1 files changed, 67 insertions, 0 deletions
diff --git a/lib/gitlab/memory/reports/jemalloc_stats.rb b/lib/gitlab/memory/reports/jemalloc_stats.rb
new file mode 100644
index 00000000000..b99bec4ac3e
--- /dev/null
+++ b/lib/gitlab/memory/reports/jemalloc_stats.rb
@@ -0,0 +1,67 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Memory
+    module Reports
+      class JemallocStats
+        # On prod, Jemalloc reports sizes were ~2.5 MB:
+        # https://gitlab.com/gitlab-com/gl-infra/reliability/-/issues/15993#note_1014767214
+        # We configured 1GB emptyDir per pod:
+        # https://gitlab.com/gitlab-com/gl-infra/k8s-workloads/gitlab-com/-/merge_requests/1949
+        # The pod will be evicted when the size limit is exceeded. We never want this to happen, for availability.
+        #
+        # With the default, we have a headroom (250*2.5MB=625<1000 MB) to fit into configured emptyDir.
+        # It would allow us to keep 3+ days worth of reports for 6 workers running every 2 hours: 3*6*12=216<250
+        #
+        # The cleanup logic will be redundant after we'll implement the uploads, which would perform the cleanup.
+        DEFAULT_MAX_REPORTS_STORED = 250
+
+        def initialize(reports_path:)
+          @reports_path = reports_path
+        end
+
+        def run
+          return unless active?
+
+          Gitlab::Memory::Jemalloc.dump_stats(path: reports_path, filename_label: worker_id).tap { cleanup }
+        end
+
+        def active?
+          Feature.enabled?(:report_jemalloc_stats, type: :ops)
+        end
+
+        private
+
+        attr_reader :reports_path
+
+        def cleanup
+          reports_files_modified_order[0...-max_reports_stored].each do |f|
+            File.unlink(f) if File.exist?(f)
+          rescue Errno::ENOENT
+            # Path does not exist: Ignore. We already check `File.exist?`
+            # Rescue to be extra safe, because each worker could perform a cleanup
+          end
+        end
+
+        def reports_files_modified_order
+          pattern = File.join(reports_path, "#{Gitlab::Memory::Jemalloc::FILENAME_PREFIX}*")
+
+          Dir.glob(pattern).sort_by do |f|
+            test('M', f)
+          rescue Errno::ENOENT
+            # Path does not exist: Return any timestamp to proceed with the sort
+            Time.current
+          end
+        end
+
+        def worker_id
+          ::Prometheus::PidProvider.worker_id
+        end
+
+        def max_reports_stored
+          ENV["GITLAB_DIAGNOSTIC_REPORTS_JEMALLOC_MAX_REPORTS_STORED"] || DEFAULT_MAX_REPORTS_STORED
+        end
+      end
+    end
+  end
+end