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Workflow Execution Limits

This page discusses Workflow Execution limits, Workflow Execution Callback limits, and Nexus Operation limits.

Limits​

There is no limit to the number of concurrent Workflow Executions, albeit you must abide by the Workflow Execution's Event History limit.

caution

As a precautionary measure, the Workflow Execution's Event History is limited to 51,200 Events or 50 MB and will warn you after 10,240 Events or 10 MB.

There is also a limit to the number of certain types of incomplete operations.

Each in-progress Activity generates a metadata entry in the Workflow Execution's mutable state. Too many entries in a single Workflow Execution's mutable state causes unstable persistence. To protect the system, Temporal enforces a maximum number of incomplete Activities, Child Workflows, Signals, or Cancellation requests per Workflow Execution (by default, 2,000 for each type of operation). Once the limit is reached for a type of operation, if the Workflow Execution attempts to start another operation of that type (by producing a ScheduleActivityTask, StartChildWorkflowExecution, SignalExternalWorkflowExecution, or RequestCancelExternalWorkflowExecution Command), it will be unable to (the Workflow Task Execution will fail and get retried).

These limits are set with the following dynamic configuration keys:

  • NumPendingActivitiesLimit
  • NumPendingChildExecutionsLimit
  • NumPendingSignalsLimit
  • NumPendingCancelRequestsLimit

Workflow Execution Callback limits​

There is a limit to the total number of Workflow Callbacks that may be attached to a single Workflow Execution (by default, 32 Workflow Callbacks). Attaching multiple Nexus callers to a handler Workflow may exceed these limits.

These limits can be set with the following dynamic configuration keys:

  • MaxCallbacksPerWorkflow

Workflow Execution Nexus Operation Limits​

There is a limit to the maximum number of Nexus Operations in a Workflow before Continue-As-New is required. Each in-progress Nexus Operation generates a metadata entry in the Workflow Execution's mutable state. Too many entries in a single Workflow Execution's mutable state causes unstable persistence. To protect the system, Temporal enforces a maximum number of incomplete Nexus Operation requests per Workflow Execution (by default, 30 Nexus Operations). Once the limit is reached for a type of operation, if the Workflow Execution attempts to start another Nexus operation (by producing a ScheduleNexusOperation), it will be unable to do so (the Workflow Task Execution will fail and get retried).

These limits are set with the following dynamic configuration keys:

  • MaxConcurrentOperations