README
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Fairness Policies
Fairness policies determine which active flow within a Priority Band is selected for the next dispatch opportunity. They manage contention between tenants or models sharing the same priority level.
This corresponds to Tier 2 of the strict 3-Tier Dispatch Hierarchy in the Flow Control system:
- Priority (Band Selection): Selects the highest-priority Band that has pending work.
- Fairness (Flow Selection): [Implemented by this package] Determines which Flow within that band gets the next dispatch opportunity.
- Ordering (Item Selection): Determines which Request from that specific flow's queue is dispatched.
Architecture: The Flyweight Pattern
Fairness policies must often maintain state (e.g., Round Robin cursors) for each Priority Band they govern. To support this efficiently without creating a new plugin instance for every Band, this package uses the Flyweight pattern:
- The Plugin Instance is a Singleton containing only immutable configuration.
- The State is created via
NewState()and stored on the Band. - The Logic (
Pickmethod) accepts the State as an argument during execution.
Available Implementations
- Round Robin (
round-robin-fairness-policy): Cycles through active flows one by one to guarantee no single flow can starve others. - Global Strict (
global-strict-fairness-policy): A greedy strategy that ignores flow boundaries and picks the absolute "best" request globally.
Conformance Testing
This directory contains a functional test suite (functional_test.go) that verifies FairnessPolicy implementations against the expected contract.
To run the conformance tests:
go test ./pkg/epp/framework/plugins/flowcontrol/fairness/...
To include a new fairness policy in these tests, add its factory to the local policies map inside TestFairnessPolicyConformance within functional_test.go.
Documentation
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Overview ¶
Package fairness provides the standard implementations of the FairnessPolicy interface.
For a detailed description of the concepts and available implementations, see the README.md file in this directory.
Source Files
Directories
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| Path | Synopsis |
|---|---|
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Package globalstrict implements a greedy fairness policy that enforces a strict global ordering across all flows within a priority band, ignoring flow boundaries.
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Package globalstrict implements a greedy fairness policy that enforces a strict global ordering across all flows within a priority band, ignoring flow boundaries. |
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Package programaware implements a flow-control fairness policy that schedules per-program queues using a swappable scoring strategy.
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Package programaware implements a flow-control fairness policy that schedules per-program queues using a swappable scoring strategy. |
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Package roundrobin implements a fairness policy that selects queues from a priority band using a round-robin strategy, cycling through active flows one by one to guarantee that no single flow can starve others.
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Package roundrobin implements a fairness policy that selects queues from a priority band using a round-robin strategy, cycling through active flows one by one to guarantee that no single flow can starve others. |