Extension: BranchRetryParallel State

The BranchRetryParallel class extends the Parallel state.

Parallel supports retrying the state if one or more of its branches generates an error that is included in the Retrier list. This class extends this behaviour, allowing the branches to define errors that can be retried before the whole state is retried.

This extension can ensure that an intermittent failure on a single branch does not trigger significant unnecessary reprocessing of the successful branches.

For more details on Parallel, see the AWS documentation.

class awssl.ext.BranchRetryParallel(Name=None, Comment='', InputPath='$', OutputPath='$', NextState=None, EndState=None, ResultPath='$', RetryList=None, CatcherList=None, BranchList=None, BranchRetryList=None)

Extends the Parallel state, providing optional retries on each branch separately.

Either:

  • EndState is True and NextState must be None
  • EndState is False and NextState must be a valid instance of a class derived from StateBase.

Output is returned as a list of the outputs from each branch, as with Parallel.

Parameters:
  • Name (str) – [Required] The name of the state within the branch of the state machine
  • Comment (str) – [Optional] A comment describing the intent of this pass state
  • InputPath (str) – [Optional] Filter on the Input information to be passed to the Pass state. Default is “$”, signifying that all the Input information will be provided
  • OutputPath (str) – [Optional] Filter on the Output information to be returned from the Pass state. Default is “$”, signifying that all the result information will be provided
  • EndState (bool) – [Optional] Flag indicating if this state terminates a branch of the state machine. Defaults to False
  • NextState (instance of class derived from StateBase) – [Optional] Next state to be invoked within this branch. Must not be None unless EndState is True
  • ResultPath (str) – [Optional] JSONPath indicating where results should be added to the Input. Defaults to “$”, indicating results replace the Input entirely.
  • RetryList – [Optional] list of Retrier instances corresponding to error states that cause the entire set of branches to be retried
  • CatcherList – [Optional] list of Catcher instances corresponding to error states that can be caught and handled by further states being executed in the StateMachine.
  • BranchList – [Required] list of StateBase instances, providing the starting states for each branch to be run concurrently
  • BranchRetryList – [Optional] list of Retrier instances corresponding to error states that can be retried for each branch
Type:

RetryList: list of Retrier
Type:

CatcherList: list of Catcher
Type:

BranchList: list of StateBase
Type:

BranchRetryList: list of StateBase
clone(NameFormatString='{}')

Returns a clone of this instance, with the clone named per the NameFormatString, to avoid state name clashes.

If this instance is not an end state, then the next state will also be cloned, to establish a complete clone of the branch form this instance onwards.

Parameters:NameFormatString (str) – [Required] The naming template to be applied to generate the name of the new instance.
Returns:BranchRetryParallel – A new instance of this instance and any other instances in its branch.
get_branch_list()

Returns the list of starting states for each branch to be executed concurrently

Returns:list of StateBase instances
get_branch_retry_list()

Returns the list of Retrier instances that will be applied to each branch separately, allowing failure in one branch to be retried without having to re-execute all the branches of the Parallel.

Returns:list of Retrier instances
set_branch_list(BranchList=None)

Sets the list of starting states for each branch to be executed concurrently.

At least one branch is required for the state to be valid.

Parameters:BranchList – [Required] list of StateBase instances, providing the starting states for each branch to be run concurrently
Type:BranchList: list of StateBase
set_branch_retry_list(BranchRetryList=None)

Sets the list of Retrier instance to be applied to the branches in the Parallel.

If none are set, then the behaviour of this state is equivalent to the Parallel state.

Parameters:BranchRetryList – [Optional] list of Retrier instances corresponding to error states that can be retried for each branch
Type:BranchRetryList: list of StateBase
to_json()

Returns the JSON representation of this instance.

Returns:dict – The JSON representation
validate()

Validates this instance is correctly specified.

Raises Exception with details of the error, if the state machine is incorrectly defined.