 
+### Bug Fixes
+
+- Sentry will not record traces of HTTP OPTIONS and HEAD requests in Rack and Rails apps [#2181](https://github.com/getsentry/sentry-ruby/pull/2181)
+
 ## 5.15.2
 
 ### Bug Fixes

sentry-rails/lib/sentry/rails/action_cable.rb

@@ -3,6 +3,7 @@ module Rails
     module ActionCableExtensions
       class ErrorHandler
         OP_NAME = "websocket.server".freeze
+        IGNORED_HTTP_METHODS = ["HEAD", "OPTIONS"].freeze
 
         class << self
           def capture(connection, transaction_name:, extra_context: nil, &block)
@@ -33,6 +34,8 @@ def capture(connection, transaction_name:, extra_context: nil, &block)
           end
 
           def start_transaction(env, scope)
+            return nil if IGNORED_HTTP_METHODS.include?(env["REQUEST_METHOD"])
+
             options = { name: scope.transaction_name, source: scope.transaction_source, op: OP_NAME }
             transaction = Sentry.continue_trace(env, **options)
             Sentry.start_transaction(transaction: transaction, **options)

sentry-rails/lib/sentry/rails/capture_exceptions.rb

@@ -2,6 +2,7 @@
   module Rails
     class CaptureExceptions < Sentry::Rack::CaptureExceptions
       RAILS_7_1 = Gem::Version.new(::Rails.version) >= Gem::Version.new("7.1.0.alpha")
+      IGNORED_HTTP_METHODS = ["HEAD", "OPTIONS"].freeze
 
       def initialize(_)
         super
@@ -32,6 +33,8 @@
       end
 
       def start_transaction(env, scope)
+        return nil if IGNORED_HTTP_METHODS.include?(env["REQUEST_METHOD"])
+
         options = { name: scope.transaction_name, source: scope.transaction_source, op: transaction_op }
 
         if @assets_regexp && scope.transaction_name.match?(@assets_regexp)

sentry-ruby/lib/sentry/rack/capture_exceptions.rb

@@ -4,6 +4,7 @@ module Sentry
   module Rack
     class CaptureExceptions
       ERROR_EVENT_ID_KEY = "sentry.error_event_id"
+      IGNORED_HTTP_METHODS = ["HEAD", "OPTIONS"].freeze
 
       def initialize(app)
         @app = app
@@ -62,7 +63,18 @@ def capture_exception(exception, env)
       end
 
       def start_transaction(env, scope)
-        options = { name: scope.transaction_name, source: scope.transaction_source, op: transaction_op }
+        # Tell Sentry to not sample this transaction if this is an HTTP OPTIONS or HEAD request.
+        # Return early to avoid extra work that's not useful anyway, because this
+        # transaction won't be sampled.
+        # If we return nil here, it'll be passed to `finish_transaction` later, which is safe.
+        return nil if IGNORED_HTTP_METHODS.include?(env["REQUEST_METHOD"])
+
+        options = {
+          name: scope.transaction_name,
+          source: scope.transaction_source, 
+          op: transaction_op
+        }
+
         transaction = Sentry.continue_trace(env, **options)
         Sentry.start_transaction(transaction: transaction, custom_sampling_context: { env: env }, **options)
       end

sentry-ruby/spec/sentry/rack/capture_exceptions_spec.rb

@@ -178,6 +178,7 @@ def inspect
         expect(event.breadcrumbs.count).to eq(1)
         expect(event.breadcrumbs.peek.message).to eq("request breadcrumb")
       end
+
       it "doesn't pollute the top-level scope" do
         request_1 = lambda do |e|
           Sentry.configure_scope { |s| s.set_tags({tag_1: "foo"}) }
@@ -192,6 +193,7 @@ def inspect
         expect(event.tags).to eq(tag_1: "foo")
         expect(Sentry.get_current_scope.tags).to eq(tag_1: "don't change me")
       end
+
       it "doesn't pollute other request's scope" do
         request_1 = lambda do |e|
           Sentry.configure_scope { |s| s.set_tags({tag_1: "foo"}) }
@@ -295,6 +297,20 @@ def will_be_sampled_by_sdk
           verify_transaction_attributes(transaction)
           verify_transaction_inherits_external_transaction(transaction, external_transaction)
         end
+
+        context "performing an HTTP OPTIONS request" do
+          let(:additional_headers) do
+            { method: "OPTIONS" }
+          end
+
+          it "doesn't sample transaction" do
+            wont_be_sampled_by_sdk
+
+            stack.call(env)
+
+            expect(transaction).to be_nil
+          end
+        end
       end
 
       context "with unsampled trace" do