Contains metrics which can be calculated instantly, or have a current value. For example, the number of simultaneously processed queries or the current replica delay. This table is always up to date.
The list of supported metrics you can find in the [src/Common/CurrentMetrics.cpp](https://github.com/ClickHouse/ClickHouse/blob/master/src/Common/CurrentMetrics.cpp) source file of ClickHouse.
Number of threads in the Aggregator thread pool running a task.
### AsyncInsertCacheSize
Number of async insert hash id in cache
### AsynchronousInsertThreads
Number of threads in the AsynchronousInsert thread pool.
### AsynchronousInsertThreadsActive
Number of threads in the AsynchronousInsert thread pool running a task.
### AsynchronousReadWait
Number of threads waiting for asynchronous read.
### BackgroundBufferFlushSchedulePoolSize
Limit on number of tasks in BackgroundBufferFlushSchedulePool
### BackgroundBufferFlushSchedulePoolTask
Number of active tasks in BackgroundBufferFlushSchedulePool. This pool is used for periodic Buffer flushes
### BackgroundCommonPoolSize
Limit on number of tasks in an associated background pool
### BackgroundCommonPoolTask
Number of active tasks in an associated background pool
### BackgroundDistributedSchedulePoolSize
Limit on number of tasks in BackgroundDistributedSchedulePool
### BackgroundDistributedSchedulePoolTask
Number of active tasks in BackgroundDistributedSchedulePool. This pool is used for distributed sends that is done in background.
### BackgroundFetchesPoolSize
Limit on number of simultaneous fetches in an associated background pool
### BackgroundFetchesPoolTask
Number of active fetches in an associated background pool
### BackgroundMergesAndMutationsPoolSize
Limit on number of active merges and mutations in an associated background pool
### BackgroundMergesAndMutationsPoolTask
Number of active merges and mutations in an associated background pool
### BackgroundMessageBrokerSchedulePoolSize
Limit on number of tasks in BackgroundProcessingPool for message streaming
### BackgroundMessageBrokerSchedulePoolTask
Number of active tasks in BackgroundProcessingPool for message streaming
### BackgroundMovePoolSize
Limit on number of tasks in BackgroundProcessingPool for moves
### BackgroundMovePoolTask
Number of active tasks in BackgroundProcessingPool for moves
### BackgroundSchedulePoolSize
Limit on number of tasks in BackgroundSchedulePool. This pool is used for periodic ReplicatedMergeTree tasks, like cleaning old data parts, altering data parts, replica re-initialization, etc.
### BackgroundSchedulePoolTask
Number of active tasks in BackgroundSchedulePool. This pool is used for periodic ReplicatedMergeTree tasks, like cleaning old data parts, altering data parts, replica re-initialization, etc.
### BackupsIOThreads
Number of threads in the BackupsIO thread pool.
### BackupsIOThreadsActive
Number of threads in the BackupsIO thread pool running a task.
### BackupsThreads
Number of threads in the thread pool for BACKUP.
### BackupsThreadsActive
Number of threads in thread pool for BACKUP running a task.
### BrokenDistributedFilesToInsert
Number of files for asynchronous insertion into Distributed tables that has been marked as broken. This metric will starts from 0 on start. Number of files for every shard is summed.
### CacheDetachedFileSegments
Number of existing detached cache file segments
### CacheDictionaryThreads
Number of threads in the CacheDictionary thread pool.
### CacheDictionaryThreadsActive
Number of threads in the CacheDictionary thread pool running a task.
### CacheDictionaryUpdateQueueBatches
Number of 'batches' (a set of keys) in update queue in CacheDictionaries.
### CacheDictionaryUpdateQueueKeys
Exact number of keys in update queue in CacheDictionaries.
### CacheFileSegments
Number of existing cache file segments
### ContextLockWait
Number of threads waiting for lock in Context. This is global lock.
### DDLWorkerThreads
Number of threads in the DDLWorker thread pool for ON CLUSTER queries.
### DDLWorkerThreadsActive
Number of threads in the DDLWORKER thread pool for ON CLUSTER queries running a task.
### DatabaseCatalogThreads
Number of threads in the DatabaseCatalog thread pool.
