--- slug: /en/operations/system-tables/metrics --- # metrics 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. Columns: - `metric` ([String](../../sql-reference/data-types/string.md)) — Metric name. - `value` ([Int64](../../sql-reference/data-types/int-uint.md)) — Metric value. - `description` ([String](../../sql-reference/data-types/string.md)) — Metric description. - `name` ([String](../../sql-reference/data-types/string.md)) — Alias for `metric`. You can find all supported metrics in source file [src/Common/CurrentMetrics.cpp](https://github.com/ClickHouse/ClickHouse/blob/master/src/Common/CurrentMetrics.cpp). **Example** ``` sql SELECT * FROM system.metrics LIMIT 10 ``` ``` text ┌─metric───────────────────────────────┬─value─┬─description────────────────────────────────────────────────────────────┐ │ Query │ 1 │ Number of executing queries │ │ Merge │ 0 │ Number of executing background merges │ │ PartMutation │ 0 │ Number of mutations (ALTER DELETE/UPDATE) │ │ ReplicatedFetch │ 0 │ Number of data parts being fetched from replicas │ │ ReplicatedSend │ 0 │ Number of data parts being sent to replicas │ │ ReplicatedChecks │ 0 │ Number of data parts checking for consistency │ │ BackgroundMergesAndMutationsPoolTask │ 0 │ Number of active merges and mutations in an associated background pool │ │ BackgroundFetchesPoolTask │ 0 │ Number of active fetches in an associated background pool │ │ BackgroundCommonPoolTask │ 0 │ Number of active tasks in an associated background pool │ │ BackgroundMovePoolTask │ 0 │ Number of active tasks in BackgroundProcessingPool for moves │ └──────────────────────────────────────┴───────┴────────────────────────────────────────────────────────────────────────┘ ``` ## Metric descriptions ### AggregatorThreads Number of threads in the Aggregator thread pool. ### AggregatorThreadsActive Number of threads in the Aggregator thread pool running a task. ### TablesLoaderForegroundThreads Number of threads in the async loader foreground thread pool. ### TablesLoaderForegroundThreadsActive Number of threads in the async loader foreground thread pool running a task. ### TablesLoaderBackgroundThreads Number of threads in the async loader background thread pool. ### TablesLoaderBackgroundThreadsActive Number of threads in the async loader background 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. ### 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 prefetch 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 ### KeeperOutstandingRequests 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. ### 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. ### 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 ### 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. **See Also** - [system.asynchronous_metrics](../../operations/system-tables/asynchronous_metrics.md#system_tables-asynchronous_metrics) — Contains periodically calculated metrics. - [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.