[转帖]tidb Modify Configuration Dynamically

https://docs.pingcap.com/tidb/v6.5/dynamic-config

This document describes how to dynamically modify the cluster configuration.

You can dynamically update the configuration of components (including TiDB, TiKV, and PD) using SQL statements, without restarting the cluster components. Currently, the method of changing TiDB instance configuration is different from that of changing configuration of other components (such TiKV and PD).

Common Operations

This section describes the common operations of dynamically modifying configuration.

View instance configuration

To view the configuration of all instances in the cluster, use the show config statement. The result is as follows:

show config;

+------+-----------------+-----------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Type | Instance | Name | Value | +------+-----------------+-----------------------------------------------------------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | tidb | 127.0.0.1:4001 | advertise-address | 127.0.0.1 | | tidb | 127.0.0.1:4001 | binlog.binlog-socket | | | tidb | 127.0.0.1:4001 | binlog.enable | false | | tidb | 127.0.0.1:4001 | binlog.ignore-error | false | | tidb | 127.0.0.1:4001 | binlog.strategy | range | | tidb | 127.0.0.1:4001 | binlog.write-timeout | 15s | | tidb | 127.0.0.1:4001 | check-mb4-value-in-utf8 | true | ...

You can filter the result by fields. For example:

show config where type='tidb' show config where instance in (...) show config where name like '%log%' show config where type='tikv' and name='log.level'

Modify TiKV configuration dynamically

 

Note

• After dynamically changing TiKV configuration items, the TiKV configuration file is automatically updated. However, you also need to modify the corresponding configuration items by executing tiup edit-config; otherwise, operations such as upgrade and reload will overwrite your changes. For details of modifying configuration items, refer to Modify configuration using TiUP.
• After executing tiup edit-config, you do not need to execute tiup reload.

When using the set config statement, you can modify the configuration of a single instance or of all instances according to the instance address or the component type.

• Modify the configuration of all TiKV instances:

 

Note

It is recommended to wrap variable names in backticks.

set config tikv `split.qps-threshold`=1000;

• Modify the configuration of a single TiKV instance:

  set config "127.0.0.1:20180" `split.qps-threshold`=1000;

If the modification is successful, Query OK is returned:

Query OK, 0 rows affected (0.01 sec)

If an error occurs during the batch modification, a warning is returned:

set config tikv `log-level`='warn';

Query OK, 0 rows affected, 1 warning (0.04 sec)

show warnings;

+---------+------+---------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+---------------------------------------------------------------------------------------------------------------+ | Warning | 1105 | bad request to http://127.0.0.1:20180/config: fail to update, error: "config log-level can not be changed" | +---------+------+---------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)

The batch modification does not guarantee atomicity. The modification might succeed on some instances, while failing on others. If you modify the configuration of the entire TiKV cluster using set tikv key=val, your modification might fail on some instances. You can use show warnings to check the result.

If some modifications fail, you need to re-execute the corresponding statement or modify each failed instance. If some TiKV instances cannot be accessed due to network issues or machine failure, modify these instances after they are recovered.

If a configuration item is successfully modified, the result is persisted in the configuration file, which will prevail in the subsequent operations. The names of some configuration items might conflict with TiDB reserved words, such as limit and key. For these configuration items, use backtick ` to enclose them. For example, `raftstore.raft-log-gc-size-limit`.

The following TiKV configuration items can be modified dynamically:

