| Ack level | The checkpointed position below which all tasks in a category are complete. | service/history/queues · GitHub service/history/shard · GitHub | docs · glossary |
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| Activity Definition / Activity Type | The user function implementing an Activity and the name that maps to it; registered on the worker. | sdk · SDK repositories
| docs · glossary |
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| Activity Execution | The full chain of attempts for one scheduled Activity, from schedule to final result. | service/history/workflow · GitHub service/history/api/respondactivitytaskcompleted · GitHub service/history/api/respondactivitytaskfailed · GitHub service/history/api/respondactivitytaskcanceled · GitHub service/history/api/pauseactivity · GitHub service/history/api/resetactivity · GitHub service/history/api/updateactivityoptions · GitHub | docs · glossary |
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| Activity Heartbeat | A periodic progress ping recorded in mutable state and checked by the heartbeat timeout timer. | service/history/api/recordactivitytaskheartbeat · GitHub service/history/queues · GitHub | docs · glossary |
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| Activity Task | A task carrying the input and context for one Activity attempt, dispatched by Matching after History schedules it. | service/history/queues · GitHub service/matching · GitHub service/history/api/recordactivitytaskstarted · GitHub service/history/api/isactivitytaskvalid · GitHub | docs · glossary |
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| Archival | Copies closed histories and visibility records to blob storage after retention, driven by the history archival queue. | | docs · glossary |
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| Asynchronous Activity Completion | An Activity returns pending and an external system completes it later by Task Token. | | docs · glossary |
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| Authorizer Plugin / Claim Mapper | Server plugins that extract claims from a JWT and authorize each API call. | | docs · glossary |
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| Backlog / spool | Tasks persisted because no poller was waiting; classic, priority, and fairness variants. | | docs · glossary |
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| Buffered events | Events that arrive while a Workflow Task is in flight, held until the task completes. | service/history/historybuilder · GitHub service/history/workflow · GitHub | docs · glossary |
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| CHASM | Coordinated Heterogeneous Application State Machines: a component-tree framework that lets non-workflow archetypes share the shard substrate. | | docs · glossary |
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| Child Workflow | A workflow started from inside another; the parent is notified of its close through a cross-shard RPC. | service/history/queues · GitHub service/history/api/recordchildworkflowcompleted · GitHub service/history/api/verifychildworkflowcompletionrecorded · GitHub | docs · glossary |
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| Command | A requested action a worker returns after a Workflow Task; the server validates it and writes Events. | service/history/workflow · GitHub service/history/api/respondworkflowtaskcompleted · GitHub | docs · glossary |
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| Continue-As-New | Closes the current run and atomically starts a new run of the same Workflow ID with a fresh Event History. | service/history/workflow · GitHub service/history/api/respondworkflowtaskcompleted · GitHub | docs · glossary |
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| Delay Workflow Execution | A start option that delays the first Workflow Task by a backoff timer. | service/history/api/startworkflow · GitHub service/history/queues · GitHub | docs · glossary |
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| Dual Visibility | Running a secondary Visibility store during a migration. | | docs · glossary |
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| Dynamic config | Typed, hot-reloadable settings keyed by namespace, task queue, or shard. | | docs · glossary |
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| Event | A record the server appends to history from an external occurrence or a Command. | service/history/historybuilder · GitHub service/history/events · GitHub api/history/v1 · GitHub | docs · glossary |
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| Event History | The append-only log of Events for one execution, stored as a tree of branches of event batches. | common/persistence · diagram · GitHub service/history/events · GitHub service/history/api/getworkflowexecutionhistory · GitHub service/history/api/getworkflowexecutionrawhistoryv2 · GitHub | docs · glossary |
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| Failover version / version history | Per-event version numbers tied to the active cluster so replication can detect and resolve conflicting branches. | | docs · glossary |
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| Failure / Failure Converter | Temporal's typed error model carried in Events and across SDKs. | | docs · glossary |
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| Frontend Service | The stateless gateway that authenticates, rate-limits, validates the namespace, and routes every call to History or Matching. | | docs · glossary |
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| Global Namespace / Failover | A namespace replicated to a standby cluster, and the handover of its active cluster. | | docs · glossary |
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| Heartbeat / Start-To-Close / Schedule-To-Close / Schedule-To-Start Timeouts | Activity timeouts, each persisted as the next timer task per activity and enforced by the timer queue. | service/history/queues · GitHub service/history/workflow · GitHub | docs · glossary |
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| History branch / tree | Executions can fork on reset or conflict resolution; the tree records branches and nodes store event batches. | | docs · glossary |
