@aws-cdk/aws-stepfunctions

AWS Step Functions Construct Library

---

---

The @aws-cdk/aws-stepfunctions package contains constructs for building serverless workflows using objects. Use this in conjunction with the @aws-cdk/aws-stepfunctions-tasks package, which contains classes used to call other AWS services.

Defining a workflow looks like this (for the Step Functions Job Poller example):

Example

import * as lambda from '@aws-cdk/aws-lambda';

declare const submitLambda: lambda.Function;
declare const getStatusLambda: lambda.Function;

const submitJob = new tasks.LambdaInvoke(this, 'Submit Job', {
  lambdaFunction: submitLambda,
  // Lambda's result is in the attribute `Payload`
  outputPath: '$.Payload',
});

const waitX = new sfn.Wait(this, 'Wait X Seconds', {
  time: sfn.WaitTime.secondsPath('$.waitSeconds'),
});

const getStatus = new tasks.LambdaInvoke(this, 'Get Job Status', {
  lambdaFunction: getStatusLambda,
  // Pass just the field named "guid" into the Lambda, put the
  // Lambda's result in a field called "status" in the response
  inputPath: '$.guid',
  outputPath: '$.Payload',
});

const jobFailed = new sfn.Fail(this, 'Job Failed', {
  cause: 'AWS Batch Job Failed',
  error: 'DescribeJob returned FAILED',
});

const finalStatus = new tasks.LambdaInvoke(this, 'Get Final Job Status', {
  lambdaFunction: getStatusLambda,
  // Use "guid" field as input
  inputPath: '$.guid',
  outputPath: '$.Payload',
});

const definition = submitJob
  .next(waitX)
  .next(getStatus)
  .next(new sfn.Choice(this, 'Job Complete?')
    // Look at the "status" field
    .when(sfn.Condition.stringEquals('$.status', 'FAILED'), jobFailed)
    .when(sfn.Condition.stringEquals('$.status', 'SUCCEEDED'), finalStatus)
    .otherwise(waitX));

new sfn.StateMachine(this, 'StateMachine', {
  definition,
  timeout: Duration.minutes(5),
});

You can find more sample snippets and learn more about the service integrations in the @aws-cdk/aws-stepfunctions-tasks package.

State Machine

A stepfunctions.StateMachine is a resource that takes a state machine definition. The definition is specified by its start state, and encompasses all states reachable from the start state:

const startState = new sfn.Pass(this, 'StartState');

new sfn.StateMachine(this, 'StateMachine', {
  definition: startState,
});

State machines execute using an IAM Role, which will automatically have all permissions added that are required to make all state machine tasks execute properly (for example, permissions to invoke any Lambda functions you add to your workflow). A role will be created by default, but you can supply an existing one as well.

Accessing State (the JsonPath class)

Every State Machine execution has State Machine Data: a JSON document containing keys and values that is fed into the state machine, gets modified as the state machine progresses, and finally is produced as output.

You can pass fragments of this State Machine Data into Tasks of the state machine. To do so, use the static methods on the JsonPath class. For example, to pass the value that's in the data key of OrderId to a Lambda function as you invoke it, use JsonPath.stringAt('$.OrderId'), like so:

import * as lambda from '@aws-cdk/aws-lambda';

declare const orderFn: lambda.Function;

const submitJob = new tasks.LambdaInvoke(this, 'InvokeOrderProcessor', {
  lambdaFunction: orderFn,
  payload: sfn.TaskInput.fromObject({
    OrderId: sfn.JsonPath.stringAt('$.OrderId'),
  }),
});

The following methods are available:

Method	Purpose
JsonPath.stringAt('$.Field')	reference a field, return the type as a string.
JsonPath.listAt('$.Field')	reference a field, return the type as a list of strings.
JsonPath.numberAt('$.Field')	reference a field, return the type as a number. Use this for functions that expect a number argument.
JsonPath.objectAt('$.Field')	reference a field, return the type as an IResolvable. Use this for functions that expect an object argument.
JsonPath.entirePayload	reference the entire data object (equivalent to a path of $).
JsonPath.taskToken	reference the Task Token, used for integration patterns that need to run for a long time.