Configuration item	Description
log.level	The log level.
raftstore.raft-max-inflight-msgs	The number of Raft logs to be confirmed. If this number is exceeded, the Raft state machine slows down log sending.
raftstore.raft-log-gc-tick-interval	The time interval at which the polling task of deleting Raft logs is scheduled
raftstore.raft-log-gc-threshold	The soft limit on the maximum allowable number of residual Raft logs
raftstore.raft-log-gc-count-limit	The hard limit on the allowable number of residual Raft logs
raftstore.raft-log-gc-size-limit	The hard limit on the allowable size of residual Raft logs
raftstore.raft-max-size-per-msg	The soft limit on the size of a single message packet that is allowed to be generated
raftstore.raft-entry-max-size	The hard limit on the maximum size of a single Raft log
raftstore.raft-entry-cache-life-time	The maximum remaining time allowed for the log cache in memory
raftstore.split-region-check-tick-interval	The time interval at which to check whether the Region split is needed
raftstore.region-split-check-diff	The maximum value by which the Region data is allowed to exceed before Region split
raftstore.region-compact-check-interval	The time interval at which to check whether it is necessary to manually trigger RocksDB compaction
raftstore.region-compact-check-step	The number of Regions checked at one time for each round of manual compaction
raftstore.region-compact-min-tombstones	The number of tombstones required to trigger RocksDB compaction
raftstore.region-compact-tombstones-percent	The proportion of tombstone required to trigger RocksDB compaction
raftstore.pd-heartbeat-tick-interval	The time interval at which a Region's heartbeat to PD is triggered
raftstore.pd-store-heartbeat-tick-interval	The time interval at which a store's heartbeat to PD is triggered
raftstore.snap-mgr-gc-tick-interval	The time interval at which the recycle of expired snapshot files is triggered
raftstore.snap-gc-timeout	The longest time for which a snapshot file is saved
raftstore.lock-cf-compact-interval	The time interval at which TiKV triggers a manual compaction for the Lock Column Family
raftstore.lock-cf-compact-bytes-threshold	The size at which TiKV triggers a manual compaction for the Lock Column Family
raftstore.messages-per-tick	The maximum number of messages processed per batch
raftstore.max-peer-down-duration	The longest inactive duration allowed for a peer
raftstore.max-leader-missing-duration	The longest duration allowed for a peer to be without a leader. If this value is exceeded, the peer verifies with PD whether it has been deleted.
raftstore.abnormal-leader-missing-duration	The normal duration allowed for a peer to be without a leader. If this value is exceeded, the peer is seen as abnormal and marked in metrics and logs.
raftstore.peer-stale-state-check-interval	The time interval to check whether a peer is without a leader
raftstore.consistency-check-interval	The time interval to check consistency (NOT recommended because it is not compatible with the garbage collection in TiDB)
raftstore.raft-store-max-leader-lease	The longest trusted period of a Raft leader
raftstore.merge-check-tick-interval	The time interval for merge check
raftstore.cleanup-import-sst-interval	The time interval to check expired SST files
raftstore.local-read-batch-size	The maximum number of read requests processed in one batch
raftstore.apply-yield-write-size	The maximum number of bytes that the Apply thread can write for one FSM (Finite-state Machine) in each round
raftstore.hibernate-timeout	The shortest wait duration before entering hibernation upon start. Within this duration, TiKV does not hibernate (not released).
raftstore.apply-pool-size	The number of threads in the pool that flushes data to the disk, which is the size of the Apply thread pool
