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Adjust the Drydock allocator to limit each pending lease to one allocating…

Description

Adjust the Drydock allocator to limit each pending lease to one allocating resource

Summary:
Ref T13677. Currently, one lease may cause multiple resources to allocate simultaneously if it starts allocating one, then wakes up from a yield later on and still sees no available resources.

This is never desired -- or, at least, produces desirable behavior only entirely by accident. Normally, it causes an excess of resources to allocate.

This is not a catastrophic problem: the extra resources usually get used sooner or later or cleaned up; and the total amount of badness is limited by overall resource allocation limits.

However, this behavior is also suppressed by an artificial "25% of current pool size" growth limit throttle which I intend to remove. Removing this throttle without fixing the allocator behavior could make this "too many resources" problem worse.

Change the allocator so that a lease that has started allocating a resource won't allocate another resource until the first resource leaves the "pending" state.

This also fixes some general oddness with the allocator and attempts to simplify the structure.

Test Plan:

  • Ran 8 taskmasters.
  • Destroyed all resources and leases.
  • Leased 4 working copies.
    • Saw exactly 4 resources build and lease, all simultaneously.
  • Destroyed all resources and leases.
  • Leased 32 working copies.
    • Saw exactly 32 resources build and lease, approximately 8 at a time (limited by taskmasters).
  • Destroyed all leases (but not resources).
  • Leased 32 working copies, saw them satisfied by existing resources.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13677

Differential Revision: https://secure.phabricator.com/D21807

Details

Provenance
epriestley <git@epriestley.com>Authored on May 9 2022, 17:03
aviveyPushed on Tue, Jul 26, 15:02
aviveyPushed on Tue, Jul 26, 15:01
Differential Revision
D25040: merge phab/master -> phorge/master
Parents
rP13a37282bcb3: Formalize some more Drydock conditions and bookkeeping
Branches
Unknown
Tags
Unknown
Tasks
T15094: Catch up the master branch to upstream