1 files changed, 103 insertions, 0 deletions
diff --git a/lib/gitlab/metrics/subscribers/ldap.rb b/lib/gitlab/metrics/subscribers/ldap.rb
new file mode 100644
index 00000000000..9cac5f41090
--- /dev/null
+++ b/lib/gitlab/metrics/subscribers/ldap.rb
@@ -0,0 +1,103 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Metrics
+    module Subscribers
+      class Ldap < ActiveSupport::Subscriber
+        # This namespace is configured in the Net::LDAP library, and appears
+        # at the end of the event key, e.g. `open.net_ldap`
+        attach_to :net_ldap
+
+        COUNTER = :net_ldap_count
+        DURATION = :net_ldap_duration_s
+
+        # Assembled from methods that are instrumented inside Net::LDAP
+        OBSERVABLE_EVENTS = %i[
+          open
+          bind
+          add
+          modify
+          modify_password
+          rename
+          delete
+          search
+        ].freeze
+
+        class << self
+          # @return [Integer] the total number of LDAP requests
+          def count
+            Gitlab::SafeRequestStore[COUNTER].to_i
+          end
+
+          # @return [Float] the total duration spent on LDAP requests
+          def duration
+            Gitlab::SafeRequestStore[DURATION].to_f
+          end
+
+          # Used in Gitlab::InstrumentationHelper to merge the LDAP stats
+          # into the log output
+          #
+          # @return [Hash<Integer, Float>] a hash of the stored statistics
+          def payload
+            {
+              net_ldap_count: count,
+              net_ldap_duration_s: duration
+            }
+          end
+        end
+
+        # Called when an event is triggered in ActiveSupport::Notifications
+        #
+        # This method is aliased to the various events triggered by the
+        # Net::LDAP library, as the method will be called by those names
+        # when triggered.
+        #
+        # It stores statistics in the request for output to logs, and also
+        # resubmits the event data into Prometheus for monitoring purposes.
+        def observe_event(event)
+          add_to_request_store(event)
+          expose_metrics(event)
+        end
+
+        OBSERVABLE_EVENTS.each do |event|
+          alias_method event, :observe_event
+        end
+
+        private
+
+        def current_transaction
+          ::Gitlab::Metrics::WebTransaction.current || ::Gitlab::Metrics::BackgroundTransaction.current
+        end
+
+        # Track these events as statistics for the current requests, for logging purposes
+        def add_to_request_store(event)
+          return unless Gitlab::SafeRequestStore.active?
+
+          Gitlab::SafeRequestStore[COUNTER] = Gitlab::SafeRequestStore[COUNTER].to_i + 1
+          Gitlab::SafeRequestStore[DURATION] = Gitlab::SafeRequestStore[DURATION].to_f + event.duration.to_f
+        end
+
+        # Converts the observed events into Prometheus metrics
+        def expose_metrics(event)
+          return unless current_transaction
+
+          # event.name will be, for example, `search.net_ldap`
+          # and so we only want the first part, which is the
+          # true name of the event
+          labels = { name: event.name.split(".").first }
+
+          current_transaction.increment(:gitlab_net_ldap_total, 1, labels) do
+            docstring 'Net::LDAP calls'
+            label_keys labels.keys
+          end
+
+          current_transaction.observe(:gitlab_net_ldap_duration_seconds, event.duration, labels) do
+            docstring 'Net::LDAP time'
+            buckets [0.001, 0.01, 0.1, 1.0, 2.0, 5.0]
+            label_keys labels.keys
+          end
+        end
+      end
+    end
+  end
+end