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| History Service | The stateful core that owns execution state and Event History and runs the internal task queues. | | docs · glossary |
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| History Shard | A fixed-count partition of the execution space, owned by one History host at a time; requests route by hashing namespace and workflow ID. | | docs · glossary |
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| HSM (hierarchical state machines) | The older framework for typed state machines inside mutable state, used for callbacks and Nexus operations. | service/history/hsm · GitHub service/history/hsm/callbacks · GitHub service/history/hsm/nexusoperations · GitHub | docs · glossary |
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| Idempotency | Designing Activities so repeats have one effect, because delivery is at-least-once. | sdk · SDK repositories
| docs · glossary |
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| Internal service clients | Typed gRPC clients between services, layered with metrics and retries, that resolve the owning host through membership. | | docs · glossary |
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| List Filter | The SQL-like query string accepted by list and count APIs. | | docs · glossary |
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| Local Activity | An Activity executed inside the worker's Workflow Task, recorded as a marker Event. | sdk · SDK repositories service/history/workflow · GitHub | docs · glossary |
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| Matching Service | Hosts Task Queues and matches tasks from History to worker long-polls, in memory or via a persisted backlog. | service/matching · GitHub service/matching/configs · GitHub api/matchingservice/v1 · GitHub | docs · glossary |
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| Memo | Non-indexed user metadata on an execution, returned by describe and list. | | docs · glossary |
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| Message protocol (Update) | The worker-to-server message protocol carrying Update requests and responses alongside Workflow Tasks. | | docs · glossary |
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| Multi-Cluster Replication | Async replication of executions to passive clusters over per-shard streams, with version-history conflict resolution. | service/history/replication · GitHub service/history/replication/eventhandler · GitHub service/history/ndc · GitHub service/history/api/replication · GitHub service/worker/replicator · GitHub common/cluster · diagram · GitHub api/replication/v1 · GitHub | docs · glossary |
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| Mutable state | The materialized per-execution state record held in the executions row and cached on the owning History host. | service/history/workflow · GitHub service/history/workflow/cache · GitHub service/history/interfaces · GitHub service/history/api/describemutablestate · GitHub api/persistence/v1 · GitHub | docs · glossary |
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| Namespace | The unit of isolation that scopes workflow IDs, task queues, retention, search attributes, and replication. | | docs · glossary |
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| Nexus Async Completion Callback | The HTTP callback a handler posts to when an async operation finishes, routed to the caller's History. | | docs · glossary |
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| Nexus Endpoint | A named reverse proxy routing a Nexus Service to a namespace and task queue or an external URL. | | docs · glossary |
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| Nexus Machinery | At-least-once delivery of operation start, cancel, and completion across namespace boundaries. | | docs · glossary |
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| Nexus Operation | One operation on a Nexus Service; the caller side is a state machine (HSM today, CHASM behind a flag) driven by the outbound queue. | service/history/hsm/nexusoperations · GitHub service/history/hsm/nexusoperations/workflow · GitHub chasm/lib/nexusoperation · GitHub service/history/queues · GitHub | docs · glossary |
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| Nexus Operation Handler / Nexus Service | Worker code implementing operations; dispatched from Frontend through Matching to a polling worker. | service/frontend · GitHub service/matching · GitHub sdk · SDK repositories | docs · glossary |
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| Nexus Registry | The cluster-wide endpoint store, owned by one Matching node and polled by others. | | docs · glossary |
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| Nexus RPC | The open protocol for arbitrary-duration operations with sync and async completion. | | docs · glossary |
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| Nexus Standalone Activity | An operation backed by a Standalone Activity. | chasm/lib/activity · GitHub chasm/lib/nexusoperation · GitHub | docs · glossary |
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| Parent Close Policy | What happens to children when the parent closes: terminate, cancel, or abandon. | service/worker/parentclosepolicy · GitHub service/history/queues · GitHub | docs · glossary |
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| Patching | SDK markers in history so new code can branch on whether an old execution passed a change point. | sdk · SDK repositories service/history/workflow · GitHub | docs · glossary |
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| Payload / Payload Converter / Payload Codec / Data Converter | The wire representation of values and the SDK-side serialization and encoding pipeline. | | docs · glossary |
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| Persistence store | The pluggable database (Cassandra, MySQL, Postgres, SQLite) that is the source of truth for shards, executions, history, tasks, and metadata. | | docs · glossary |
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| Query | A synchronous read answered by a worker from cached state; dispatched through the sticky queue or attached to the next Workflow Task. | service/history/api/queryworkflow · GitHub service/history/workflow · GitHub service/matching · GitHub | docs · glossary |
