# IFairshareSchedulingPolicy

Represents a Fairshare Scheduling Policy. Instructs the scheduler to allocate ComputeEnvironment vCPUs based on Job shareIdentifiers.

The Faireshare Scheduling Policy ensures that each share gets a certain amount of vCPUs.
It does this by deciding how many Jobs of each share to schedule *relative to how many jobs of
each share are currently being executed by the ComputeEnvironment*. The weight factors associated with
each share determine the ratio of vCPUs allocated; see the readme for a more in-depth discussion of
fairshare policies.

Extends: IFairshareSchedulingPolicy
Extends: ISchedulingPolicy
Implemented by: FairshareSchedulingPolicy

- Source: [`aws-batch/lib/scheduling-policy.ts`](https://github.com/aws/aws-cdk/blob/v2.275.0/packages/aws-cdk-lib/aws-batch/lib/scheduling-policy.ts#L107)
- Type last changed: v2.96.0 · 13 Sep 2023

## Properties

- `computeReservation`: number — Used to calculate the percentage of the maximum available vCPU to reserve for share identifiers not present in the Queue.

  **Default:** no vCPU is reserved

  The percentage reserved is defined by the Scheduler as:
  `(computeReservation/100)^ActiveFairShares` where `ActiveFairShares` is the number of active fair share identifiers.

  For example, a computeReservation value of 50 indicates that AWS Batch reserves 50% of the
  maximum available vCPU if there's only one fair share identifier.
  It reserves 25% if there are two fair share identifiers.
  It reserves 12.5% if there are three fair share identifiers.

  A computeReservation value of 25 indicates that AWS Batch should reserve 25% of the
  maximum available vCPU if there's only one fair share identifier,
  6.25% if there are two fair share identifiers,
  and 1.56% if there are three fair share identifiers.

- `env`: [ResourceEnvironment](/cdk/api/v2/docs/aws-cdk-lib.interfaces.ResourceEnvironment.html) — The environment this resource belongs to.

  For resources that are created and managed in a Stack (those created by
  creating new class instances like `new Role()`, `new Bucket()`, etc.), this
  is always the same as the environment of the stack they belong to.

  For referenced resources (those obtained from referencing methods like
  `Role.fromRoleArn()`, `Bucket.fromBucketName()`, etc.), they might be
  different than the stack they were imported into.

- `node`: [Node](/cdk/api/v2/docs/constructs.Node.html) — The tree node.

- `schedulingPolicyArn`: string — The arn of this scheduling policy.

- `schedulingPolicyName`: string — The name of this scheduling policy.

- `schedulingPolicyRef`: [SchedulingPolicyReference](/cdk/api/v2/docs/aws-cdk-lib.interfaces.aws_batch.SchedulingPolicyReference.html) — A reference to a SchedulingPolicy resource.

- `shareDecay`: [Duration](/cdk/api/v2/docs/aws-cdk-lib.Duration.html) — The amount of time to use to measure the usage of each job.

  **Default:** 0: only the current job usage is considered

  The usage is used to calculate a fair share percentage for each fair share identifier currently in the Queue.
  A value of zero (0) indicates that only current usage is measured.
  The decay is linear and gives preference to newer jobs.

  The maximum supported value is 604800 seconds (1 week).

- `shares`: [Share](/cdk/api/v2/docs/aws-cdk-lib.aws_batch.Share.html)[] — The shares that this Scheduling Policy applies to.

  *Note*: It is possible to submit Jobs to the queue with Share Identifiers that
  are not recognized by the Scheduling Policy.

- `stack`: [Stack](/cdk/api/v2/docs/aws-cdk-lib.Stack.html) — The stack in which this resource is defined.

## Methods

- `applyRemovalPolicy(policy: RemovalPolicy): void` — Apply the given removal policy to this resource.

  The Removal Policy controls what happens to this resource when it stops
  being managed by CloudFormation, either because you've removed it from the
  CDK application or because you've made a change that requires the resource
  to be replaced.

  The resource can be deleted (`RemovalPolicy.DESTROY`), or left in your AWS
  account for data recovery and cleanup later (`RemovalPolicy.RETAIN`).

- `with(...mixins: IMixin[]): IConstruct` — Applies one or more mixins to this construct.

  Mixins are applied in order. The list of constructs is captured at the
  start of the call, so constructs added by a mixin will not be visited.

  **Parameters**

  - `mixins` — The mixins to apply.

  **Returns:** This construct for chaining