Background threads of OceanBase Database|V4.3.0|OceanBase Database|docs|OceanBase Documentations

Thread	Module	Thread quantity	Purpose
TsMgr	Trx	1	Refreshes the local GTS cache.
WeakReadSvr	Trx	1	Calculates the local server-level read timestamp of the standby IDC.
HAGtsSource	Trx	1	Refreshes ha_gts. The refresh frequency is determined by the `gts_refresh_interval` parameter.
GCPartAdpt	Trx	1	Regularly checks the `all_tenant_gc_partition_info` table to obtain the garbage collection (GC) information of partitions. The thread helps facilitate the GC and two-phase commit of transactions.
PartWorker	Trx	1	Traverses all partitions on the local OBServer node and performs the following operations: Tries to write checkpoint logs at the transaction layer every 50 ms. Calculates the snapshot points to be migrated every 15s. Drives all active transactions in the current partition every 10s and checks the status of the scheduler. The thread helps clear the transaction context. Checks the replica table status of the current partition every 10s. Refreshes the clogs cached in the current partition every 10s.
LockWaitMgr	Trx	1	Wakes up the threads in the wait lock queue in hotspot row scenarios, such as statement timeout and session kill.
ClogAdapter	Trx	8	Asynchronously commits clogs at the transaction layer.
ObTransService	Trx	6	Performs the following operations: Processes error messages during the transaction commit. Retries a failed statement rollback. Wakes up the subsequent transactions in an early lock release scenario.
GCCollector	Storage	1	Regularly checks whether GC operation can be performed on all partitions on the local OBServer nodes. If yes, triggers a GC operation.
RebuildSche	Storage	1	Regularly drives partition tasks that need to be rebuilt.
PurgeWorker	Storage	1	Deletes MemTable labels in the background.
DAG	Storage	16	The worker thread of dag, which is used to run tasks such as the minor compactions, major compactions, and migration of partitions.
DagScheduler	Storage	1	The scheduling thread of dag.
STableChecksumUp	Storage	1	Batch commits SSTable checksum tasks.
PartitionScheduler	Storage	2	Schedules minor compaction and major compaction tasks.
MemstoreGC	Storage	1	Recycles the frozen MemStore after a warm-up for minor compactions.
ObStoreFile	Storage	1	Checks for bad macroblocks and recycles macroblocks.
PartSerCb	Storage	40	Schedules 20 threads to handle the switchover of a partition leader.
ObPartitionSplit Worker	Storage	1	Splits a partition in the background.
FreezeTimer	Storage	1	Checks the MemStore memory and triggers a freezing task.
RebuildTask	Storage	1	Schedules the D replica to pull data.
IndexSche	Storage	1	Schedules the index creation task.
FreInfoReload	Storage	1	Synchronizes major freeze information in internal tables.
TableMgrGC	Storage	1	Recycles MemTable to release memory.
BackupInfoUpdate	Storage	1	Regularly refreshes backup data.
LogDiskMon	Storage	1	Detects the multiple disks of the system.
KVCacheWash	Storage	1	Cleans the memory of KVCache. The detection interval is determined by the `_cache_wash_interval` parameter. Default value: `200ms`. Value range: [1ms,1m].
KVCacheRep	Storage	1	Manages memory fragments of the cache to recycle memory. The detection interval is determined by the `_cache_wash_interval` parameter. Default value: `200ms`. Value range: [1ms,1m].
RSMonitor	RS	1	Monitors the status of the current RootService.
CacheCalculator	RS	1	Reserves memory for location_cache and schema_cache.
ObDailyMergeScheduler	RS	1	Schedules major compaction tasks.
ObEmptyServerChecker	RS	1	Detects whether an OBServer node has replicas.
ObFetchPrimaryDDLOperator	RS	1	Synchronizes the logic of the standby database to the schema of the sys tenant of the primary database.
ObFreezeInfoUpdater	RS	1	Speeds up the progress of freeze and manages the snapshot recovery points.
ObGlobalIndexBuilder	RS	1	Schedules the creation of global indexes.