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| Queue processor | The per-shard loop that reads a task category from its ack level, schedules, retries, and dead-letters tasks. | | docs · glossary |
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| RangeID | The per-shard fencing token: a host claims a shard by compare-and-swapping it and every write carries it. | | docs · glossary |
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| Replication Lag | The delay between active and standby clusters, tracked by the replication streams. | service/history/replication · GitHub | docs · glossary |
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| Requests Per Second (RPS) | Service-level and namespace-level rate limits applied in Frontend interceptors and persistence clients. | | docs · glossary |
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| Reset | Terminates an execution and starts a new run from a chosen history point by forking a history branch. | service/history/api/resetworkflow · GitHub service/history/ndc · GitHub service/history/api/reapplyevents · GitHub | docs · glossary |
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| Retention Period | How long a closed execution's history stays in persistence before a cleanup timer deletes it. | service/history/deletemanager · GitHub service/history/queues · GitHub service/history/workflow · GitHub | docs · glossary |
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| Retry Policy | Server-side retry attributes for Activities and Workflows; activity retries go straight back to Matching via a retry timer. | | docs · glossary |
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| Ringpop | Gossip membership plus a consistent hash ring per service, used to find which host owns a shard or partition. | | docs · glossary |
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| Run ID | A platform-generated ID for one run of a Workflow ID; new runs come from continue-as-new, retry, cron, and reset. | service/history/api/startworkflow · GitHub service/history/workflow · GitHub | docs · glossary |
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| Schedule | A first-class resource that starts executions on a spec, with pause, backfill, and overlap policies; V1 is a system workflow, V2 is CHASM. | service/worker/scheduler · GitHub chasm/lib/scheduler · GitHub service/worker/scanner/scheduleinvariants · GitHub api/schedule/v1 · GitHub | docs · glossary |
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| Search Attribute | An indexed key usable in List Filters, set at start or upserted from workflow code. | | docs · glossary |
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| Shard controller | Watches cluster membership and acquires or releases the shards a History host should own. | service/history/shard · GitHub | docs · glossary |
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| Side Effect | A short non-deterministic snippet whose result is recorded as a marker Event. | sdk · SDK repositories service/history/workflow · GitHub | docs · glossary |
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| Signal | An asynchronous message to a running execution, written as an Event and triggering a Workflow Task. | service/history/api/signalworkflow · GitHub service/history/queues · GitHub service/history/api/removesignalmutablestate · GitHub | docs · glossary |
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| Signal-With-Start | Atomically start an execution if absent, then deliver a Signal. | service/history/api/signalwithstartworkflow · GitHub service/history/api/multioperation · GitHub | docs · glossary |
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| Speculative Workflow Task | A Workflow Task that is never persisted, so a rejected Update costs zero writes; its timeout runs on an in-memory queue. | service/history/workflow · GitHub service/history/queues · GitHub | docs · glossary |
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| Standalone Activity | An Activity started directly from a client with no enclosing workflow, implemented as a CHASM archetype. | | docs · glossary |
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| State Transition | One unit of progress of an execution, counted in the transition history that acts as a logical clock. | | docs · glossary |
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| Sticky Execution | Routing follow-up Workflow Tasks to a worker-private queue so cached state is reused instead of replayed. | service/matching · GitHub service/history/api/resetstickytaskqueue · GitHub common/tqid · diagram · GitHub sdk · SDK repositories | docs · glossary |
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| Sync match | Matching handing a task directly to a parked long-poller without writing the backlog. | | docs · glossary |
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| System workflows | Temporal workflows the Worker service runs against the server itself. | service/worker/scanner · GitHub service/worker/batcher · GitHub service/worker/deletenamespace · GitHub service/worker/parentclosepolicy · GitHub service/worker/addsearchattributes · GitHub common/sdk · diagram · GitHub | docs · glossary |
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| Tag | A key-value label on an emitted metric. | | docs · glossary |
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| Task Queue | A dynamically created FIFO queue workers poll; the routing key between server and workers. | | docs · glossary |
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| Task queue partition | One of N physical sub-queues of a Task Queue, arranged as a tree with forwarding to the root; load balanced by the Matching client. | | docs · glossary |
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| Task Routing | Using distinct Task Queues to send specific Activities to specific workers. | service/matching · GitHub sdk · SDK repositories | docs · glossary |
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| Task Token | An opaque identifier for one Activity Task Execution used for async completion and heartbeats. | | docs · glossary |