raftstore.store-pool-size	The number of threads in the pool that processes Raft, which is the size of the Raftstore thread pool
raftstore.apply-max-batch-size	Raft state machines process data write requests in batches by the BatchSystem. This configuration item specifies the maximum number of Raft state machines that can execute the requests in one batch.
raftstore.store-max-batch-size	Raft state machines process requests for flushing logs into the disk in batches by the BatchSystem. This configuration item specifies the maximum number of Raft state machines that can process the requests in one batch.
readpool.unified.max-thread-count	The maximum number of threads in the thread pool that uniformly processes read requests, which is the size of the UnifyReadPool thread pool
readpool.unified.auto-adjust-pool-size	Determines whether to automatically adjust the UnifyReadPool thread pool size
coprocessor.split-region-on-table	Enables to split Region by table
coprocessor.batch-split-limit	The threshold of Region split in batches
coprocessor.region-max-size	The maximum size of a Region
coprocessor.region-split-size	The size of the newly split Region
coprocessor.region-max-keys	The maximum number of keys allowed in a Region
coprocessor.region-split-keys	The number of keys in the newly split Region
pessimistic-txn.wait-for-lock-timeout	The longest duration that a pessimistic transaction waits for the lock
pessimistic-txn.wake-up-delay-duration	The duration after which a pessimistic transaction is woken up
pessimistic-txn.pipelined	Determines whether to enable the pipelined pessimistic locking process
pessimistic-txn.in-memory	Determines whether to enable the in-memory pessimistic lock
quota.foreground-cpu-time	The soft limit on the CPU resources used by TiKV foreground to process read and write requests
quota.foreground-write-bandwidth	The soft limit on the bandwidth with which foreground transactions write data
quota.foreground-read-bandwidth	The soft limit on the bandwidth with which foreground transactions and the Coprocessor read data
quota.background-cpu-time	The soft limit on the CPU resources used by TiKV background to process read and write requests
quota.background-write-bandwidth	The soft limit on the bandwidth with which background transactions write data (not effective yet)
quota.background-read-bandwidth	The soft limit on the bandwidth with which background transactions and the Coprocessor read data (not effective yet)
quota.enable-auto-tune	Whether to enable the auto-tuning of quota. If this configuration item is enabled, TiKV dynamically adjusts the quota for the background requests based on the load of TiKV instances.
quota.max-delay-duration	The maximum time that a single read or write request is forced to wait before it is processed in the foreground
gc.ratio-threshold	The threshold at which Region GC is skipped (the number of GC versions/the number of keys)
gc.batch-keys	The number of keys processed in one batch
gc.max-write-bytes-per-sec	The maximum bytes that can be written into RocksDB per second
gc.enable-compaction-filter	Whether to enable compaction filter
gc.compaction-filter-skip-version-check	Whether to skip the cluster version check of compaction filter (not released)
{db-name}.max-total-wal-size	The maximum size of total WAL
{db-name}.max-background-jobs	The number of background threads in RocksDB
{db-name}.max-background-flushes	The maximum number of flush threads in RocksDB
{db-name}.max-open-files	The total number of files that RocksDB can open
{db-name}.compaction-readahead-size	The size of readahead during compaction
{db-name}.bytes-per-sync	The rate at which OS incrementally synchronizes files to disk while these files are being written asynchronously
{db-name}.wal-bytes-per-sync	The rate at which OS incrementally synchronizes WAL files to disk while the WAL files are being written