You can also call intrinsic functions using the methods on JsonPath:

Method	Purpose
JsonPath.array(JsonPath.stringAt('$.Field'), ...)	make an array from other elements.
JsonPath.format('The value is {}.', JsonPath.stringAt('$.Value'))	insert elements into a format string.
JsonPath.stringToJson(JsonPath.stringAt('$.ObjStr'))	parse a JSON string to an object
JsonPath.jsonToString(JsonPath.objectAt('$.Obj'))	stringify an object to a JSON string

Amazon States Language

This library comes with a set of classes that model the Amazon States Language. The following State classes are supported:

• Task
• Pass
• Wait
• Choice
• Parallel
• Succeed
• Fail
• Map
• Custom State

An arbitrary JSON object (specified at execution start) is passed from state to state and transformed during the execution of the workflow. For more information, see the States Language spec.

Task

A Task represents some work that needs to be done. The exact work to be done is determine by a class that implements IStepFunctionsTask, a collection of which can be found in the @aws-cdk/aws-stepfunctions-tasks module.

The tasks in the @aws-cdk/aws-stepfunctions-tasks module support the service integration pattern that integrates Step Functions with services directly in the Amazon States language.

Pass

A Pass state passes its input to its output, without performing work. Pass states are useful when constructing and debugging state machines.

The following example injects some fixed data into the state machine through the result field. The result field will be added to the input and the result will be passed as the state's output.

// Makes the current JSON state { ..., "subObject": { "hello": "world" } }
const pass = new sfn.Pass(this, 'Add Hello World', {
  result: sfn.Result.fromObject({ hello: 'world' }),
  resultPath: '$.subObject',
});

// Set the next state
const nextState = new sfn.Pass(this, 'NextState');
pass.next(nextState);

The Pass state also supports passing key-value pairs as input. Values can be static, or selected from the input with a path.

The following example filters the greeting field from the state input and also injects a field called otherData.

const pass = new sfn.Pass(this, 'Filter input and inject data', {
  parameters: { // input to the pass state
    input: sfn.JsonPath.stringAt('$.input.greeting'),
    otherData: 'some-extra-stuff',
  },
});

The object specified in parameters will be the input of the Pass state. Since neither Result nor ResultPath are supplied, the Pass state copies its input through to its output.

Learn more about the Pass state

Wait

A Wait state waits for a given number of seconds, or until the current time hits a particular time. The time to wait may be taken from the execution's JSON state.

// Wait until it's the time mentioned in the the state object's "triggerTime"
// field.
const wait = new sfn.Wait(this, 'Wait For Trigger Time', {
  time: sfn.WaitTime.timestampPath('$.triggerTime'),
});

// Set the next state
const startTheWork = new sfn.Pass(this, 'StartTheWork');
wait.next(startTheWork);

Choice

A Choice state can take a different path through the workflow based on the values in the execution's JSON state:

const choice = new sfn.Choice(this, 'Did it work?');

// Add conditions with .when()
const successState = new sfn.Pass(this, 'SuccessState');
const failureState = new sfn.Pass(this, 'FailureState');
choice.when(sfn.Condition.stringEquals('$.status', 'SUCCESS'), successState);
choice.when(sfn.Condition.numberGreaterThan('$.attempts', 5), failureState);

// Use .otherwise() to indicate what should be done if none of the conditions match
const tryAgainState = new sfn.Pass(this, 'TryAgainState');
choice.otherwise(tryAgainState);

If you want to temporarily branch your workflow based on a condition, but have all branches come together and continuing as one (similar to how an if ... then ... else works in a programming language), use the .afterwards() method:

const choice = new sfn.Choice(this, 'What color is it?');
const handleBlueItem = new sfn.Pass(this, 'HandleBlueItem');
const handleRedItem = new sfn.Pass(this, 'HandleRedItem');
const handleOtherItemColor = new sfn.Pass(this, 'HanldeOtherItemColor');
choice.when(sfn.Condition.stringEquals('$.color', 'BLUE'), handleBlueItem);
choice.when(sfn.Condition.stringEquals('$.color', 'RED'), handleRedItem);
choice.otherwise(handleOtherItemColor);

