Step and Flow close semantics
查看 MarkdownDetailed rules for completion requests, Flow outputs, and Step cancellation. The concept pages explain the model: Flow and Step. For the messages a canceled Step consumed, see Canceled Steps return consumed messages.
Completion requests
GracefulComplete ends its own branch and asks Dex to complete the Flow. As soon as no Step is active, Dex begins to complete the Flow. The request stays in force: a later branch that ends with DeadEnd does not withdraw it.
Until no Step is active, other Steps and RPCs can still start new Steps, and those Steps delay completion too. Once Dex begins to complete the Flow, it starts no new Step. A naturally closing Flow stays RUNNING until its pending Attribute Store writes finish or are discarded, until transactional or locking RPCs admitted earlier finish, and until Dex records the close. WaitForFlow keeps waiting meanwhile. See Requests during Flow close.
Without a pending GracefulComplete, a Flow with no active Step keeps running. An RPC can still start new Steps in it. Dex never closes a Flow because no Step is active. Something else closes it: its Flow timeout, a stop, or a completing decision.
Flow outputs
GracefulComplete and ForceComplete can carry an output. The Flow result lists each output with its Step type and Step execution ID.
Only a COMPLETED Flow keeps these outputs. A Flow that fails, is canceled, is terminated, or times out has no outputs, even after an earlier GracefulComplete carried one. Keep data that must survive a failure in an Attribute.
Step cancellation
A StepDecision or an RPC can cancel active Steps. Dex selects the Steps to cancel after the decision commits. A decision or an RPC never cancels the Steps that it starts itself.
Canceling a Step discards everything its current method has not committed: its Attribute writes, its Channel publications, and its decision. What its earlier methods committed, such as its WaitFor writes, stays.
Cancellation is cooperative. The SDK signals it to the handler. Dex discards the canceled Step's later result, writes, retries, and recovery routes. A handler that ignores the signal keeps running, and its calls to external systems still take effect, even after the Flow has closed.
A Step that a decision or an RPC cancels never takes the Channel messages published in that same commit. See Pending messages.