### DatabaseCatalogThreadsActive
Number of threads in the DatabaseCatalog thread pool running a task.
### DatabaseOnDiskThreads
Number of threads in the DatabaseOnDisk thread pool.
### DatabaseOnDiskThreadsActive
Number of threads in the DatabaseOnDisk thread pool running a task.
### DatabaseOrdinaryThreads
Number of threads in the Ordinary database thread pool.
### DatabaseOrdinaryThreadsActive
Number of threads in the Ordinary database thread pool running a task.
### DelayedInserts
Number of INSERT queries that are throttled due to high number of active data parts for partition in a MergeTree table.
### DestroyAggregatesThreads
Number of threads in the thread pool for destroy aggregate states.
### DestroyAggregatesThreadsActive
Number of threads in the thread pool for destroy aggregate states running a task.
### DictCacheRequests
Number of requests in fly to data sources of dictionaries of cache type.
### DiskObjectStorageAsyncThreads
Number of threads in the async thread pool for DiskObjectStorage.
### DiskObjectStorageAsyncThreadsActive
Number of threads in the async thread pool for DiskObjectStorage running a task.
### DiskSpaceReservedForMerge
Disk space reserved for currently running background merges. It is slightly more than the total size of currently merging parts.
### DistributedFilesToInsert
Number of pending files to process for asynchronous insertion into Distributed tables. Number of files for every shard is summed.
### DistributedSend
Number of connections to remote servers sending data that was INSERTed into Distributed tables. Both synchronous and asynchronous mode.
### EphemeralNode
Number of ephemeral nodes hold in ZooKeeper.
### FilesystemCacheElements
Filesystem cache elements (file segments)
### FilesystemCacheReadBuffers
Number of active cache buffers
### FilesystemCacheSize
Filesystem cache size in bytes
### GlobalThread
Number of threads in global thread pool.
### GlobalThreadActive
Number of threads in global thread pool running a task.
### HTTPConnection
Number of connections to HTTP server
### HashedDictionaryThreads
Number of threads in the HashedDictionary thread pool.
### HashedDictionaryThreadsActive
Number of threads in the HashedDictionary thread pool running a task.
### IOPrefetchThreads
Number of threads in the IO prefertch thread pool.
### IOPrefetchThreadsActive
Number of threads in the IO prefetch thread pool running a task.
### IOThreads
Number of threads in the IO thread pool.
### IOThreadsActive
Number of threads in the IO thread pool running a task.
### IOUringInFlightEvents
Number of io_uring SQEs in flight
### IOUringPendingEvents
Number of io_uring SQEs waiting to be submitted
### IOWriterThreads
Number of threads in the IO writer thread pool.
### IOWriterThreadsActive
Number of threads in the IO writer thread pool running a task.
### InterserverConnection
Number of connections from other replicas to fetch parts
### KafkaAssignedPartitions
Number of partitions Kafka tables currently assigned to
### KafkaBackgroundReads
Number of background reads currently working (populating materialized views from Kafka)
### KafkaConsumers
Number of active Kafka consumers
### KafkaConsumersInUse
Number of consumers which are currently used by direct or background reads
### KafkaConsumersWithAssignment
Number of active Kafka consumers which have some partitions assigned.
### KafkaLibrdkafkaThreads
Number of active librdkafka threads
### KafkaProducers
Number of active Kafka producer created
### KafkaWrites
Number of currently running inserts to Kafka
### KeeperAliveConnections
Number of alive connections
### KeeperOutstandingRequets
Number of outstanding requests
### LocalThread
Number of threads in local thread pools. The threads in local thread pools are taken from the global thread pool.
### LocalThreadActive
Number of threads in local thread pools running a task.
### MMappedAllocBytes
Sum bytes of mmapped allocations
### MMappedAllocs
Total number of mmapped allocations
### MMappedFileBytes
Sum size of mmapped file regions.
### MMappedFiles
Total number of mmapped files.
### MarksLoaderThreads
Number of threads in thread pool for loading marks.
### MarksLoaderThreadsActive
Number of threads in the thread pool for loading marks running a task.
### MaxDDLEntryID
Max processed DDL entry of DDLWorker.
### MaxPushedDDLEntryID
Max DDL entry of DDLWorker that pushed to zookeeper.