// Use .afterwards() to join all possible paths back together and continue
const shipTheItem = new sfn.Pass(this, 'ShipTheItem');
choice.afterwards().next(shipTheItem);

If your Choice doesn't have an otherwise() and none of the conditions match the JSON state, a NoChoiceMatched error will be thrown. Wrap the state machine in a Parallel state if you want to catch and recover from this.

Available Conditions

see step function comparison operators

• Condition.isPresent - matches if a json path is present
• Condition.isNotPresent - matches if a json path is not present
• Condition.isString - matches if a json path contains a string
• Condition.isNotString - matches if a json path is not a string
• Condition.isNumeric - matches if a json path is numeric
• Condition.isNotNumeric - matches if a json path is not numeric
• Condition.isBoolean - matches if a json path is boolean
• Condition.isNotBoolean - matches if a json path is not boolean
• Condition.isTimestamp - matches if a json path is a timestamp
• Condition.isNotTimestamp - matches if a json path is not a timestamp
• Condition.isNotNull - matches if a json path is not null
• Condition.isNull - matches if a json path is null
• Condition.booleanEquals - matches if a boolean field has a given value
• Condition.booleanEqualsJsonPath - matches if a boolean field equals a value in a given mapping path
• Condition.stringEqualsJsonPath - matches if a string field equals a given mapping path
• Condition.stringEquals - matches if a field equals a string value
• Condition.stringLessThan - matches if a string field sorts before a given value
• Condition.stringLessThanJsonPath - matches if a string field sorts before a value at given mapping path
• Condition.stringLessThanEquals - matches if a string field sorts equal to or before a given value
• Condition.stringLessThanEqualsJsonPath - matches if a string field sorts equal to or before a given mapping
• Condition.stringGreaterThan - matches if a string field sorts after a given value
• Condition.stringGreaterThanJsonPath - matches if a string field sorts after a value at a given mapping path
• Condition.stringGreaterThanEqualsJsonPath - matches if a string field sorts after or equal to value at a given mapping path
• Condition.stringGreaterThanEquals - matches if a string field sorts after or equal to a given value
• Condition.numberEquals - matches if a numeric field has the given value
• Condition.numberEqualsJsonPath - matches if a numeric field has the value in a given mapping path
• Condition.numberLessThan - matches if a numeric field is less than the given value
• Condition.numberLessThanJsonPath - matches if a numeric field is less than the value at the given mapping path
• Condition.numberLessThanEquals - matches if a numeric field is less than or equal to the given value
• Condition.numberLessThanEqualsJsonPath - matches if a numeric field is less than or equal to the numeric value at given mapping path
• Condition.numberGreaterThan - matches if a numeric field is greater than the given value
• Condition.numberGreaterThanJsonPath - matches if a numeric field is greater than the value at a given mapping path
• Condition.numberGreaterThanEquals - matches if a numeric field is greater than or equal to the given value
• Condition.numberGreaterThanEqualsJsonPath - matches if a numeric field is greater than or equal to the value at a given mapping path
• Condition.timestampEquals - matches if a timestamp field is the same time as the given timestamp
• Condition.timestampEqualsJsonPath - matches if a timestamp field is the same time as the timestamp at a given mapping path
• Condition.timestampLessThan - matches if a timestamp field is before the given timestamp
• Condition.timestampLessThanJsonPath - matches if a timestamp field is before the timestamp at a given mapping path
• Condition.timestampLessThanEquals - matches if a timestamp field is before or equal to the given timestamp
• Condition.timestampLessThanEqualsJsonPath - matches if a timestamp field is before or equal to the timestamp at a given mapping path
• Condition.timestampGreaterThan - matches if a timestamp field is after the timestamp at a given mapping path
• Condition.timestampGreaterThanJsonPath - matches if a timestamp field is after the timestamp at a given mapping path
• Condition.timestampGreaterThanEquals - matches if a timestamp field is after or equal to the given timestamp
• Condition.timestampGreaterThanEqualsJsonPath - matches if a timestamp field is after or equal to the timestamp at a given mapping path
• Condition.stringMatches - matches if a field matches a string pattern that can contain a wild card (*) e.g: log-*.txt or *LATEST*. No other characters other than "*" have any special meaning - * can be escaped: \\*

