Manage TiKV regions on TiDB
Manage TiKV regions on TiDB
February 11, 2023
TiDB data is split into multiple nodes and they’re called the name as a region.
In this document, I just played around to confirm the places and behaviors for regions on TiDB.
Manage TiKV regions through PD metadata
To handle PD metadata from CLI, follow this document.
At first, a port-forward to access PD pods
kubectl port-forward -n tidb-cluster svc/basic-pd 2379:2379 &>/tmp/portforward-pd.log &Then run following sub commands to check each.
These commands are one of pd-ctl, listed in this document, and to execute them, it has to add a command like tiup ctl:v6.5.0 pd -u http://127.0.0.1:2379 store:
- Show stores (TiKV nodes):
store - Confirm regions:
region - Confirm a specific region by its key:
region key 7480000000000000FF5E00000000000000F8 - Confirm the hot spots by
hot (read|write) - Confirm an abnormal region:
region check (miss-peer|extra-peer|down-peer|pending-peer)
Confirm regions on a table
To confirm regions via TiDB:
show table [table] regions;
show table [table] index [index] regions;The examples to look around regions:
mysql> show table salaries regions;
+-----------+----------------------------------------------+----------------------------------------------+-----------+-----------------+------------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+
| REGION_ID | START_KEY | END_KEY | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS | SCHEDULING_CONSTRAINTS | SCHEDULING_STATE |
+-----------+----------------------------------------------+----------------------------------------------+-----------+-----------------+------------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+
| 5161 | t_113_ | t_113_r_03800000000003112104194fb40000000000 | 5164 | 5004 | 5162, 5163, 5164 | 0 | 0 | 0 | 77 | 988924 | | |
| 5165 | t_113_r_03800000000003112104194fb40000000000 | t_113_r_0380000000000623c70419599e0000000000 | 5167 | 5003 | 5166, 5167, 5168 | 0 | 39 | 0 | 72 | 942081 | | |
| 5149 | t_113_r_0380000000000623c70419599e0000000000 | t_115_ | 5151 | 5003 | 5150, 5151, 5152 | 0 | 42 | 0 | 72 | 941966 | | |
+-----------+----------------------------------------------+----------------------------------------------+-----------+-----------------+------------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+
3 rows in set (0.04 sec)
-- Check regions for a secondary index
mysql> create index salaries_to_date on salaries(to_date);
mysql> show table salaries index salaries_to_date regions;
+-----------+--------------------------------------------------------------------+--------------------------------------------------------------------+-----------+-----------------+------------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+
| REGION_ID | START_KEY | END_KEY | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS | SCHEDULING_CONSTRAINTS | SCHEDULING_STATE |
+-----------+--------------------------------------------------------------------+--------------------------------------------------------------------+-----------+-----------------+------------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+
| 6001 | t_113_ | t_113_i_2_041934020000000000038000000000005185041933e20000000000 | 6004 | 5004 | 6002, 6003, 6004 | 0 | 39 | 0 | 25 | 328620 | | |
| 6021 | t_113_i_2_041934020000000000038000000000005185041933e20000000000 | t_113_i_2_04195b0c0000000000038000000000037e2e041957cc0000000000 | 6024 | 5004 | 6022, 6023, 6024 | 0 | 39 | 0 | 52 | 0 | | |
| 6009 | t_113_i_2_04195b0c0000000000038000000000037e2e041957cc0000000000 | t_113_i_2_04195b7400000000000380000000000652cb041958340000000000 | 6010 | 1 | 6010, 6011, 6012 | 0 | 427 | 0 | 2 | 30720 | | |
| 6017 | t_113_i_2_04195b7400000000000380000000000652cb041958340000000000 | t_113_i_2_04196c5a000000000003800000000001677d0419691a0000000000 | 6020 | 5004 | 6018, 6019, 6020 | 0 | 39 | 0 | 52 | 0 | | |
| 6013 | t_113_i_2_04196c5a000000000003800000000001677d0419691a0000000000 | t_113_i_2_047ef1020000000000038000000000007c3e04196bd80000000000 | 6015 | 5003 | 6014, 6015, 6016 | 0 | 427 | 0 | 2 | 30720 | | |
| 6005 | t_113_i_2_047ef1020000000000038000000000007c3e04196bd80000000000 | t_113_i_2_047ef102000000000003800000000007a11f04196a3a000000000000 | 6008 | 5004 | 6006, 6007, 6008 | 0 | 613 | 0 | 18 | 222607 | | |
| 5161 | t_113_i_2_047ef102000000000003800000000007a11f04196a3a000000000000 | t_113_r_03800000000003112104194fb40000000000 | 5164 | 5004 | 5162, 5163, 5164 | 0 | 517 | 0 | 76 | 985862 | | |
+-----------+--------------------------------------------------------------------+--------------------------------------------------------------------+-----------+-----------------+------------------+------------+---------------+------------+----------------------+------------------+------------------------+------------------+
7 rows in set (0.07 sec)
--- Check region peers and if it's leader
mysql> select * from information_schema.tikv_region_peers order by region_id;
+-----------+---------+----------+------------+-----------+--------+--------------+
| REGION_ID | PEER_ID | STORE_ID | IS_LEARNER | IS_LEADER | STATUS | DOWN_SECONDS |
+-----------+---------+----------+------------+-----------+--------+--------------+
| 2 | 3 | 1 | 0 | 0 | NORMAL | NULL |
| 2 | 5048 | 5003 | 0 | 1 | NORMAL | NULL |
| 2 | 5092 | 5004 | 0 | 0 | NORMAL | NULL |
| 10 | 5088 | 5004 | 0 | 0 | NORMAL | NULL |
| 10 | 11 | 1 | 0 | 1 | NORMAL | NULL |
| 10 | 5044 | 5003 | 0 | 0 | NORMAL | NULL |
| 5129 | 5132 | 5004 | 0 | 0 | NORMAL | NULL |
| 5129 | 5130 | 1 | 0 | 0 | NORMAL | NULL |
| 5129 | 5131 | 5003 | 0 | 1 | NORMAL | NULL |
| 5141 | 5143 | 5003 | 0 | 1 | NORMAL | NULL |
| 5141 | 5144 | 5004 | 0 | 0 | NORMAL | NULL |
| 5141 | 5142 | 1 | 0 | 0 | NORMAL | NULL |
...Split regions
There is a query to split by SPLIT TABLE table_name [INDEX index_name] BETWEEN (lower_value) AND (upper_value) REGIONS region_num
Add new node and distribute regions
Following this document, just adding nodes dynamically. Then regions are automatically distributed by PD.
kubectl patch -n tidb-cluster tc basic --type merge --patch '{"spec":{"tikv":{"replicas":5}}}'
kubectl get pods -wThen run tiup ctl:v6.5.0 pod -u http://127.0.0.1:2379 store a few times and see the number of region and leader counts would increase on the new node.
Confirm multiple regions
Follow
tiup ctl:v6.5.0 pd -u http://127.0.0.1:2379 config set replication.max-replicas 5On TiDB, update tidb_replica_read to follower to enable a follower read
set @@tidb_replica_read = 'follower';TODO: But still all replicas show that role name is Voter, and no replica shows a Follower.
tiup ctl:v6.5.0 pd -u http://127.0.0.1:2379 region | jq . | lessLast updated on