### MemoryTracking
Total amount of memory (bytes) allocated by the server.
### Merge
Number of executing background merges
### MergeTreeAllRangesAnnouncementsSent
The current number of announcement being sent in flight from the remote server to the initiator server about the set of data parts (for MergeTree tables). Measured on the remote server side.
### MergeTreeBackgroundExecutorThreads
Number of threads in the MergeTreeBackgroundExecutor thread pool.
### MergeTreeBackgroundExecutorThreadsActive
Number of threads in the MergeTreeBackgroundExecutor thread pool running a task.
### MergeTreeDataSelectExecutorThreads
Number of threads in the MergeTreeDataSelectExecutor thread pool.
### MergeTreeDataSelectExecutorThreadsActive
Number of threads in the MergeTreeDataSelectExecutor thread pool running a task.
### MergeTreePartsCleanerThreads
Number of threads in the MergeTree parts cleaner thread pool.
### MergeTreePartsCleanerThreadsActive
Number of threads in the MergeTree parts cleaner thread pool running a task.
### MergeTreePartsLoaderThreads
Number of threads in the MergeTree parts loader thread pool.
### MergeTreePartsLoaderThreadsActive
Number of threads in the MergeTree parts loader thread pool running a task.
### MergeTreeReadTaskRequestsSent
The current number of callback requests in flight from the remote server back to the initiator server to choose the read task (for MergeTree tables). Measured on the remote server side.
### Move
Number of currently executing moves
### MySQLConnection
Number of client connections using MySQL protocol
### NetworkReceive
Number of threads receiving data from network. Only ClickHouse-related network interaction is included, not by 3rd party libraries.
### NetworkSend
Number of threads sending data to network. Only ClickHouse-related network interaction is included, not by 3rd party libraries.
### OpenFileForRead
Number of files open for reading
### OpenFileForWrite
Number of files open for writing
### ParallelFormattingOutputFormatThreads
Number of threads in the ParallelFormattingOutputFormatThreads thread pool.
### ParallelFormattingOutputFormatThreadsActive
Number of threads in the ParallelFormattingOutputFormatThreads thread pool running a task.
### ParallelParsingInputFormatThreads
Number of threads in the ParallelParsingInputFormat thread pool.
### ParallelParsingInputFormatThreadsActive
Number of threads in the ParallelParsingInputFormat thread pool running a task.
### PartMutation
Number of mutations (ALTER DELETE/UPDATE)
### PartsActive
Active data part, used by current and upcoming SELECTs.
### PartsCommitted
Deprecated. See PartsActive.
### PartsCompact
Compact parts.
### PartsDeleteOnDestroy
Part was moved to another disk and should be deleted in own destructor.
### PartsDeleting
Not active data part with identity refcounter, it is deleting right now by a cleaner.
### PartsInMemory
In-memory parts.
### PartsOutdated
Not active data part, but could be used by only current SELECTs, could be deleted after SELECTs finishes.
### PartsPreActive
The part is in data_parts, but not used for SELECTs.
### PartsPreCommitted
Deprecated. See PartsPreActive.
### PartsTemporary
The part is generating now, it is not in data_parts list.
### PartsWide
Wide parts.
### PendingAsyncInsert
Number of asynchronous inserts that are waiting for flush.
### PostgreSQLConnection
Number of client connections using PostgreSQL protocol
### Query
Number of executing queries
### QueryPreempted
Number of queries that are stopped and waiting due to 'priority' setting.
### QueryThread
Number of query processing threads
### RWLockActiveReaders
Number of threads holding read lock in a table RWLock.
### RWLockActiveWriters
Number of threads holding write lock in a table RWLock.
### RWLockWaitingReaders
Number of threads waiting for read on a table RWLock.
### RWLockWaitingWriters
Number of threads waiting for write on a table RWLock.
### Read
Number of read (read, pread, io_getevents, etc.) syscalls in fly
### ReadTaskRequestsSent
The current number of callback requests in flight from the remote server back to the initiator server to choose the read task (for s3Cluster table function and similar). Measured on the remote server side.
### ReadonlyReplica
Number of Replicated tables that are currently in readonly state due to re-initialization after ZooKeeper session loss or due to startup without ZooKeeper configured.
