fix: Use monotonic clock so postgres timeouts are unaffected by system clock changes (#141)

Author: eliotsykes

lib/with_advisory_lock/core_advisory.rb

@@ -70,8 +70,8 @@ def advisory_lock_and_yield(lock_name, lock_str, lock_stack_item, options, &)
 
     def yield_with_lock_and_timeout(lock_keys, lock_name, lock_str, lock_stack_item, shared, transaction,
                                     timeout_seconds, &)
-      give_up_at = timeout_seconds ? Time.now + timeout_seconds : nil
-      while give_up_at.nil? || Time.now < give_up_at
+      give_up_at = timeout_seconds ? Process.clock_gettime(Process::CLOCK_MONOTONIC) + timeout_seconds : nil
+      while give_up_at.nil? || Process.clock_gettime(Process::CLOCK_MONOTONIC) < give_up_at
         r = yield_with_lock(lock_keys, lock_name, lock_str, lock_stack_item, shared, transaction, 0, &)
         return r if r.lock_was_acquired?
 

test/with_advisory_lock/lock_test.rb

@@ -200,13 +200,14 @@ def setup
 
     begin
       # Attempt to acquire with a short timeout - should fail quickly
-      start_time = Time.now
-      result = model_class.with_advisory_lock(lock_name, timeout_seconds: 1) { 'success' }
-      elapsed = Time.now - start_time
+      elapsed = Benchmark.realtime do
+        result = model_class.with_advisory_lock(lock_name, timeout_seconds: 1) { 'success' }
+
+        # Should return false and complete within reasonable time (< 3 seconds)
+        # If it were using Ruby polling, it would take longer
+        assert_not result
+      end
 
-      # Should return false and complete within reasonable time (< 3 seconds)
-      # If it were using Ruby polling, it would take longer
-      assert_not result
       assert elapsed < 3.0, "Expected quick timeout, but took #{elapsed} seconds"
     ensure
       other_conn.query_value("SELECT RELEASE_LOCK(#{other_conn.quote(lock_keys.first)})")