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https://issues.apache.org/jira/browse/KUDU-3801?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gabriella Lotz reassigned KUDU-3801:
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Assignee: Gabriella Lotz
> Add documentation
> -----------------
>
> Key: KUDU-3801
> URL: https://issues.apache.org/jira/browse/KUDU-3801
> Project: Kudu
> Issue Type: Sub-task
> Reporter: Gabriella Lotz
> Assignee: Gabriella Lotz
> Priority: Major
>
> The auto-rebalancer and auto-leader-rebalancer have been in the tree behind
> experimental flags for a while, but there's no user-facing documentation.
> docs/administration.adoc only covers the CLI kudu cluster rebalance tool, and
> docs/background_tasks.adoc doesn't mention either task. The only references I
> could find in docs/ are stale entries under prior_release_notes.adoc.
> Add a new section, under docs/background_tasks.adoc since these are master
> background tasks, covering:
> - What each task does and how they relate to each other, and to the CLI kudu
> cluster rebalance tool already documented in administration.adoc.
> - Prerequisites: --raft_prepare_replacement_before_eviction=true (3-4-3) is
> required for auto_rebalancing_enabled and enforced by the group validator at
> catalog_manager.cc:570. Whether it's needed for
> auto_leader_rebalancing_enabled is being decided; reflect the outcome here.
> - Operator-visible flags with recommended values and when to change them:
> auto_rebalancing_interval_seconds, auto_rebalancing_max_moves_per_server,
> auto_rebalancing_load_imbalance_threshold,
> auto_rebalancing_prefer_follower_replica_moves,
> auto_rebalancing_enable_range_rebalancing,
> auto_leader_rebalancing_interval_seconds,
> leader_rebalancing_max_moves_per_round,
> leader_rebalancing_ignore_soft_deleted_tables.
> - The metrics that were added: auto_rebalancer_leader_moves_scheduled,
> auto_rebalancer_follower_moves_scheduled, auto_rebalancer_rounds_completed,
> the four counters added under KUDU-3791, and the leader-skew gauge added
> under the related sub-task.
> - Behavior with tservers in maintenance mode: destinations in
> MAINTENANCE_MODE are skipped, and sources shed replicas/leaders.
> - Interaction with the CLI rebalancer: they share the same replica-move
> machinery, so running both at once isn't recommended.
> Also add a release-notes entry in docs/release_notes.adoc announcing that the
> two flags are no longer experimental, with a pointer to the new section.
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