[MESOS-9277] UNRESERVE scheduler call be dropped if it loses the race with TEARDOWN.

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.5.1, 1.6.1, 1.7.0
• Component/s: scheduler api
• Labels: foundations mesosphere v1_api
• Assignee: Unassigned
• Reporter: Alex R
• Created: 28/Sep/18 13:08
• Updated: 17/Apr/19 19:09
• Resolved: 17/Apr/19 19:09

Description

A typical use pattern for a framework scheduler is to remove its reservations before tearing itself down. However, it is racy: UNRESERVE is a multi-stage action which aborts if the framework is removed in-between.

Solution 1
Let schedulers use operation feedback and expect them to wait for an ack for UNRESERVE before they send TEARDOWN. Kind of science fiction with a timeline of O(months) and still possibilities for the race if a scheduler does not comply.

Solution 2
Serialize calls for schedulers. For example, we can chain handlers here onto per-Master::Framework process::Sequence. For that however, handlers must provide futures indicating when the processing of the call is finished, note that most handlers here return void.