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| Temporal CLI / tctl | The user CLI lives in a separate repository; tdbg is the in-repo admin debugging tool. | | docs · glossary |
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| Temporal Cron Job | Legacy cron by chaining runs under one Workflow ID with a backoff timer between them. | service/history/workflow · GitHub service/history/queues · GitHub | docs · glossary |
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| Temporal SDK / Core SDK / Temporal Client | Language libraries providing the Client and Worker, with a shared Rust core for several languages. | | docs · glossary |
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| Temporal Server | The four horizontally scalable services (Frontend, History, Matching, Worker) composed with Uber fx and started from one binary. | | docs · glossary |
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| Temporal Service configuration | The static YAML configuration for persistence, services, membership, TLS, and archival. | | docs · glossary |
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| Timer | Durable workflow time APIs; the server fires user timers from the per-shard timer queue even with no worker running. | | docs · glossary |
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| Transfer / timer / visibility / outbound / replication tasks | Task categories written in the same transaction as mutable state and executed by per-shard queue processors. | service/history/tasks · GitHub service/history/queues · GitHub service/history/workflow · GitHub | docs · glossary |
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| Transient Workflow Task | A retried Workflow Task whose scheduled and started events are withheld until completion. | service/history/workflow · GitHub | docs · glossary |
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| Update | A synchronous request-and-response that may mutate state, with validation, accepted, and completed phases. | service/history/workflow/update · GitHub service/history/api/updateworkflow · GitHub service/history/api/pollupdate · GitHub common/protocol · diagram · GitHub | docs · glossary |
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| Versioned transition | The (failover version, transition count) logical clock for mutable state and CHASM. | | docs · glossary |
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| Visibility | Listing, counting, and searching executions through an eventually consistent store written by the visibility queue. | | docs · glossary |
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| Worker / Worker Process / Worker Entity / Worker Program | The user-run process that polls Task Queues, executes code, and responds to the server. | sdk · SDK repositories service/matching/workers · GitHub common/workercommands · diagram · GitHub | docs · glossary |
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| Worker Service | Runs system workflows and background jobs (scanner, batcher, schedules V1, worker deployments, migrations) against the Frontend. | | docs · glossary |
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| Worker Session | Go SDK feature running a sequence of Activities on one worker via a host-specific Task Queue. | sdk · SDK repositories
| docs · glossary |
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| Worker Versioning / Worker Deployment / Build ID | Routing Workflow Tasks only to workers running compatible code; PINNED keeps an execution on its starting version. | | docs · glossary |
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| Workflow cache | The worker-side cache of executions backing Sticky Execution. | sdk · SDK repositories
| docs · glossary |
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| Workflow Definition | Deterministic user code that defines a workflow; replayed by the SDK against history. | sdk · SDK repositories
| docs · glossary |
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| Workflow Execution | One durable run of a Workflow Definition, identified by Workflow ID plus Run ID, with its own Event History. | service/history/workflow · GitHub service/history/api/startworkflow · GitHub service/history/api/describeworkflow · GitHub service/history/api/terminateworkflow · GitHub | docs · glossary |
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| Workflow Execution Timeout | Max total time for a Workflow ID across all runs. | service/history/queues · GitHub service/history/workflow · GitHub | docs · glossary |
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| Workflow ID | A user-chosen identifier; at most one open execution per ID per namespace, enforced through the current-execution record. | | docs · glossary |
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| Workflow ID Conflict Policy | What to do when starting a Workflow ID that is currently running: fail, use existing, or terminate existing. | service/history/api/startworkflow · GitHub service/history/api/multioperation · GitHub | docs · glossary |
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| Workflow ID Reuse Policy | Whether a new execution may reuse a Workflow ID from a closed execution. | service/history/api/startworkflow · GitHub | docs · glossary |
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| Workflow Run Timeout | Max time for one run. | service/history/queues · GitHub service/history/workflow · GitHub | docs · glossary |
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| Workflow Task | A task telling a worker to advance an execution; History schedules it, Matching dispatches it, the worker replays and returns Commands. | service/history/workflow · GitHub service/history/api/scheduleworkflowtask · GitHub service/history/api/recordworkflowtaskstarted · GitHub service/history/api/respondworkflowtaskcompleted · GitHub service/history/api/respondworkflowtaskfailed · GitHub service/matching · GitHub | docs · glossary |
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| Workflow Task Timeout | How long the server waits for a worker to start a Workflow Task before rescheduling it. | service/history/queues · GitHub service/history/workflow · GitHub | docs · glossary |
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