{db-name}.writable-file-max-buffer-size	The maximum buffer size used in WritableFileWrite
{db-name}.{cf-name}.block-cache-size	The cache size of a block
{db-name}.{cf-name}.write-buffer-size	The size of a memtable
{db-name}.{cf-name}.max-write-buffer-number	The maximum number of memtables
{db-name}.{cf-name}.max-bytes-for-level-base	The maximum number of bytes at base level (L1)
{db-name}.{cf-name}.target-file-size-base	The size of the target file at base level
{db-name}.{cf-name}.level0-file-num-compaction-trigger	The maximum number of files at L0 that trigger compaction
{db-name}.{cf-name}.level0-slowdown-writes-trigger	The maximum number of files at L0 that trigger write stall
{db-name}.{cf-name}.level0-stop-writes-trigger	The maximum number of files at L0 that completely block write
{db-name}.{cf-name}.max-compaction-bytes	The maximum number of bytes written into disk per compaction
{db-name}.{cf-name}.max-bytes-for-level-multiplier	The default amplification multiple for each layer
{db-name}.{cf-name}.disable-auto-compactions	Enables or disables automatic compaction
{db-name}.{cf-name}.soft-pending-compaction-bytes-limit	The soft limit on the pending compaction bytes
{db-name}.{cf-name}.hard-pending-compaction-bytes-limit	The hard limit on the pending compaction bytes
{db-name}.{cf-name}.titan.blob-run-mode	The mode of processing blob files
server.grpc-memory-pool-quota	Limits the memory size that can be used by gRPC
server.max-grpc-send-msg-len	Sets the maximum length of a gRPC message that can be sent
server.snap-max-write-bytes-per-sec	Sets the maximum allowable disk bandwidth when processing snapshots
server.concurrent-send-snap-limit	Sets the maximum number of snapshots sent at the same time
server.concurrent-recv-snap-limit	Sets the maximum number of snapshots received at the same time
server.raft-msg-max-batch-size	Sets the maximum number of Raft messages that are contained in a single gRPC message
server.simplify-metrics	Controls whether to simplify the sampling monitoring metrics
storage.block-cache.capacity	The size of shared block cache (supported since v4.0.3)
storage.scheduler-worker-pool-size	The number of threads in the Scheduler thread pool
backup.num-threads	The number of backup threads (supported since v4.0.3)
split.qps-threshold	The threshold to execute load-base-split on a Region. If the QPS of read requests for a Region exceeds qps-threshold for 10 consecutive seconds, this Region should be split.
split.byte-threshold	The threshold to execute load-base-split on a Region. If the traffic of read requests for a Region exceeds the byte-threshold for 10 consecutive seconds, this Region should be split.
split.region-cpu-overload-threshold-ratio	The threshold to execute load-base-split on a Region. If the CPU usage in the Unified Read Pool for a Region exceeds the region-cpu-overload-threshold-ratio for 10 consecutive seconds, this Region should be split. (supported since v6.2.0)
split.split-balance-score	The parameter of load-base-split, which ensures the load of the two split Regions is as balanced as possible. The smaller the value is, the more balanced the load is. But setting it too small might cause split failure.
split.split-contained-score	The parameter of load-base-split. The smaller the value, the fewer cross-Region visits after Region split.
cdc.min-ts-interval	The time interval at which Resolved TS is forwarded
cdc.old-value-cache-memory-quota	The upper limit of memory occupied by the TiCDC Old Value entries
cdc.sink-memory-quota	The upper limit of memory occupied by TiCDC data change events
cdc.incremental-scan-speed-limit	The upper limit on the speed of incremental scanning for historical data
cdc.incremental-scan-concurrency	The maximum number of concurrent incremental scanning tasks for historical data