ObGlobalMaxDecidedTransVersionMgr	RS	1	Collects the statistics of the versions of global maximum transactions.
ObLeaderCoordinator	RS	1	Manages the distribution of leader replicas in a cluster.
ObLogArchiveScheduler	RS	1	Archives the log files.
ObMajorFreezeLauncher	RS	1	Launches scheduled major compaction tasks daily.
ObPartitionSpliter	RS	1	Schedules the compaction of partitions.
ObRebalanceTaskMgr	RS	1	Schedules the execution of load balancing tasks.
ObRootBackup	RS	1	Schedules backup tasks.
ObRootBalancer	RS	1	Generates load balancing tasks.
ObRsGtsMonitor	RS	1	Monitors the distribution of GTS instances and initiates tasks to migrate or generate GTS replicas based on the distribution of GTS replicas.
ObRsGtsTaskMgr	RS	1	Executes the tasks related to GTS replicas.
ObHeartbeatChecker	RS	1	Checks the status of heartbeats between OBServer nodes.
ObStandbyClusterSchemaProcessor	RS	1	Synchronizes the replica of a standby database to the user tenant schema of the primary database.
ObRestoreScheduler	RS	1	Schedules the restoration process.
ObWorkQueue	RS	4	Executes asynchronous RootServer tasks. The number of threads is determined by the `rootservice_async_task_thread_count` parameter. Value range: [1,10].
ObAsyncTaskQueue	RS	16	Executes the creation of indexes.
ObSwitchTaskQueue	RS	6	The task queue for primary/standby switchover in the physical standby database. The number of threads is determined by the `switchover_process_thread_count` parameter. Value range: [1,1000].
LocalityReload	RS	1	Regularly refreshes the locality information.
RSqlPool	RS	1	Allows the standby database to regularly maintain the RootServer list of the primary database.
ServerTracerTimer	RS	1	Schedules the tasks to maintain the status of other OBServer nodes.
LogEngine	CLOG	1	Collects and monitors the disk space occupied by clog files and recycles clog files.
CLGWR	CLOG	1	Writes clog items to the disk.
ClogHisRep	CLOG	3	Updates the internal table of the clog history when a partition goes online or offline.
BatchSubmitCtx	CLOG	1	Splits the transactions optimized in phase 1.
LogScanRunnable	CLOG	4	Scans all clog files when the OBServer node starts.
LogStateDri	CLOG	1	Switches the primary and standby replicas of the clog module and checks the status of the replica association.
ObElectionGCThread	Election	1	Recycles the memory of election objects.
Blacklist	CLOG	1	Detects network connection with the destination server.
BRPC	CLOG	5	Sends the batch_rpc aggregation package in the background.
CLOGReqMinor	CLOG	1	Triggers minor freezing based on the clog disk usage and speeds up the recycling of clog files.
LineCache	CLOG	1	Optimizes the synchronization of historical data in the liboblog scenario.
EXTLogWash	CLOG	1	Frequency: 100 ms.
CLogFileGC	CLOG	1	Regularly recycles clog files.
CKPTLogRep	CLOG	1	Used for the checkpoint operations of log replicas.
RebuildRetry	CLOG	1	Retries the partition rebuilding task.
ReplayEngine	CLOG	Physical core	Replays the clog files on the follower.
PxPoolTh	SQL	0	The thread pool for parallel execution.
sql_mem_timer	SQL	1	Automatically manages memory.
OmtNodeBalancer	Common	1	Refreshes multi-tenant information in the background.
MultiTenant	Common	1	Refreshes CPU utilization for multiple tenants to schedule resources.
SignalHandle	Common	1	Processes signals.
LeaseUpdate	Common	3	Monitors the lease between the RootServer and each OBServer node.
RsDDL	Common	1	Executes the DDL operations of the RootService.
MysqlIO	Common	12	Manages the connection with MySQL.
all_meta_table	Common	8	Reports the status of partition groups or partitions.
all_pg_partition_ meta_table	Common	8	Reports the status of partitions in a partition group.
TimerMonitor	Common	1	Monitors the actions of scheduled internal threads and triggers alerts for exceptions during execution.
ConfigMgr	Common	1	Refreshes parameters.
OB_ALOG	Common	1	Writes asynchronous system logs to the disk.
ELE_ALOG	Election	1	Writes asynchronous election module logs to the disk.

