From 6653ccc011dec86e5140a5d09ea3b2357eab6714 Mon Sep 17 00:00:00 2001
From: GitLab Bot <gitlab-bot@gitlab.com>
Date: Fri, 12 Mar 2021 16:26:10 +0000
Subject: Add latest changes from gitlab-org/gitlab@13-10-stable-ee

---
 lib/gitlab/optimistic_locking.rb | 61 ++++++++++++++++++++++++++++++++--------
 1 file changed, 50 insertions(+), 11 deletions(-)

(limited to 'lib/gitlab/optimistic_locking.rb')

diff --git a/lib/gitlab/optimistic_locking.rb b/lib/gitlab/optimistic_locking.rb
index d51d718c826..b29240985f1 100644
--- a/lib/gitlab/optimistic_locking.rb
+++ b/lib/gitlab/optimistic_locking.rb
@@ -2,22 +2,61 @@
 
 module Gitlab
   module OptimisticLocking
+    MAX_RETRIES = 100
+
     module_function
 
-    def retry_lock(subject, retries = nil, &block)
-      retries ||= 100
-      # TODO(Observability): We should be recording details of the number of retries and the duration of the total execution here
-      ActiveRecord::Base.transaction do
-        yield(subject)
-      end
-    rescue ActiveRecord::StaleObjectError
-      retries -= 1
-      raise unless retries >= 0
+    def retry_lock(subject, max_retries = MAX_RETRIES, name:, &block)
+      start_time = Gitlab::Metrics::System.monotonic_time
+      retry_attempts = 0
+
+      begin
+        ActiveRecord::Base.transaction do
+          yield(subject)
+        end
+      rescue ActiveRecord::StaleObjectError
+        raise unless retry_attempts < max_retries
+
+        subject.reset
 
-      subject.reset
-      retry
+        retry_attempts += 1
+        retry
+      ensure
+        retry_lock_histogram.observe({}, retry_attempts)
+
+        log_optimistic_lock_retries(
+          name: name,
+          retry_attempts: retry_attempts,
+          start_time: start_time)
+      end
     end
 
     alias_method :retry_optimistic_lock, :retry_lock
+
+    def log_optimistic_lock_retries(name:, retry_attempts:, start_time:)
+      return unless retry_attempts > 0
+
+      elapsed_time = Gitlab::Metrics::System.monotonic_time - start_time
+
+      retry_lock_logger.info(
+        message: "Optimistic Lock released with retries",
+        name: name,
+        retries: retry_attempts,
+        time_s: elapsed_time)
+    end
+
+    def retry_lock_logger
+      @retry_lock_logger ||= Gitlab::Services::Logger.build
+    end
+
+    def retry_lock_histogram
+      @retry_lock_histogram ||=
+        Gitlab::Metrics.histogram(
+          :gitlab_optimistic_locking_retries,
+          'Number of retry attempts to execute optimistic retry lock',
+          {},
+          [0, 1, 2, 3, 5, 10, 50]
+        )
+    end
   end
 end
-- 
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