---
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.