TsMgr

Trx

1

Refreshes the local GTS cache.

WeakReadSvr

Trx

1

Calculates the local server-level read timestamp of the standby IDC.

HAGtsSource

Trx

1

Refreshes ha_gts. The refresh frequency is determined by the gts_refresh_interval parameter.

GCPartAdpt

Trx

1

Regularly checks the all_tenant_gc_partition_info table to obtain the garbage collection (GC) information of partitions. The thread helps facilitate the GC and two-phase commit of transactions.

PartWorker

Trx

1

Traverses all partitions on the local OBServer node and performs the following operations:

Tries to write checkpoint logs at the transaction layer every 50 ms.
Calculates the snapshot points to be migrated every 15s.
Drives all active transactions in the current partition every 10s and checks the status of the scheduler. The thread helps clear the transaction context.
Checks the replica table status of the current partition every 10s.
Refreshes the clogs cached in the current partition every 10s.

LockWaitMgr

Trx

1

Wakes up the threads in the wait lock queue in hotspot row scenarios, such as statement timeout and session kill.

ClogAdapter

Trx

8

Asynchronously commits clogs at the transaction layer.

ObTransService

Trx

6

Performs the following operations:

Processes error messages during the transaction commit.
Retries a failed statement rollback.
Wakes up the subsequent transactions in an early lock release scenario.

GCCollector

Storage

1

Regularly checks whether GC operation can be performed on all partitions on the local OBServer nodes. If yes, triggers a GC operation.

RebuildSche

Storage

1

Regularly drives partition tasks that need to be rebuilt.

PurgeWorker

Storage

1

Deletes MemTable labels in the background.

DAG

Storage

16

The worker thread of dag, which is used to run tasks such as the minor compactions, major compactions, and migration of partitions.

DagScheduler

Storage

1

The scheduling thread of dag.

STableChecksumUp

Storage

1

Batch commits SSTable checksum tasks.

PartitionScheduler

Storage

2

Schedules minor compaction and major compaction tasks.

MemstoreGC

Storage

1

Recycles the frozen MemStore after a warm-up for minor compactions.

ObStoreFile

Storage

1

Checks for bad macroblocks and recycles macroblocks.

PartSerCb

Storage

40

Schedules 20 threads to handle the switchover of a partition leader.

ObPartitionSplit Worker

Storage

1

Splits a partition in the background.

FreezeTimer

Storage

1

Checks the MemStore memory and triggers a freezing task.

RebuildTask

Storage

1

Schedules the D replica to pull data.

IndexSche

Storage

1

Schedules the index creation task.

FreInfoReload

Storage

1

Synchronizes major freeze information in internal tables.

TableMgrGC

Storage

1

Recycles MemTable to release memory.

BackupInfoUpdate

Storage

1

Regularly refreshes backup data.

LogDiskMon

Storage

1

Detects the multiple disks of the system.

KVCacheWash

Storage

1

Cleans the memory of KVCache. The detection interval is determined by the _cache_wash_interval parameter. Default value: 200ms. Value range: [1ms,1m].

KVCacheRep

Storage

1

Manages memory fragments of the cache to recycle memory. The detection interval is determined by the _cache_wash_interval parameter. Default value: 200ms. Value range: [1ms,1m].

RSMonitor

RS

1

Monitors the status of the current RootService.

CacheCalculator

RS

1

Reserves memory for location_cache and schema_cache.

ObDailyMergeScheduler

RS

1

Schedules major compaction tasks.

ObEmptyServerChecker

RS

1

Detects whether an OBServer node has replicas.

ObFetchPrimaryDDLOperator

RS

1

Synchronizes the logic of the standby database to the schema of the sys tenant of the primary database.

ObFreezeInfoUpdater

RS

1

Speeds up the progress of freeze and manages the snapshot recovery points.

ObGlobalIndexBuilder

RS

1

Schedules the creation of global indexes.

ObGlobalMaxDecidedTransVersionMgr

RS

1

Collects the statistics of the versions of global maximum transactions.

ObLeaderCoordinator

RS

1

Manages the distribution of leader replicas in a cluster.

