docs: add OpenSpec change for downscale improvements#253
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Adds the design artifacts for the kafka cluster downscale improvement initiative, covering two related fixes: 1. Batched broker removal - submit all brokers removed in a single manifest apply as one CC remove_broker operation instead of N separate operations, eliminating redundant partition movements. 2. Draining broker listener retention - keep brokers removed from spec in envoy/istio/contour config until CruiseControl completes draining (GracefulDownscaleSucceeded), preserving client connectivity. Artifacts: proposal, design, capability specs, and implementation tasks. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…Control completes Brokers removed from the KafkaCluster spec were immediately excluded from envoy, istio, and contour config, even while CruiseControl was still draining them. Clients lost connectivity to brokers that still held partition leaders. Root cause: ShouldIncludeBroker() returned false when brokerConfig==nil (broker not in spec). Add a fallback path: when brokerConfig is nil, check the broker's CruiseControlState in status. If the state is an active downscale (IsDownscale && !IsSucceeded) and the broker was previously bound to the requested ingressConfig, keep it in the external listener resources. Brokers stuck in CompletedWithError or Paused are also retained, allowing manual investigation while keeping client connectivity. ShouldIncludeBroker is the single gatekeeper for all external listener reconcilers (envoy, istio, contour), so no other files need changes. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
When removing multiple brokers from a KafkaCluster spec, the operator previously created one CruiseControlOperation per broker. CC can only run one operation at a time, causing data to be shuffled onto brokers that will themselves be decommissioned, far more partition movements than necessary. Collect all broker IDs in GracefulDownscaleRequired state and submit them as a single remove_broker CC operation, mirroring the existing addBrokers pattern. Because the KafkaCluster reconciler sets all removed brokers to Required via a single atomic status patch, all brokers from a single manifest apply are guaranteed to land in the same batch. Includes unit test (createCCOperation multi-broker params), integration test (exactly one CCOperation created for two simultaneous removals), e2e test scaffold, and 5-broker sample manifest. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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This was referenced Jun 22, 2026
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Adds the design artifacts for the kafka cluster downscale improvement initiative, covering two related fixes:
Batched broker removal - submit all brokers removed in a single manifest apply as one CC remove_broker operation instead of N separate operations, eliminating redundant partition movements.
Draining broker listener retention - keep brokers removed from spec in envoy/istio/contour config until CruiseControl completes draining (GracefulDownscaleSucceeded), preserving client connectivity.
Artifacts: proposal, design, capability specs, and implementation tasks.
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