1 files changed, 46 insertions, 0 deletions
diff --git a/lib/gitlab/database/query_analyzers/gitlab_schemas_metrics.rb b/lib/gitlab/database/query_analyzers/gitlab_schemas_metrics.rb
new file mode 100644
index 00000000000..06e2b114c91
--- /dev/null
+++ b/lib/gitlab/database/query_analyzers/gitlab_schemas_metrics.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Database
+    module QueryAnalyzers
+      # The purpose of this analyzer is to observe via prometheus metrics
+      # all unique schemas observed on a given connection
+      #
+      # This effectively allows to do sample 1% or 0.01% of queries hitting
+      # system and observe if on a given connection we observe queries that
+      # are misaligned (`ci_replica` sees queries doing accessing only `gitlab_main`)
+      #
+      class GitlabSchemasMetrics < Base
+        class << self
+          def enabled?
+            ::Feature::FlipperFeature.table_exists? &&
+              Feature.enabled?(:query_analyzer_gitlab_schema_metrics)
+          end
+
+          def analyze(parsed)
+            db_config_name = ::Gitlab::Database.db_config_name(parsed.connection)
+            return unless db_config_name
+
+            gitlab_schemas = ::Gitlab::Database::GitlabSchema.table_schemas(parsed.pg.tables)
+            return if gitlab_schemas.empty?
+
+            # to reduce amount of labels sort schemas used
+            gitlab_schemas = gitlab_schemas.to_a.sort.join(",")
+
+            schemas_metrics.increment({
+              gitlab_schemas: gitlab_schemas,
+              db_config_name: db_config_name
+            })
+          end
+
+          def schemas_metrics
+            @schemas_metrics ||= ::Gitlab::Metrics.counter(
+              :gitlab_database_decomposition_gitlab_schemas_used,
+              'The number of observed schemas dependent on connection'
+            )
+          end
+        end
+      end
+    end
+  end
+end