In the table above, parameters with the {db-name} or {db-name}.{cf-name} prefix are configurations related to RocksDB. The optional values of db-name are rocksdb and raftdb.

• When db-name is rocksdb, the optional values of cf-name are defaultcf, writecf, lockcf, and raftcf.
• When db-name is raftdb, the value of cf-name can be defaultcf.

For detailed parameter description, refer to TiKV Configuration File.

Modify PD configuration dynamically

Currently, PD does not support the separate configuration for each instance. All PD instances share the same configuration.

You can modify the PD configurations using the following statement:

set config pd `log.level`='info';

If the modification is successful, Query OK is returned:

Query OK, 0 rows affected (0.01 sec)

If a configuration item is successfully modified, the result is persisted in etcd instead of in the configuration file; the configuration in etcd will prevail in the subsequent operations. The names of some configuration items might conflict with TiDB reserved words. For these configuration items, use backtick ` to enclose them. For example, `schedule.leader-schedule-limit`.

The following PD configuration items can be modified dynamically:

Configuration item	Description
log.level	The log level
cluster-version	The cluster version
schedule.max-merge-region-size	Controls the size limit of Region Merge (in MiB)
schedule.max-merge-region-keys	Specifies the maximum numbers of the Region Merge keys
schedule.patrol-region-interval	Determines the frequency at which replicaChecker checks the health state of a Region
schedule.split-merge-interval	Determines the time interval of performing split and merge operations on the same Region
schedule.max-snapshot-count	Determines the maximum number of snapshots that a single store can send or receive at the same time
schedule.max-pending-peer-count	Determines the maximum number of pending peers in a single store
schedule.max-store-down-time	The downtime after which PD judges that the disconnected store cannot be recovered
schedule.leader-schedule-policy	Determines the policy of Leader scheduling
schedule.leader-schedule-limit	The number of Leader scheduling tasks performed at the same time
schedule.region-schedule-limit	The number of Region scheduling tasks performed at the same time
schedule.replica-schedule-limit	The number of Replica scheduling tasks performed at the same time
schedule.merge-schedule-limit	The number of the Region Merge scheduling tasks performed at the same time
schedule.hot-region-schedule-limit	The number of hot Region scheduling tasks performed at the same time
schedule.hot-region-cache-hits-threshold	Determines the threshold at which a Region is considered a hot spot
schedule.high-space-ratio	The threshold ratio below which the capacity of the store is sufficient
schedule.low-space-ratio	The threshold ratio above which the capacity of the store is insufficient
schedule.tolerant-size-ratio	Controls the balance buffer size
schedule.enable-remove-down-replica	Determines whether to enable the feature that automatically removes DownReplica
schedule.enable-replace-offline-replica	Determines whether to enable the feature that migrates OfflineReplica
schedule.enable-make-up-replica	Determines whether to enable the feature that automatically supplements replicas
schedule.enable-remove-extra-replica	Determines whether to enable the feature that removes extra replicas
schedule.enable-location-replacement	Determines whether to enable isolation level check
schedule.enable-cross-table-merge	Determines whether to enable cross-table merge
schedule.enable-one-way-merge	Enables one-way merge, which only allows merging with the next adjacent Region
replication.max-replicas	Sets the maximum number of replicas
replication.location-labels	The topology information of a TiKV cluster
replication.enable-placement-rules	Enables Placement Rules
replication.strictly-match-label	Enables the label check
pd-server.use-region-storage	Enables independent Region storage
pd-server.max-gap-reset-ts	Sets the maximum interval of resetting timestamp (BR)
pd-server.key-type	Sets the cluster key type
pd-server.metric-storage	Sets the storage address of the cluster metrics
pd-server.dashboard-address	Sets the dashboard address
replication-mode.replication-mode	Sets the backup mode

For detailed parameter description, refer to PD Configuration File.

Modify TiDB configuration dynamically

Currently, the method of changing TiDB configuration is different from that of changing TiKV and PD configurations. You can modify TiDB configuration by using system variables.

The following example shows how to dynamically modify slow-threshold by using the tidb_slow_log_threshold variable.

The default value of slow-threshold is 300 ms. You can set it to 200 ms by using tidb_slow_log_threshold.

set tidb_slow_log_threshold = 200;

Query OK, 0 rows affected (0.00 sec)

select @@tidb_slow_log_threshold;

+---------------------------+ | @@tidb_slow_log_threshold | +---------------------------+ | 200 | +---------------------------+ 1 row in set (0.00 sec)

The following TiDB configuration items can be modified dynamically:

Configuration item	SQL variable
instance.tidb_enable_slow_log	tidb_enable_slow_log
instance.tidb_slow_log_threshold	tidb_slow_log_threshold
instance.tidb_expensive_query_time_threshold	tidb_expensive_query_time_threshold

Modify TiFlash configuration dynamically

Currently, you can modify the TiFlash configuration max_threads by using the system variable tidb_max_tiflash_threads, which specifies the maximum concurrency for TiFlash to execute a request.

The default value of tidb_max_tiflash_threads is -1, indicating that this system variable is invalid and depends on the setting of the TiFlash configuration file. You can set max_threads to 10 by using tidb_max_tiflash_threads:

set tidb_max_tiflash_threads = 10;

Query OK, 0 rows affected (0.00 sec)

select @@tidb_max_tiflash_threads;

+----------------------------+ | @@tidb_max_tiflash_threads | +----------------------------+ | 10 | +----------------------------+ 1 row in set (0.00 sec)

Modify Configuration Dynamicallywas last updated 2023/7/14 14:05:14: *: modify some deprecated configuration items (#14219) (#14230)