docs: per-broker restart probes for operator rolling restarts (26.2)

[david-yu]

Documents the per-broker pre/post-restart probes that gate operator-driven rolling restarts (redpanda-operator#1547, merged 2026-06-25, ships in operator v26.2.x).

Changes

1. New section How the Redpanda Operator gates each restart under "What happens during a rolling restart" on manage:kubernetes/k-rolling-restart.adoc:
   • The operator replaces Pods itself, one broker per pass, re-evaluating against a fresh broker view each time
   • Pre-restart probe (GET /v1/broker/pre_restart_probe): the restart is delayed while it would lose acks=1-acknowledged data, make partitions unavailable, or block acks=all produce; replication-factor-1 partitions don't block (no redundancy to preserve — cross-linked to the existing RF-1 guidance in the procedure)
   • Post-restart probe (GET /v1/broker/post_restart_probe): the next restart is held until the recovering broker reports 100% of its in-sync-replica load reclaimed, because Pod readiness can pass while the broker is still replaying partition state
   • Version behavior: probes require Redpanda 25.1+; on older versions the operator falls back to the cluster-wide health check; probes run only while a restart is in progress
2. What's new: Safer rolling restarts with per-broker health probes entry under Redpanda Operator v26.2.x in get-started:release-notes/operator.adoc.

Verification

Content follows the eng PR's probe contract and was cross-checked against operator main: internal/probes/broker.go (risk-category interpretation, load_reclaimed_pc >= 100 threshold, 404 fallbacks) and internal/lifecycle/client.go (operator-managed StatefulSets use the OnDelete update strategy, so the operator's gated roll loop performs the restarts). The eng PR's EKS E2E (6 brokers, sustained rolls under load) recorded 88 post-restart deferrals and 32 pre-restart blocks with zero acks=1 loss.

Note: this PR inserts a section under the v26.2.x what's-new heading, as do open PRs #1808 and #1825 — whichever merges later needs a trivial conflict resolution (the entries just stack).

Preview pages

• Perform a Rolling Restart of Redpanda in Kubernetes (updated)
• What's New in the Redpanda Operator (updated)

🤖 Generated with Claude Code

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