Feature/dynamic weight

[LikiosSedo]

Dynamic Weight Calculation for HTTPRoute BackendRefs

Resolves: #60

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Summary

Implement dynamic weight calculation for HTTPRoute backendRefs based on Application ReadyReplicas to solve multi-tenant load balancing issues.

Problem

HTTPRoute backend weights are statically configured, causing unfair traffic distribution:

• Applications with many replicas are underutilized
• Applications with few replicas are overloaded
• Poor resource efficiency in multi-tenant scenarios

Example:

Tenant A: 10 replicas → receives 33% traffic (should be 62.5%)
Tenant B: 5 replicas  → receives 33% traffic (should be 31.25%)
Tenant C: 1 replica   → receives 33% traffic (should be 6.25%)

Solution

Core Change: Calculate weight dynamically based on ReadyReplicas

Benefits:

1. Traffic distributed proportionally to application capacity
2. Automatic adjustment during scaling operations
3. Support for progressive deployments
4. Better resource utilization in multi-tenant environments

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Implementation

ArksApplication

Before:

if app.Spec.Replicas != int(app.Status.ReadyReplicas) {
    continue  // Skip if not fully Ready
}
Weight: &ep.Spec.DefaultWeight  // Static weight

After:

weight := int32(app.Status.ReadyReplicas)
if weight == 0 {
    continue  // Skip only if zero Ready
}
Weight: &weight  // Dynamic weight

ArksDisaggregatedApplication

Before:

// Require Prefill/Decode fully Ready
if app.Status.Router.ReadyReplicas > 0 &&
    app.Status.Prefill.ReadyReplicas == app.Status.Prefill.Replicas &&
    app.Status.Decode.ReadyReplicas == app.Status.Decode.Replicas {
    Weight: &ep.Spec.DefaultWeight
}

After:

// Use Router.ReadyReplicas as weight
weight := int32(app.Status.Router.ReadyReplicas)
if weight == 0 ||
   app.Status.Prefill.ReadyReplicas == 0 ||
   app.Status.Decode.ReadyReplicas == 0 {
    continue
}
Weight: &weight

Key Changes:

• ArksApplication: weight = ReadyReplicas
• ArksDisaggregatedApplication: weight = Router.ReadyReplicas
• Allow partial Ready state during scaling
• Enhanced logging with weight information

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Testing

Comprehensive testing completed in multi-tenant environment:

Test Scenario	Result
Multi-tenant load balancing (1, 10, 5 replicas)	PASS: Weights correctly match ReadyReplicas
Progressive deployment (scaling 1→10)	PASS: Weight tracks ReadyReplicas during scaling
Edge cases (scale to zero, recovery)	PASS: Correctly excluded/re-added
Performance and stability	PASS: No regressions, stable controller

Verification:

• HTTPRoute weights correctly reflect ReadyReplicas
• Traffic distributed proportionally to capacity
• Controller remains stable (no restarts, normal resource usage)
• No performance regression

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Compatibility

Backward Compatibility: Fully compatible

• No API or CRD changes
• Existing deployments benefit automatically after upgrade
• No migration required

Breaking Changes: None

Rollback: Safe rollback available if needed

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Checklist

• Changes clearly explained
• Tests pass successfully
• Code adheres to project style
• No regressions introduced
• Deployment verified in production-like environment

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