Project: ClickHouse (App Definition and Development / Database)
File: scheduler.md

slug: /en/operations/system-tables/scheduler Contains information and status for residing on the local server. This table can be used for monitoring. The table contains a row for every scheduling node. Example: ``` sql SELECT * FROM system.scheduler WHERE resource = 'network_read' AND path = '/prio/fair/prod' FORMAT Vertical ``` ``` text Row 1: resource: network_read path: /prio/fair/prod type: fifo weight: 5 priority: 0 is_active: 0 active_children: 0 dequeued_requests: 67 canceled_requests: 0 dequeued_cost: 4692272 canceled_cost: 0 busy_periods: 63 vruntime: 938454.1999999989 system_vruntime: queue_length: 0 queue_cost: 0 budget: -60524 is_satisfied: inflight_requests: inflight_cost: max_requests: max_cost: max_speed: max_burst: throttling_us: tokens: ``` Columns: `resource` (`String`) - Resource name `path` (`String`) - Path to a scheduling node within this resource scheduling hierarchy `type` (`String`) - Type of a scheduling node. `weight` (`Float64`) - Weight of a node, used by a parent node of `fair`` type. `priority` (`Int64`) - Priority of a node, used by a parent node of 'priority' type (Lower value means higher priority). `is_active` (`UInt8`) - Whether this node is currently active - has resource requests to be dequeued and constraints satisfied. `active_children` (`UInt64`) - The number of children in active state. `dequeued_requests` (`UInt64`) - The total number of resource requests dequeued from this node. `canceled_requests` (`UInt64`) - The total number of resource requests canceled from this node. `dequeued_cost` (`UInt64`) - The sum of costs (e.g. size in bytes) of all requests dequeued from this node. `canceled_cost` (`UInt64`) - The sum of costs (e.g. size in bytes) of all requests canceled from this node. `busy_periods` (`UInt64`) - The total number of deactivations of this node. `vruntime` (`Nullable(Float64)`) - For children of `fair` nodes only. Virtual runtime of a node used by SFQ algorithm to select the next child to process in a max-min fair manner. `system_vruntime` (`Nullable(Float64)`) - For `fair` nodes only. Virtual runtime showing `vruntime` of the last processed resource request. Used during child activation as the new value of `vruntime`. `queue_length` (`Nullable(UInt64)`) - For `fifo` nodes only. Current number of resource requests residing in the queue. `queue_cost` (`Nullable(UInt64)`) - For `fifo` nodes only. Sum of costs (e.g. size in bytes) of all requests residing in the queue. `budget` (`Nullable(Int64)`) - For `fifo` nodes only. The number of available "cost units" for new resource requests. Can appear in case of discrepancy of estimated and real costs of resource requests (e.g. after read/write failure) `issatisfied` (`Nullable(UInt8)`) - For constraint nodes only (e.g. `inflightlimit`). Equals `1` if all the constraint of this node are satisfied. `inflightrequests` (`Nullable(Int64)`) - For `inflightlimit` nodes only. The number of resource requests dequeued from this node, that are currently in consumption state. `inflightcost` (`Nullable(Int64)`) - For `inflightlimit` nodes only. The sum of costs (e.g. bytes) of all resource requests dequeued from this node, that are currently in consumption state. `maxrequests` (`Nullable(Int64)`) - For `inflightlimit` nodes only. Upper limit for `inflight_requests` leading to constraint violation. `maxcost` (`Nullable(Int64)`) - For `inflightlimit` nodes only. Upper limit for `inflight_cost` leading to constraint violation. `maxspeed` (`Nullable(Float64)`) - For `bandwidthlimit` nodes only. Upper limit for bandwidth in tokens per second. `maxburst` (`Nullable(Float64)`) - For `bandwidthlimit` nodes only. Upper limit for `tokens` available in token-bucket throttler. `throttlingus` (`Nullable(Int64)`) - For `bandwidthlimit` nodes only. Total number of microseconds this node was in throttling state. `tokens` (`Nullable(Float64)`) - For `bandwidth_limit` nodes only. Number of tokens currently available in token-bucket throttler.