Parallel

A Parallel state executes one or more subworkflows in parallel. It can also be used to catch and recover from errors in subworkflows.

const parallel = new sfn.Parallel(this, 'Do the work in parallel');

// Add branches to be executed in parallel
const shipItem = new sfn.Pass(this, 'ShipItem');
const sendInvoice = new sfn.Pass(this, 'SendInvoice');
const restock = new sfn.Pass(this, 'Restock');
parallel.branch(shipItem);
parallel.branch(sendInvoice);
parallel.branch(restock);

// Retry the whole workflow if something goes wrong
parallel.addRetry({ maxAttempts: 1 });

// How to recover from errors
const sendFailureNotification = new sfn.Pass(this, 'SendFailureNotification');
parallel.addCatch(sendFailureNotification);

// What to do in case everything succeeded
const closeOrder = new sfn.Pass(this, 'CloseOrder');
parallel.next(closeOrder);

Succeed

Reaching a Succeed state terminates the state machine execution with a successful status.

const success = new sfn.Succeed(this, 'We did it!');

Fail

Reaching a Fail state terminates the state machine execution with a failure status. The fail state should report the reason for the failure. Failures can be caught by encompassing Parallel states.

const success = new sfn.Fail(this, 'Fail', {
  error: 'WorkflowFailure',
  cause: "Something went wrong",
});

Map

A Map state can be used to run a set of steps for each element of an input array. A Map state will execute the same steps for multiple entries of an array in the state input.

While the Parallel state executes multiple branches of steps using the same input, a Map state will execute the same steps for multiple entries of an array in the state input.

const map = new sfn.Map(this, 'Map State', {
  maxConcurrency: 1,
  itemsPath: sfn.JsonPath.stringAt('$.inputForMap'),
});
map.iterator(new sfn.Pass(this, 'Pass State'));

Custom State

It's possible that the high-level constructs for the states or stepfunctions-tasks do not have the states or service integrations you are looking for. The primary reasons for this lack of functionality are:

• A service integration is available through Amazon States Langauge, but not available as construct classes in the CDK.
• The state or state properties are available through Step Functions, but are not configurable through constructs

If a feature is not available, a CustomState can be used to supply any Amazon States Language JSON-based object as the state definition.

Code Snippets are available and can be plugged in as the state definition.

Custom states can be chained together with any of the other states to create your state machine definition. You will also need to provide any permissions that are required to the role that the State Machine uses.

The following example uses the DynamoDB service integration to insert data into a DynamoDB table.

import * as dynamodb from '@aws-cdk/aws-dynamodb';

// create a table
const table = new dynamodb.Table(this, 'montable', {
  partitionKey: {
    name: 'id',
    type: dynamodb.AttributeType.STRING,
  },
});

const finalStatus = new sfn.Pass(this, '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
const stateJson = {
  Type: 'Task',
  Resource: 'arn:aws:states:::dynamodb:putItem',
  Parameters: {
    TableName: table.tableName,
    Item: {
      id: {
        S: 'MyEntry',
      },
    },
  },
  ResultPath: null,
};

// custom state which represents a task to insert data into DynamoDB
const custom = new sfn.CustomState(this, 'my custom task', {
  stateJson,
});

const chain = sfn.Chain.start(custom)
  .next(finalStatus);

const sm = new sfn.StateMachine(this, 'StateMachine', {
  definition: chain,
  timeout: Duration.seconds(30),
});

// don't forget permissions. You need to assign them
table.grantWriteData(sm);

