update-state
============

Updates the dynamoDB state database with the State Function execution
results.

Completion of a State Function execution can also be used to chain
additional workflow steps with pushing messages to SQS or SNS for
additional steps beyond the core cirrus workflow, like triggering a
lambda to push an output STAC Item to a STAC API.

Trigger
-------

The ``update-state`` lambda listens for terminal events output by a
State Function that is executing a cirrus workflow/task. These terminal
states are not an exclusive list of possible states in the StateDB.

- “SUCCEEDED”: the successful completion of a cirrus workflow
- “FAILED”: A failed execution. This can occur for a variety of reasons
- “ABORTED”: The state machinea was forced to abort execution. Can be
  triggered by manual termination of a workflow.
- “TIMED OUT”: State machine terminated due to time out. Can occur if a
  third party resource involved in a task hangs, or a workflow
  configuration did not allow sufficient time for a task to complete.

StateDB Updates
---------------

Updating the DynamoDB state database is the core functionality of the
``update-state`` lambda.

In addition to updating DynamoDB the ``update-state`` lambda also fires
off events to AWS TimeStream with each state update.

The ``update-state`` lambda additionally logs any errors that come from
the StateMachine so they can be captured and anlyzed in the log stream.

``update-state`` can send messages to configured SNS topics to provide
notifications to users or downstream services when events and/or output
items are produced. It may also be used to facilitate workflow chaining
by requeuing payloads in the ``process`` queue.