ObLogArchiveScheduler

RS

1

Archives the log files.

ObMajorFreezeLauncher

RS

1

Launches scheduled major compaction tasks daily.

ObPartitionSpliter

RS

1

Schedules the compaction of partitions.

ObRebalanceTaskMgr

RS

1

Schedules the execution of load balancing tasks.

ObRootBackup

RS

1

Schedules backup tasks.

ObRootBalancer

RS

1

Generates load balancing tasks.

ObRsGtsMonitor

RS

1

Monitors the distribution of GTS instances and initiates tasks to migrate or generate GTS replicas based on the distribution of GTS replicas.

ObRsGtsTaskMgr

RS

1

Executes the tasks related to GTS replicas.

ObHeartbeatChecker

RS

1

Checks the status of heartbeats between OBServer nodes.

ObStandbyClusterSchemaProcessor

RS

1

Synchronizes the replica of a standby database to the user tenant schema of the primary database.

ObRestoreScheduler

RS

1

Schedules the restoration process.

ObWorkQueue

RS

4

Executes asynchronous RootServer tasks. The number of threads is determined by the rootservice_async_task_thread_count parameter. Value range: [1,10].

ObAsyncTaskQueue

RS

16

Executes the creation of indexes.

ObSwitchTaskQueue

RS

6

The task queue for primary/standby switchover in the physical standby database. The number of threads is determined by the switchover_process_thread_count parameter. Value range: [1,1000].

LocalityReload

RS

1

Regularly refreshes the locality information.

RSqlPool

RS

1

Allows the standby database to regularly maintain the RootServer list of the primary database.

ServerTracerTimer

RS

1

Schedules the tasks to maintain the status of other OBServer nodes.

LogEngine

CLOG

1

Collects and monitors the disk space occupied by clog files and recycles clog files.

CLGWR

CLOG

1

Writes clog items to the disk.

ClogHisRep

CLOG

3

Updates the internal table of the clog history when a partition goes online or offline.

BatchSubmitCtx

CLOG

1

Splits the transactions optimized in phase 1.

LogScanRunnable

CLOG

4

Scans all clog files when the OBServer node starts.

LogStateDri

CLOG

1

Switches the primary and standby replicas of the clog module and checks the status of the replica association.

ObElectionGCThread

Election

1

Recycles the memory of election objects.

Blacklist

CLOG

1

Detects network connection with the destination server.

BRPC

CLOG

5

Sends the batch_rpc aggregation package in the background.

CLOGReqMinor

CLOG

1

Triggers minor freezing based on the clog disk usage and speeds up the recycling of clog files.

LineCache

CLOG

1

Optimizes the synchronization of historical data in the liboblog scenario.

EXTLogWash

CLOG

1

Frequency: 100 ms.

CLogFileGC

CLOG

1

Regularly recycles clog files.

CKPTLogRep

CLOG

1

Used for the checkpoint operations of log replicas.

RebuildRetry

CLOG

1

Retries the partition rebuilding task.

ReplayEngine

CLOG

Physical core

Replays the clog files on the follower.

PxPoolTh

SQL

0

The thread pool for parallel execution.

sql_mem_timer

SQL

1

Automatically manages memory.

OmtNodeBalancer

Common

1

Refreshes multi-tenant information in the background.

MultiTenant

Common

1

Refreshes CPU utilization for multiple tenants to schedule resources.

SignalHandle

Common

1

Processes signals.

LeaseUpdate

Common

3

Monitors the lease between the RootServer and each OBServer node.

RsDDL

Common

1

Executes the DDL operations of the RootService.

MysqlIO

Common

12

Manages the connection with MySQL.

all_meta_table

Common

8

Reports the status of partition groups or partitions.

all_pg_partition_ meta_table

Common

8

Reports the status of partitions in a partition group.

TimerMonitor

Common

1

Monitors the actions of scheduled internal threads and triggers alerts for exceptions during execution.

ConfigMgr

Common

1

Refreshes parameters.

OB_ALOG

Common

1

Writes asynchronous system logs to the disk.

ELE_ALOG

Election

1

Writes asynchronous election module logs to the disk.