Task Chaining

To make defining work flows as convenient (and readable in a top-to-bottom way) as writing regular programs, it is possible to chain most methods invocations. In particular, the .next() method can be repeated. The result of a series of .next() calls is called a Chain, and can be used when defining the jump targets of Choice.on or Parallel.branch:

const step1 = new sfn.Pass(this, 'Step1');
const step2 = new sfn.Pass(this, 'Step2');
const step3 = new sfn.Pass(this, 'Step3');
const step4 = new sfn.Pass(this, 'Step4');
const step5 = new sfn.Pass(this, 'Step5');
const step6 = new sfn.Pass(this, 'Step6');
const step7 = new sfn.Pass(this, 'Step7');
const step8 = new sfn.Pass(this, 'Step8');
const step9 = new sfn.Pass(this, 'Step9');
const step10 = new sfn.Pass(this, 'Step10');
const choice = new sfn.Choice(this, 'Choice');
const condition1 = sfn.Condition.stringEquals('$.status', 'SUCCESS');
const parallel = new sfn.Parallel(this, 'Parallel');
const finish = new sfn.Pass(this, 'Finish');

const definition = step1
  .next(step2)
  .next(choice
    .when(condition1, step3.next(step4).next(step5))
    .otherwise(step6)
    .afterwards())
  .next(parallel
    .branch(step7.next(step8))
    .branch(step9.next(step10)))
  .next(finish);

new sfn.StateMachine(this, 'StateMachine', {
  definition,
});

If you don't like the visual look of starting a chain directly off the first step, you can use Chain.start:

const step1 = new sfn.Pass(this, 'Step1');
const step2 = new sfn.Pass(this, 'Step2');
const step3 = new sfn.Pass(this, 'Step3');

const definition = sfn.Chain
  .start(step1)
  .next(step2)
  .next(step3)
  // ...

State Machine Fragments

It is possible to define reusable (or abstracted) mini-state machines by defining a construct that implements IChainable, which requires you to define two fields:

• startState: State, representing the entry point into this state machine.
• endStates: INextable[], representing the (one or more) states that outgoing transitions will be added to if you chain onto the fragment.

Since states will be named after their construct IDs, you may need to prefix the IDs of states if you plan to instantiate the same state machine fragment multiples times (otherwise all states in every instantiation would have the same name).

The class StateMachineFragment contains some helper functions (like prefixStates()) to make it easier for you to do this. If you define your state machine as a subclass of this, it will be convenient to use:

import { Stack } from '@aws-cdk/core';
import { Construct } from 'constructs';
import * as sfn from '@aws-cdk/aws-stepfunctions';

interface MyJobProps {
  jobFlavor: string;
}

class MyJob extends sfn.StateMachineFragment {
  public readonly startState: sfn.State;
  public readonly endStates: sfn.INextable[];

  constructor(parent: Construct, id: string, props: MyJobProps) {
    super(parent, id);

    const choice = new sfn.Choice(this, 'Choice')
      .when(sfn.Condition.stringEquals('$.branch', 'left'), new sfn.Pass(this, 'Left Branch'))
      .when(sfn.Condition.stringEquals('$.branch', 'right'), new sfn.Pass(this, 'Right Branch'));

    // ...

    this.startState = choice;
    this.endStates = choice.afterwards().endStates;
  }
}

class MyStack extends Stack {
  constructor(scope: Construct, id: string) {
    super(scope, id);
    // Do 3 different variants of MyJob in parallel
    const parallel = new sfn.Parallel(this, 'All jobs')
      .branch(new MyJob(this, 'Quick', { jobFlavor: 'quick' }).prefixStates())
      .branch(new MyJob(this, 'Medium', { jobFlavor: 'medium' }).prefixStates())
      .branch(new MyJob(this, 'Slow', { jobFlavor: 'slow' }).prefixStates());

    new sfn.StateMachine(this, 'MyStateMachine', {
      definition: parallel,
    });
  }
}

A few utility functions are available to parse state machine fragments.

