ClickHouse/docs/en/operations/system-tables/scheduler.md

slug
/en/operations/system-tables/scheduler

scheduler

Contains information and status for scheduling nodes residing on the local server. This table can be used for monitoring. The table contains a row for every scheduling node.

Example:

SELECT *
FROM system.scheduler
WHERE resource = 'network_read' AND path = '/prio/fair/prod'
FORMAT Vertical

Row 1:
──────
resource:          network_read
path:              /prio/fair/prod
type:              fifo
weight:            5
priority:          0
is_active:         0
active_children:   0
dequeued_requests: 67
dequeued_cost:     4692272
busy_periods:      63
vruntime:          938454.1999999989
system_vruntime:   ᴺᵁᴸᴸ
queue_length:      0
queue_cost:        0
budget:            -60524
is_satisfied:      ᴺᵁᴸᴸ
inflight_requests: ᴺᵁᴸᴸ
inflight_cost:     ᴺᵁᴸᴸ
max_requests:      ᴺᵁᴸᴸ
max_cost:          ᴺᵁᴸᴸ
max_speed:         ᴺᵁᴸᴸ
max_burst:         ᴺᵁᴸᴸ
throttling_us:     ᴺᵁᴸᴸ
tokens:            ᴺᵁᴸᴸ

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.
• dequeued_cost (UInt64) - The sum of costs (e.g. size in bytes) of all requests dequeued 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)
• is_satisfied (Nullable(UInt8)) - For constraint nodes only (e.g. inflight_limit). Equals 1 if all the constraint of this node are satisfied.
• inflight_requests (Nullable(Int64)) - For inflight_limit nodes only. The number of resource requests dequeued from this node, that are currently in consumption state.
• inflight_cost (Nullable(Int64)) - For inflight_limit nodes only. The sum of costs (e.g. bytes) of all resource requests dequeued from this node, that are currently in consumption state.
• max_requests (Nullable(Int64)) - For inflight_limit nodes only. Upper limit for inflight_requests leading to constraint violation.
• max_cost (Nullable(Int64)) - For inflight_limit nodes only. Upper limit for inflight_cost leading to constraint violation.
• max_speed (Nullable(Float64)) - For bandwidth_limit nodes only. Upper limit for bandwidth in tokens per second.
• max_burst (Nullable(Float64)) - For bandwidth_limit nodes only. Upper limit for tokens available in token-bucket throttler.
• throttling_us (Nullable(Int64)) - For bandwidth_limit 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.