Joshua Harlow 155326b6e7 Update the state graph builder to use state machine type

To build the state diagrams switch from using a custom
algorithm that builds a state machine in a table to using
our state machine class to build those same machines before
translation into a dot diagram.

This also allows us to use the state machine that already
is being used in the action engine as the source of transitions
to build the dot diagram with.

Change-Id: I4a0d16a3fb7c620c2774b535ab952b5d5006e9e9

2014-09-09 12:09:09 -07:00

5.8 KiB

Raw Blame History

States

Engine

RESUMING - Prepares flow & atoms to be resumed.

SCHEDULING - Schedules and submits atoms to be worked on.

WAITING - Wait for atoms to finish executing.

ANALYZING - Analyzes and processes result/s of atom completion.

SUCCESS - Completed successfully.

FAILURE - Completed unsuccessfully.

REVERTED - Reverting was induced and all atoms were not completed successfully.

SUSPENDED - Suspended while running.

UNDEFINED - Internal state.

GAME_OVER - Internal state.

Flow

PENDING - A flow starts its life in this state.

RUNNING - In this state flow makes a progress, executes and/or reverts its atoms.

SUCCESS - Once all atoms have finished successfully the flow transitions to the SUCCESS state.

REVERTED - The flow transitions to this state when it has been reverted successfully after the failure.

FAILURE - The flow transitions to this state when it can not be reverted after the failure.

SUSPENDING - In the RUNNING state the flow can be suspended. When this happens, flow transitions to the SUSPENDING state immediately. In that state the engine running the flow waits for running atoms to finish (since the engine can not preempt atoms that are active).

SUSPENDED - When no atoms are running and all results received so far are saved, the flow transitions from the SUSPENDING state to SUSPENDED. Also it may go to the SUCCESS state if all atoms were in fact ran, or to the REVERTED state if the flow was reverting and all atoms were reverted while the engine was waiting for running atoms to finish, or to the FAILURE state if atoms were run or reverted and some of them failed.

RESUMING - When the flow is interrupted 'in a hard way' (e.g. server crashed), it can be loaded from storage in any state. If the state is not PENDING (aka, the flow was never ran) or SUCCESS, FAILURE or REVERTED (in which case the flow has already finished), the flow gets set to the RESUMING state for the short time period while it is being loaded from backend storage [a database, a filesystem...] (this transition is not shown on the diagram). When the flow is finally loaded, it goes to the SUSPENDED state.

From the SUCCESS, FAILURE or REVERTED states the flow can be ran again (and thus it goes back into the RUNNING state). One of the possible use cases for this transition is to allow for alteration of a flow or flow details associated with a previously ran flow after the flow has finished, and client code wants to ensure that each atom from this new (potentially updated) flow has its chance to run.

Note

The current code also contains strong checks during each flow state transition using the model described above and raises the :py~taskflow.exceptions.InvalidState exception if an invalid transition is attempted. This exception being triggered usually means there is some kind of bug in the engine code or some type of misuse/state violation is occurring, and should be reported as such.

Task

PENDING - When a task is added to a flow, it starts in the PENDING state, which means it can be executed immediately or waits for all of task it depends on to complete. The task transitions to the PENDING state after it was reverted and its flow was restarted or retried.

RUNNING - When flow starts to execute the task, it transitions to the RUNNING state, and stays in this state until its :pyexecute() <taskflow.task.BaseTask.execute> method returns.

SUCCESS - The task transitions to this state after it was finished successfully.

FAILURE - The task transitions to this state after it was finished with error. When the flow containing this task is being reverted, all its tasks are walked in particular order.

REVERTING - The task transitions to this state when the flow starts to revert it and its :pyrevert() <taskflow.task.BaseTask.revert> method is called. Only tasks in the SUCCESS or FAILURE state can be reverted. If this method fails (raises exception), the task goes to the FAILURE state.

REVERTED - A task that has been reverted appears in this state.

Retry

Retry has the same states as a task and one additional state.

PENDING - When a retry is added to a flow, it starts in the PENDING state, which means it can be executed immediately or waits for all of task it depends on to complete. The retry transitions to the PENDING state after it was reverted and its flow was restarted or retried.

RUNNING - When flow starts to execute the retry, it transitions to the RUNNING state, and stays in this state until its :pyexecute() <taskflow.retry.Retry.execute> method returns.

SUCCESS - The retry transitions to this state after it was finished successfully.

FAILURE - The retry transitions to this state after it was finished with error. When the flow containing this retry is being reverted, all its tasks are walked in particular order.

REVERTING - The retry transitions to this state when the flow starts to revert it and its :pyrevert() <taskflow.retry.Retry.revert> method is called. Only retries in SUCCESS or FAILURE state can be reverted. If this method fails (raises exception), the retry goes to the FAILURE state.

REVERTED - A retry that has been reverted appears in this state.

RETRYING - If flow that is managed by the current retry was failed and reverted, the engine prepares it for the next run and transitions to the RETRYING state.

5.8 KiB Raw Blame History