• State.findReachableStates: Retrieve the list of states reachable from a given state.
• State.findReachableEndStates: Retrieve the list of end or terminal states reachable from a given state.

Activity

Activities represent work that is done on some non-Lambda worker pool. The Step Functions workflow will submit work to this Activity, and a worker pool that you run yourself, probably on EC2, will pull jobs from the Activity and submit the results of individual jobs back.

You need the ARN to do so, so if you use Activities be sure to pass the Activity ARN into your worker pool:

const activity = new sfn.Activity(this, 'Activity');

// Read this CloudFormation Output from your application and use it to poll for work on
// the activity.
new CfnOutput(this, 'ActivityArn', { value: activity.activityArn });

Activity-Level Permissions

Granting IAM permissions to an activity can be achieved by calling the grant(principal, actions) API:

const activity = new sfn.Activity(this, 'Activity');

const role = new iam.Role(this, 'Role', {
  assumedBy: new iam.ServicePrincipal('lambda.amazonaws.com'),
});

activity.grant(role, 'states:SendTaskSuccess');

This will grant the IAM principal the specified actions onto the activity.

Metrics

Task object expose various metrics on the execution of that particular task. For example, to create an alarm on a particular task failing:

declare const task: sfn.Task;
new cloudwatch.Alarm(this, 'TaskAlarm', {
  metric: task.metricFailed(),
  threshold: 1,
  evaluationPeriods: 1,
});

There are also metrics on the complete state machine:

declare const stateMachine: sfn.StateMachine;
new cloudwatch.Alarm(this, 'StateMachineAlarm', {
  metric: stateMachine.metricFailed(),
  threshold: 1,
  evaluationPeriods: 1,
});

And there are metrics on the capacity of all state machines in your account:

new cloudwatch.Alarm(this, 'ThrottledAlarm', {
  metric: sfn.StateTransitionMetric.metricThrottledEvents(),
  threshold: 10,
  evaluationPeriods: 2,
});

Error names

Step Functions identifies errors in the Amazon States Language using case-sensitive strings, known as error names. The Amazon States Language defines a set of built-in strings that name well-known errors, all beginning with the States. prefix.

• States.ALL - A wildcard that matches any known error name.
• States.Runtime - An execution failed due to some exception that could not be processed. Often these are caused by errors at runtime, such as attempting to apply InputPath or OutputPath on a null JSON payload. A States.Runtime error is not retriable, and will always cause the execution to fail. A retry or catch on States.ALL will NOT catch States.Runtime errors.
• States.DataLimitExceeded - A States.DataLimitExceeded exception will be thrown for the following:
  • When the output of a connector is larger than payload size quota.
  • When the output of a state is larger than payload size quota.
  • When, after Parameters processing, the input of a state is larger than the payload size quota.
  • See the AWS documentation to learn more about AWS Step Functions Quotas.
• States.HeartbeatTimeout - A Task state failed to send a heartbeat for a period longer than the HeartbeatSeconds value.
• States.Timeout - A Task state either ran longer than the TimeoutSeconds value, or failed to send a heartbeat for a period longer than the HeartbeatSeconds value.
• States.TaskFailed- A Task state failed during the execution. When used in a retry or catch, States.TaskFailed acts as a wildcard that matches any known error name except for States.Timeout.

Logging

Enable logging to CloudWatch by passing a logging configuration with a destination LogGroup:

import * as logs from '@aws-cdk/aws-logs';

const logGroup = new logs.LogGroup(this, 'MyLogGroup');

new sfn.StateMachine(this, 'MyStateMachine', {
  definition: sfn.Chain.start(new sfn.Pass(this, 'Pass')),
  logs: {
    destination: logGroup,
    level: sfn.LogLevel.ALL,
  },
});

X-Ray tracing

Enable X-Ray tracing for StateMachine:

new sfn.StateMachine(this, 'MyStateMachine', {
  definition: sfn.Chain.start(new sfn.Pass(this, 'Pass')),
  tracingEnabled: true,
});

See the AWS documentation to learn more about AWS Step Functions's X-Ray support.

