[jira] [Assigned] (KUDU-3801) Add documentation

["Gabriella Lotz (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KUDU-3801?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Gabriella Lotz reassigned KUDU-3801:
------------------------------------

    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.



--
This message was sent by Atlassian Jira
(v8.20.10#820010)