1 files changed, 68 insertions, 0 deletions
diff --git a/lib/gitlab/memory/watchdog/event_reporter.rb b/lib/gitlab/memory/watchdog/event_reporter.rb
new file mode 100644
index 00000000000..c37426cb660
--- /dev/null
+++ b/lib/gitlab/memory/watchdog/event_reporter.rb
@@ -0,0 +1,68 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Memory
+    class Watchdog
+      class EventReporter
+        include ::Gitlab::Utils::StrongMemoize
+
+        attr_reader :logger
+
+        def initialize(logger: Gitlab::AppLogger)
+          @logger = logger
+          init_prometheus_metrics
+        end
+
+        def started(labels = {})
+          logger.info(message: 'started', **log_labels(labels))
+        end
+
+        def stopped(labels = {})
+          logger.info(message: 'stopped', **log_labels(labels))
+        end
+
+        def threshold_violated(monitor_name)
+          @counter_violations.increment(reason: monitor_name)
+        end
+
+        def strikes_exceeded(monitor_name, labels = {})
+          logger.warn(log_labels(labels))
+
+          @counter_violations_handled.increment(reason: monitor_name)
+        end
+
+        private
+
+        def log_labels(extra = {})
+          extra.merge(
+            pid: $$,
+            worker_id: worker_id,
+            memwd_rss_bytes: process_rss_bytes
+          )
+        end
+
+        def process_rss_bytes
+          Gitlab::Metrics::System.memory_usage_rss[:total]
+        end
+
+        def worker_id
+          ::Prometheus::PidProvider.worker_id
+        end
+
+        def init_prometheus_metrics
+          default_labels = { pid: worker_id }
+          @counter_violations = Gitlab::Metrics.counter(
+            :gitlab_memwd_violations_total,
+            'Total number of times a Ruby process violated a memory threshold',
+            default_labels
+          )
+          @counter_violations_handled = Gitlab::Metrics.counter(
+            :gitlab_memwd_violations_handled_total,
+            'Total number of times Ruby process memory violations were handled',
+            default_labels
+          )
+        end
+      end
+    end
+  end
+end