### RemoteRead
Number of read with remote reader in fly
### ReplicatedChecks
Number of data parts checking for consistency
### ReplicatedFetch
Number of data parts being fetched from replica
### ReplicatedSend
Number of data parts being sent to replicas
### RestartReplicaThreads
Number of threads in the RESTART REPLICA thread pool.
### RestartReplicaThreadsActive
Number of threads in the RESTART REPLICA thread pool running a task.
### RestoreThreads
Number of threads in the thread pool for RESTORE.
### RestoreThreadsActive
Number of threads in the thread pool for RESTORE running a task.
### Revision
Revision of the server. It is a number incremented for every release or release candidate except patch releases.
### S3Requests
S3 requests
### SendExternalTables
Number of connections that are sending data for external tables to remote servers. External tables are used to implement GLOBAL IN and GLOBAL JOIN operators with distributed subqueries.
### SendScalars
Number of connections that are sending data for scalars to remote servers.
### StartupSystemTablesThreads
Number of threads in the StartupSystemTables thread pool.
### StartupSystemTablesThreadsActive
Number of threads in the StartupSystemTables thread pool running a task.
### StorageBufferBytes
Number of bytes in buffers of Buffer tables
### StorageBufferRows
Number of rows in buffers of Buffer tables
### StorageDistributedThreads
Number of threads in the StorageDistributed thread pool.
### StorageDistributedThreadsActive
Number of threads in the StorageDistributed thread pool running a task.
### StorageHiveThreads
Number of threads in the StorageHive thread pool.
### StorageHiveThreadsActive
Number of threads in the StorageHive thread pool running a task.
### StorageS3Threads
Number of threads in the StorageS3 thread pool.
### StorageS3ThreadsActive
Number of threads in the StorageS3 thread pool running a task.
### SystemReplicasThreads
Number of threads in the system.replicas thread pool.
### SystemReplicasThreadsActive
Number of threads in the system.replicas thread pool running a task.
### TCPConnection
Number of connections to TCP server (clients with native interface), also included server-server distributed query connections
### TablesLoaderThreads
Number of threads in the tables loader thread pool.
### TablesLoaderThreadsActive
Number of threads in the tables loader thread pool running a task.
### TablesToDropQueueSize
Number of dropped tables, that are waiting for background data removal.
### TemporaryFilesForAggregation
Number of temporary files created for external aggregation
### TemporaryFilesForJoin
Number of temporary files created for JOIN
### TemporaryFilesForSort
Number of temporary files created for external sorting
### TemporaryFilesUnknown
Number of temporary files created without known purpose
### ThreadPoolFSReaderThreads
Number of threads in the thread pool for local_filesystem_read_method=threadpool.
### ThreadPoolFSReaderThreadsActive
Number of threads in the thread pool for local_filesystem_read_method=threadpool running a task.
### ThreadPoolRemoteFSReaderThreads
Number of threads in the thread pool for remote_filesystem_read_method=threadpool.
### ThreadPoolRemoteFSReaderThreadsActive
Number of threads in the thread pool for remote_filesystem_read_method=threadpool running a task.
### ThreadsInOvercommitTracker
Number of waiting threads inside of OvercommitTracker
### TotalTemporaryFiles
Number of temporary files created
### VersionInteger
Version of the server in a single integer number in base-1000. For example, version 11.22.33 is translated to 11022033.
### Write
Number of write (write, pwrite, io_getevents, etc.) syscalls in fly
### ZooKeeperRequest
Number of requests to ZooKeeper in fly.
### ZooKeeperSession
Number of sessions (connections) to ZooKeeper. Should be no more than one, because using more than one connection to ZooKeeper may lead to bugs due to lack of linearizability (stale reads) that ZooKeeper consistency model allows.
### ZooKeeperWatch
Number of watches (event subscriptions) in ZooKeeper.
- [system.events](../../operations/system-tables/events.md#system_tables-events) — Contains a number of events that occurred.
- [system.metric_log](../../operations/system-tables/metric_log.md#system_tables-metric_log) — Contains a history of metrics values from tables `system.metrics` and `system.events`.
- [Monitoring](../../operations/monitoring.md) — Base concepts of ClickHouse monitoring.
