Serialize throttle limits with expiration expressed as a duration to avoid clock differences.

fdbclient/TagThrottle.h

@@ -85,7 +85,7 @@ public:
 	}
 
 //private:
-	Arena arena; // TODO: where to hold this memory?
+	Arena arena;
 	std::set<TransactionTagRef> tags;
 	size_t bytes;
 };
@@ -125,7 +125,10 @@ struct dynamic_size_traits<TagSet> : std::true_type {
 			t.bytes += tag.size();
 		}
 
-		t.arena = context.arena(); // TODO: this arena could be big
+		// Deserialized tag sets share the arena with the request that contained them
+		// For this reason, persisting a TagSet that shares memory with other request
+		// members should be done with caution.
+		t.arena = context.arena();
 	}
 };
 

fdbserver/RatekeeperInterface.h

@@ -61,7 +61,17 @@ struct ClientTagThrottleLimits {
 
 	template <class Archive>
 	void serialize(Archive& ar) {
-		serializer(ar, tpsRate, expiration);
+		// Convert expiration time to a duration to avoid clock differences
+		double duration = 0;
+		if(!ar.isDeserializing) {
+			duration = expiration - now();
+		}
+
+		serializer(ar, tpsRate, duration);
+
+		if(ar.isDeserializing) {
+			expiration = now() + duration;
+		}
 	}
 };