workflow-execution

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Workflow ID uniqueness within a Namespace

Temporal guarantees that there can be at most one Workflow Execution with a given Workflow ID running at any point in time. This uniqueness constraint is enforced within the active Namespace. On a High Availability Namespace, replication is asynchronous and failover preserves the constraint through Temporal Cloud's conflict resolution process.

Run ID definition and mutability

A Run ID is a globally unique, platform-level identifier for a Workflow Execution. The current Run ID is mutable and can change during a Workflow Retry. You should not rely on storing the current Run ID or use it for logical choices, because a Workflow Retry changes the Run ID and can lead to non-determinism issues.

Run ID across Workflow Execution chains

A Run ID uniquely identifies a Workflow Execution even if it shares a Workflow ID with other Workflow Executions. Operations like ContinueAsNew, Retry, Cron, and Reset create a Workflow Execution Chain. Each operation creates a new Workflow Execution inside a chain run. The first_execution_run_id is the Run ID of the first Workflow Execution in a chain run, and the original_execution_run_id is the Run ID when the WorkflowExecutionStarted event occurs.

Workflow Reset behavior with Run IDs

A Workflow Reset changes the first execution Run ID but preserves the original execution Run ID. When a new Workflow Execution in the chain starts, it stores its Run ID in original_execution_run_id. A reset does not change that field, but the current Run ID is updated.

Workflow ID definition and characteristics

A Workflow ID is a customizable, application-level identifier for a Workflow Execution that is unique to an Open Workflow Execution within a Namespace. It is meant to be a business-process identifier, such as a customer identifier or order identifier.

Workflow ID Reuse Policy values

The Workflow ID Reuse Policy can have the following values: (1) Allow Duplicate (default) - The Workflow Execution is allowed to exist regardless of the Closed status of a previous Workflow Execution with the same Workflow ID; (2) Allow Duplicate Failed Only - The Workflow Execution is allowed to exist only if a previous Workflow Execution with the same Workflow ID does not have a Completed status; (3) Reject Duplicate - The Workflow Execution cannot exist if a previous Workflow Execution has the same Workflow ID, regardless of Closed status; (4) Terminate if Running - Only applies to Workflow Executions currently open within the Namespace, and Retention Period is not a consideration for this policy.

Workflow ID Conflict Policy values

The Workflow ID Conflict Policy determines how to resolve a conflict when spawning a new Workflow Execution with a Workflow ID used by an existing Open Workflow Execution. The policy can have the following values: (1) Fail (default) - Prevents the Workflow Execution from spawning and returns a 'Workflow execution already started' error; (2) Use Existing - Prevents the Workflow Execution from spawning and returns a successful response with the Open Workflow Execution's Run ID; (3) Terminate Existing - Terminates the Open Workflow Execution then spawns the new Workflow Execution with the same Workflow ID.

Workflow Execution unique identification across Namespaces

A Workflow Execution can be uniquely identified across all Namespaces by its Namespace, Workflow ID, and Run ID.

Scheduled Workflows and multiple runs

When running the same Workflow at recurring intervals using the Schedules feature, there can be multiple runs of a single Workflow Execution over a period of time. All runs will have the same Workflow ID, but each run will have a unique system-generated Run ID.

Cron Job as Workflow Execution chain

A Temporal Cron Job is a chain of Workflow Executions that all have the same Workflow ID. Each Workflow Execution within the chain is considered a Run.

Workflow ID Conflict Policy and Reuse Policy distinction

Workflow ID Reuse Policy manages whether a Workflow ID from a Closed Workflow can be re-used. Workflow ID Conflict Policy determines how to resolve a conflict when spawning a new Workflow Execution with a Workflow ID used by an existing Open Workflow Execution. It is not possible for a new Workflow Execution to spawn with the same Workflow ID as another Open Workflow Execution, regardless of the Workflow ID Reuse Policy.

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