Execution states

The state transitions of an execution can be represented in a diagram:

When an execution is first scheduled, it starts in the Queued state (unless caching is enabled and there is a cache hit, in which case it transitions straight to Cached).

From the Queued state it will transition to Assigned once it is due, and a suitable agent is available to run it, unless it become 'deferred' by another execution in the meantime.

Once assigned, the agent will generally execute it until it succeeds (Succeeded) or raises an exception (Failed). If contact is lost with an agent for more than the timeout period, the task that are running will be marked as Abandoned (we don't know whether it completed successfully). Executions may be Cancelled while they're running (or before they've been assigned). An execution may choose to suspend itself (either explicitly, or from timing out while waiting for another execution to complete) - in this case it will be automatically re-run.

Steps maybe be configured to automatically retry (from a failed or abandoned state), or they may be re-run manually, in which case a new execution will be started.