From 7a2b2e02bf363dd763f9c0a736f067c59dd9f24b Mon Sep 17 00:00:00 2001
From: Ian Baum <ibaum@gitlab.com>
Date: Fri, 12 Dec 2025 16:05:09 -0600
Subject: [PATCH] POC for tracking oldest unsynced object on a secondary

---
 ee/app/models/concerns/geo/replicable_registry.rb | 7 +++++++
 ee/app/models/geo_node_status.rb                  | 3 ++-
 ee/lib/gitlab/geo/replicator.rb                   | 4 ++++
 3 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/ee/app/models/concerns/geo/replicable_registry.rb b/ee/app/models/concerns/geo/replicable_registry.rb
index ddb7eaeacb0b41..df2557022858df 100644
--- a/ee/app/models/concerns/geo/replicable_registry.rb
+++ b/ee/app/models/concerns/geo/replicable_registry.rb
@@ -19,6 +19,12 @@ def state_value(state_string)
         STATE_VALUES[state_string]
       end
 
+      def unsynced_objects
+        # rubocop:disable Database/AvoidUsingPluckWithoutLimit -- To be fixed before merge
+        model_class.find(unsynced.pluck(model_foreign_key)).minimum(:updated_at)
+        # rubocop:enable Database/AvoidUsingPluckWithoutLimit
+      end
+
       def for_model_record_id(id)
         find_or_initialize_by(model_foreign_key => id)
       end
@@ -81,6 +87,7 @@ def replicator_class
       scope :retry_due, -> { where(arel_table[:retry_at].eq(nil).or(arel_table[:retry_at].lt(Time.current))) }
       scope :synced, -> { with_state(:synced) }
       scope :sync_timed_out, -> { with_state(:started).where(last_synced_at: ...replicator_class.sync_timeout.ago) }
+      scope :unsynced, -> { without_state(:synced) }
 
       state_machine :state, initial: :pending do
         state :pending, value: STATE_VALUES[:pending]
diff --git a/ee/app/models/geo_node_status.rb b/ee/app/models/geo_node_status.rb
index 530a07f9d9a951..7b4fa8a1c53deb 100644
--- a/ee/app/models/geo_node_status.rb
+++ b/ee/app/models/geo_node_status.rb
@@ -36,7 +36,8 @@ def self.status_fields_for(replicable_class)
       "#{replicable_class.replicable_name_plural}_registry_count": "Number of #{replicable_class.replicable_title_plural} synced to sync on secondary",
       "#{replicable_class.replicable_name_plural}_verification_total_count": "Number of #{replicable_class.replicable_title_plural} available to verify on secondary",
       "#{replicable_class.replicable_name_plural}_verified_count": "Number of #{replicable_class.replicable_title_plural} verified on the secondary",
-      "#{replicable_class.replicable_name_plural}_verification_failed_count": "Number of #{replicable_class.replicable_title_plural} failed to verify on secondary"
+      "#{replicable_class.replicable_name_plural}_verification_failed_count": "Number of #{replicable_class.replicable_title_plural} failed to verify on secondary",
+      "#{replicable_class.replicable_name_plural}_oldest_unsynced_time": "Timestamp of the oldest out of sync #{replicable_class.replicable_title_plural} on secondary"
     }
   end
 
diff --git a/ee/lib/gitlab/geo/replicator.rb b/ee/lib/gitlab/geo/replicator.rb
index 1a83864f4194eb..d02f8ae8be6405 100644
--- a/ee/lib/gitlab/geo/replicator.rb
+++ b/ee/lib/gitlab/geo/replicator.rb
@@ -175,6 +175,10 @@ def self.replication_enabled?
         Feature.enabled?(replication_enabled_feature_key, type: :ops)
       end
 
+      def self.oldest_unsynced
+        registry_class.with_state(:synced)
+      end
+
       # @example Given `Geo::PackageFileRegistryFinder`, this returns
       #   `::Geo::PackageFileReplicator`
       # @example Given `Resolver::Geo::PackageFileRegistriesResolver`, this
-- 
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