Add on_error settings for mysql2

docs/GettingStarted.md

@@ -1218,8 +1218,8 @@ client.query("SELECT * FROM users WHERE group='x'")
 |-----------------------|--------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------|
 | `service_name`        | `DD_TRACE_MYSQL2_SERVICE_NAME` | Name of application running the `mysql2` instrumentation. May be overridden by `global_default_service_name`. [See *Additional Configuration* for more details](#additional-configuration)                                                                                                                                                                              | `mysql2`     |
 | `peer_service`        | `DD_TRACE_MYSQL2_PEER_SERVICE` | Name of external service the application connects to                                                                                                                                                                                                                                                                                                                    | `nil`        |
-| `comment_propagation` | `DD_DBM_PROPAGATION_MODE`      | SQL comment propagation mode  for database monitoring. <br />(example: `disabled` \| `service`\| `full`). <br /><br />**Important**: *Note that enabling sql comment propagation results in potentially confidential data (service names) being stored in the databases which can then be accessed by other 3rd parties that have been granted access to the database.* | `'disabled'` |
-
+| `comment_propagation` | `DD_DBM_PROPAGATION_MODE`      | SQL comment propagation mode for database monitoring. <br />(example: `disabled` \| `service`\| `full`). <br /><br />**Important**: *Note that enabling SQL comment propagation results in potentially confidential data (service names) being stored in the databases which can then be accessed by other third parties that have been granted access to the database.* | `'disabled'` |
+| `on_error` | | Custom error handler invoked when MySQL raises an error. Provided `span` and `error` as arguments. Sets error on the span by default. Useful for ignoring errors that are handled at the application level. | `proc { \|span, error\| span.set_error(error) unless span.nil? }` |
 ### Net/HTTP
 
 The Net/HTTP integration will trace any HTTP call using the standard lib Net::HTTP module.

lib/datadog/tracing/contrib/mysql2/configuration/settings.rb

@@ -50,6 +50,10 @@ class Settings < Contrib::Configuration::Settings
               o.type :string, nilable: true
               o.env Ext::ENV_PEER_SERVICE
             end
+
+            option :on_error do |o|
+              o.type :proc, nilable: true
+            end
           end
         end
       end

lib/datadog/tracing/contrib/mysql2/instrumentation.rb

@@ -21,8 +21,9 @@ def self.included(base)
           module InstanceMethods
             def query(sql, options = {})
               service = Datadog.configuration_for(self, :service_name) || datadog_configuration[:service_name]
+              on_error = Datadog.configuration_for(self, :on_error) || datadog_configuration[:on_error]
 
-              Tracing.trace(Ext::SPAN_QUERY, service: service) do |span, trace_op|
+              Tracing.trace(Ext::SPAN_QUERY, service: service, on_error: on_error) do |span, trace_op|
                 span.resource = sql
                 span.span_type = Tracing::Metadata::Ext::SQL::TYPE
 

spec/datadog/tracing/contrib/mysql2/patcher_spec.rb

@@ -77,6 +77,20 @@
         end
 
         it_behaves_like 'with sql comment propagation', span_op_name: 'mysql2.query'
+
+        context 'when configured with `on_error`' do
+          before do
+            Datadog.configure_onto(client, on_error: ->(_span, _error) { false })
+          end
+
+          let(:sql_statement) { 'SELECT INVALID' }
+
+          it 'does not mark span with error' do
+            expect { query }.to raise_error(Mysql2::Error)
+
+            expect(span).not_to have_error
+          end
+        end
       end
 
       context 'when a successful query is made' do
@@ -149,6 +163,15 @@
         it_behaves_like 'configured peer service span', 'DD_TRACE_MYSQL2_PEER_SERVICE', error: Mysql2::Error do
           let(:configuration_options) { {} }
         end
+
+        context 'when configured with `on_error`' do
+          let(:configuration_options) { { on_error: ->(_span, _error) { false } } }
+
+          it 'does not mark span with error' do
+            expect { query }.to raise_error(Mysql2::Error)
+            expect(span).not_to have_error
+          end
+        end
       end
     end
   end