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https://issues.apache.org/jira/browse/KUDU-3731?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18076068#comment-18076068
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Gabriella Lotz commented on KUDU-3731:
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h2. Replica Rebalancer: New/Returning Tablet Server
h3. Setup:
4-tserver cluster, RF=3 table with 8 hash-bucket tablets (24 replicas, 6 per
tserver). auto_rebalancing_interval_seconds=30.
h3. Adding a new tserver:
A 4th tserver was added to a previously 3-tserver cluster. It joined with 0
replicas. Within one rebalancer interval the master began scheduling moves. The
cluster converged to 6-6-6-6 within a single 30s round. The table remained
HEALTHY throughout.
h3. Kill and recovery:
One tserver was killed. Replicas redistributed to the three survivors (8-8-8).
The tserver was then restarted. It re-registered and its existing replicas
rejoined their Raft groups. The rebalancer converged back to 6-6-6-6 over two
rounds (~60s). The table remained HEALTHY throughout. No under-replicated
tablets at any point during recovery.
> Long-running smoke test
> -----------------------
>
> Key: KUDU-3731
> URL: https://issues.apache.org/jira/browse/KUDU-3731
> Project: Kudu
> Issue Type: Sub-task
> Reporter: Gabriella Lotz
> Assignee: Gabriella Lotz
> Priority: Major
>
> h4. Step 0: Start a cluster with 1 master and 3 tablet servers.
> h4. Step 1: Set the following flags.
> --auto_rebalancing_enabled=true
> --auto_rebalancing_interval_seconds=60
> --auto_leader_rebalancing_enabled=true
> h4. Step 2: Create the following tables.
> {code:java}
> kudu table create <master> '{
> "table_name": "user_events",
> "schema": {
> "columns": [
> {"column_name": "user_id", "column_type": "STRING", "is_nullable":
> false},
> {"column_name": "event_id", "column_type": "INT64", "is_nullable":
> false},
> {"column_name": "data", "column_type": "STRING", "is_nullable":
> true}
> ],
> "key_column_names": ["user_id", "event_id"]
> },
> "partition": {
> "hash_partitions": [{"columns": ["user_id", "event_id"], "num_buckets":
> 8}]
> },
> "num_replicas": 3
> }'
> kudu table create <master> '{
> "table_name": "time_series_table",
> "schema": {
> "columns": [
> {"column_name": "ts", "column_type": "UNIXTIME_MICROS",
> "is_nullable": false},
> {"column_name": "sensor_id", "column_type": "STRING",
> "is_nullable": false},
> {"column_name": "value", "column_type": "DOUBLE",
> "is_nullable": true}
> ],
> "key_column_names": ["ts", "sensor_id"]
> },
> "partition": {
> "range_partition": {
> "columns": ["ts"],
> "range_bounds": [
> {"upper_bound": {"bound_type": "exclusive", "bound_values":
> ["1704067200000000"]}},
> {
> "lower_bound": {"bound_type": "inclusive", "bound_values":
> ["1704067200000000"]},
> "upper_bound": {"bound_type": "exclusive", "bound_values":
> ["1735689600000000"]}
> },
> {"lower_bound": {"bound_type": "inclusive", "bound_values":
> ["1735689600000000"]}}
> ]
> }
> },
> "num_replicas": 3
> }' {code}
> h4. Step 3: Start loadgen in tmux
> tmux new -s smoke
> Inside tmux:
> while true; do
> kudu perf loadgen <master> \
> --table_name=user_events \
> --num_threads=4 \
> --num_rows_per_thread=500000 \
> --flush_per_n_rows=1000 \
> --run_cleanup # cleanup so that disk doesn't fill up
> sleep 10
> done
> h4. Step 4: Monitor findings for 2 weeks. (start 2026.03.13.)
> # Is the cluster healthy?
> kudu cluster ksck <master>
> # Check whether auto-rebalancer is running.
> grep -i rebalanc /var/log/kudu/kudu-master.INFO | tail -20
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