State Machine Permission Grants

IAM roles, users, or groups which need to be able to work with a State Machine should be granted IAM permissions.

Any object that implements the IGrantable interface (has an associated principal) can be granted permissions by calling:

• stateMachine.grantStartExecution(principal) - grants the principal the ability to execute the state machine
• stateMachine.grantRead(principal) - grants the principal read access
• stateMachine.grantTaskResponse(principal) - grants the principal the ability to send task tokens to the state machine
• stateMachine.grantExecution(principal, actions) - grants the principal execution-level permissions for the IAM actions specified
• stateMachine.grant(principal, actions) - grants the principal state-machine-level permissions for the IAM actions specified

Start Execution Permission

Grant permission to start an execution of a state machine by calling the grantStartExecution() API.

const role = new iam.Role(this, 'Role', {
  assumedBy: new iam.ServicePrincipal('lambda.amazonaws.com'),
});

declare const definition: sfn.IChainable;
const stateMachine = new sfn.StateMachine(this, 'StateMachine', {
  definition,
});

// Give role permission to start execution of state machine
stateMachine.grantStartExecution(role);

The following permission is provided to a service principal by the grantStartExecution() API:

• states:StartExecution - to state machine

Read Permissions

Grant read access to a state machine by calling the grantRead() API.

const role = new iam.Role(this, 'Role', {
  assumedBy: new iam.ServicePrincipal('lambda.amazonaws.com'),
});

declare const definition: sfn.IChainable;
const stateMachine = new sfn.StateMachine(this, 'StateMachine', {
  definition,
});

// Give role read access to state machine
stateMachine.grantRead(role);

The following read permissions are provided to a service principal by the grantRead() API:

• states:ListExecutions - to state machine
• states:ListStateMachines - to state machine
• states:DescribeExecution - to executions
• states:DescribeStateMachineForExecution - to executions
• states:GetExecutionHistory - to executions
• states:ListActivities - to *
• states:DescribeStateMachine - to *
• states:DescribeActivity - to *

Task Response Permissions

Grant permission to allow task responses to a state machine by calling the grantTaskResponse() API:

const role = new iam.Role(this, 'Role', {
  assumedBy: new iam.ServicePrincipal('lambda.amazonaws.com'),
});

declare const definition: sfn.IChainable;
const stateMachine = new sfn.StateMachine(this, 'StateMachine', {
  definition,
});

// Give role task response permissions to the state machine
stateMachine.grantTaskResponse(role);

The following read permissions are provided to a service principal by the grantRead() API:

• states:SendTaskSuccess - to state machine
• states:SendTaskFailure - to state machine
• states:SendTaskHeartbeat - to state machine

Execution-level Permissions

Grant execution-level permissions to a state machine by calling the grantExecution() API:

const role = new iam.Role(this, 'Role', {
  assumedBy: new iam.ServicePrincipal('lambda.amazonaws.com'),
});

declare const definition: sfn.IChainable;
const stateMachine = new sfn.StateMachine(this, 'StateMachine', {
  definition,
});

// Give role permission to get execution history of ALL executions for the state machine
stateMachine.grantExecution(role, 'states:GetExecutionHistory');

Custom Permissions

You can add any set of permissions to a state machine by calling the grant() API.

const user = new iam.User(this, 'MyUser');

declare const definition: sfn.IChainable;
const stateMachine = new sfn.StateMachine(this, 'StateMachine', {
  definition,
});

//give user permission to send task success to the state machine
stateMachine.grant(user, 'states:SendTaskSuccess');

Import

Any Step Functions state machine that has been created outside the stack can be imported into your CDK stack.

State machines can be imported by their ARN via the StateMachine.fromStateMachineArn() API

const app = new App();
const stack = new Stack(app, 'MyStack');
sfn.StateMachine.fromStateMachineArn(
  stack,
  'ImportedStateMachine',
  'arn:aws:states:us-east-1:123456789012:stateMachine:StateMachine2E01A3A5-N5TJppzoevKQ',
);