Concurrency events - Prefect

Concurrency events track when slots are acquired and released for named concurrency limits. For more on concurrency limits, see Global concurrency limits.

`prefect.concurrency-limit.acquired`

Emitted when concurrency slots are acquired for a named limit.

Resource

Label	Description
`prefect.resource.id`	`prefect.concurrency-limit.{uuid}`
`prefect.resource.name`	Concurrency limit name
`slots-acquired`	Number of slots acquired in this request
`limit`	Maximum number of slots for this limit

Resource ID pattern	Role	When present
`prefect.concurrency-limit.{uuid}`	`concurrency-limit`	One entry per other limit in the same acquisition batch (when acquiring multiple limits at once)

Payload

This event has no payload.

`prefect.concurrency-limit.released`

Emitted when concurrency slots are released for a named limit. Uses the follows field to link back to the corresponding acquired event.

Resource

Same as prefect.concurrency-limit.acquired.

Payload

This event has no payload.

Legacy v1 concurrency events

<Note> These events are emitted by the legacy tag-based concurrency limit system. For new concurrency limits, use global concurrency limits which emit the events documented above. </Note>

`prefect.concurrency-limit.v1.acquired`

Emitted when a legacy tag-based concurrency slot is acquired.

Resource

Label	Description
`prefect.resource.id`	`prefect.concurrency-limit.v1.{uuid}`
`prefect.resource.name`	Tag name
`limit`	Maximum number of slots
`task_run_id`	ID of the task run acquiring the slot

Related resources

Resource ID pattern	Role	When present
`prefect.concurrency-limit.v1.{uuid}`	`concurrency-limit`	One entry per other limit in the same acquisition batch

Payload

This event has no payload.

`prefect.concurrency-limit.v1.released`

Emitted when a legacy tag-based concurrency slot is released.

Resource

Same as prefect.concurrency-limit.v1.acquired.

Related resources

Same as prefect.concurrency-limit.v1.acquired.

Payload

This event has no payload.