qslib/

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This source tree implements the QuotaScheduler algorithm.

The algorithm is similar to the Token Bucket algorithm.

A number of accounts are defined.
Each account has a quota recharge rate, defined over multiple priority levels.
Tasks belong to a particular account, and are prioritized based on the account's balance (i.e. they are given a priority corresponding to the best priority with positive quota for that account).
If the scheduler is configured with preemption enabled, tasks of higher priority may preempt lower-priority ones (and reimburse spent quota from the preempter's account).

In addition to Token Bucket, QuotaScheduler supports features directly related to the ChromeOS Test Lab's needs. In particular:

Tasks are preferentially assigned to workers that already have matching "provisionable labels" (i.e. installable dependencies).
Accounts can specify a maximum parallelism, beyond which tasks will not run concurrently.

Code layout:

profiler Performance profiling tool and simulator for quotascheduler algorithm.
protos Internal proto definitions, for serializing scheduler state.
reconciler Caching/queueing logic between swarming (which makes task- or worker- bound calls to this library) and scheduler logic (which uses a global scheduling pass on each scheduling run).
scheduler Core QuotaScheduler algorithm.
tutils Convenience library to casting proto timestamps.

Path	Synopsis
profiler Package profiler provides entity size and CPU usage profiling for quotascheduler entities.	Package profiler provides entity size and CPU usage profiling for quotascheduler entities.
protos
metrics Package metrics defines types used for structured logs and metrics of the quotascheduler behavior.	Package metrics defines types used for structured logs and metrics of the quotascheduler behavior.
reconciler Package reconciler provides a wrapper around a global state scheduler to be used by a per-worker pulling dispatcher.	Package reconciler provides a wrapper around a global state scheduler to be used by a per-worker pulling dispatcher.
scheduler Package scheduler provides Scheduler, which is an implementation of the quotascheduler algorithm.	Package scheduler provides Scheduler, which is an implementation of the quotascheduler algorithm.
tutils Package tutils provides convenience functions to convert between proto representations and time.Time / time.Duration representations of times or durations.	Package tutils provides convenience functions to convert between proto representations and time.Time / time.Duration representations of times or durations.