CustomState

class aws_cdk.aws_stepfunctions.CustomState(scope, id, *, state_json)

Bases: State

State defined by supplying Amazon States Language (ASL) in the state machine.

ExampleMetadata:

infused

Example:

import aws_cdk.aws_dynamodb as dynamodb


# create a table
table = dynamodb.Table(self, "montable",
    partition_key=dynamodb.Attribute(
        name="id",
        type=dynamodb.AttributeType.STRING
    )
)

final_status = sfn.Pass(self, "final step")

# States language JSON to put an item into DynamoDB
# snippet generated from https://docs.aws.amazon.com/step-functions/latest/dg/tutorial-code-snippet.html#tutorial-code-snippet-1
state_json = {
    "Type": "Task",
    "Resource": "arn:aws:states:::dynamodb:putItem",
    "Parameters": {
        "TableName": table.table_name,
        "Item": {
            "id": {
                "S": "MyEntry"
            }
        }
    },
    "ResultPath": null
}

# custom state which represents a task to insert data into DynamoDB
custom = sfn.CustomState(self, "my custom task",
    state_json=state_json
)

# catch errors with addCatch
error_handler = sfn.Pass(self, "handle failure")
custom.add_catch(error_handler)

# retry the task if something goes wrong
custom.add_retry(
    errors=[sfn.Errors.ALL],
    interval=Duration.seconds(10),
    max_attempts=5
)

chain = sfn.Chain.start(custom).next(final_status)

sm = sfn.StateMachine(self, "StateMachine",
    definition_body=sfn.DefinitionBody.from_chainable(chain),
    timeout=Duration.seconds(30),
    comment="a super cool state machine"
)

# don't forget permissions. You need to assign them
table.grant_write_data(sm)
Parameters:

  • scope (Construct) –

  • id (str) – Descriptive identifier for this chainable.

  • state_json (Mapping[str, Any]) – Amazon States Language (JSON-based) definition of the state.

Methods

add_catch(handler, *, assign=None, errors=None, outputs=None, result_path=None)

Add a recovery handler for this state.

When a particular error occurs, execution will continue at the error handler instead of failing the state machine execution.

Parameters:

  • handler (IChainable) –

  • assign (Optional[Mapping[str, Any]]) – Workflow variables to store in this step. Using workflow variables, you can store data in a step and retrieve that data in future steps. Default: - Not assign variables

  • errors (Optional[Sequence[str]]) – Errors to recover from by going to the given state. A list of error strings to retry, which can be either predefined errors (for example Errors.NoChoiceMatched) or a self-defined error. Default: All errors

  • outputs (Any) – This option for JSONata only. When you use JSONPath, then the state ignores this property. Used to specify and transform output from the state. When specified, the value overrides the state output default. The output field accepts any JSON value (object, array, string, number, boolean, null). Any string value, including those inside objects or arrays, will be evaluated as JSONata if surrounded by {% %} characters. Output also accepts a JSONata expression directly. Default: - $states.result or $states.errorOutput

  • result_path (Optional[str]) – JSONPath expression to indicate where to inject the error data. May also be the special value JsonPath.DISCARD, which will cause the error data to be discarded. Default: $

Return type:

CustomState

add_prefix(x)

Add a prefix to the stateId of this state.

Parameters:

x (str) –

Return type:

None

add_retry(*, backoff_rate=None, errors=None, interval=None, jitter_strategy=None, max_attempts=None, max_delay=None)

Add retry configuration for this state.

This controls if and how the execution will be retried if a particular error occurs.

Parameters:

  • backoff_rate (Union[int, float, None]) – Multiplication for how much longer the wait interval gets on every retry. Default: 2

  • errors (Optional[Sequence[str]]) – Errors to retry. A list of error strings to retry, which can be either predefined errors (for example Errors.NoChoiceMatched) or a self-defined error. Default: All errors

  • interval (Optional[Duration]) – How many seconds to wait initially before retrying. Default: Duration.seconds(1)

  • jitter_strategy (Optional[JitterType]) – Introduces a randomization over the retry interval. Default: - No jitter strategy

  • max_attempts (Union[int, float, None]) – How many times to retry this particular error. May be 0 to disable retry for specific errors (in case you have a catch-all retry policy). Default: 3

  • max_delay (Optional[Duration]) – Maximum limit on retry interval growth during exponential backoff. Default: - No max delay

Return type:

CustomState

bind_to_graph(graph)

Register this state as part of the given graph.

Don’t call this. It will be called automatically when you work with states normally.

Parameters:

graph (StateGraph) –

Return type:

None

next(next)

Continue normal execution with the given state.

Parameters:

next (IChainable) –

Return type:

Chain

to_state_json(query_language=None)

Returns the Amazon States Language object for this state.

Parameters:

query_language (Optional[QueryLanguage]) –

Return type:

Mapping[Any, Any]

to_string()

Returns a string representation of this construct.

Return type:

str

Attributes

end_states

Continuable states of this Chainable.

id

Descriptive identifier for this chainable.

node

The tree node.

start_state

First state of this Chainable.

state_id

Tokenized string that evaluates to the state’s ID.

Static Methods

classmethod filter_nextables(states)

Return only the states that allow chaining from an array of states.

Parameters:

states (Sequence[State]) –

Return type:

List[INextable]

classmethod find_reachable_end_states(start, *, include_error_handlers=None)

Find the set of end states states reachable through transitions from the given start state.

Parameters:

  • start (State) –

  • include_error_handlers (Optional[bool]) – Whether or not to follow error-handling transitions. Default: false

Return type:

List[State]

classmethod find_reachable_states(start, *, include_error_handlers=None)

Find the set of states reachable through transitions from the given start state.

This does not retrieve states from within sub-graphs, such as states within a Parallel state’s branch.

Parameters:

  • start (State) –

  • include_error_handlers (Optional[bool]) – Whether or not to follow error-handling transitions. Default: false

Return type:

List[State]

classmethod is_construct(x)

Checks if x is a construct.

Use this method instead of instanceof to properly detect Construct instances, even when the construct library is symlinked.

Explanation: in JavaScript, multiple copies of the constructs library on disk are seen as independent, completely different libraries. As a consequence, the class Construct in each copy of the constructs library is seen as a different class, and an instance of one class will not test as instanceof the other class. npm install will not create installations like this, but users may manually symlink construct libraries together or use a monorepo tool: in those cases, multiple copies of the constructs library can be accidentally installed, and instanceof will behave unpredictably. It is safest to avoid using instanceof, and using this type-testing method instead.

Parameters:

x (Any) – Any object.

Return type:

bool

Returns:

true if x is an object created from a class which extends Construct.

classmethod prefix_states(root, prefix)

Add a prefix to the stateId of all States found in a construct tree.

Parameters:
Return type:

None