[MESOS-2279] Future callbacks should be cleared once the future has transitioned.

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.21.0, 0.21.1
• Fix Version/s: 0.22.0
• Sprint: Twitter Mesos Q1 Sprint 1
• Story Points: 2
• Assignee: Vinod Kone
• Reporter: Jie Yu
• Created: 27/Jan/15 21:38
• Updated: 28/Jan/15 22:27
• Resolved: 28/Jan/15 22:27

Description

For example, when a future has transitioned into READY state, all onDiscard callbacks should be cleared to avoid potential cyclic dependency and memory leak. For instance:

Promise<Nothing> promise;
Future<Nothing> f = promise.future();
f.onDiscard(lambda::bind(&SomeFunc, f));
promise.set(Nothing());

The above code has a cyclic dependency because f.data has a reference to the future inside an std::function which has a reference to f.data.