StartExecutionCommand

Starts a state machine execution.

A qualified state machine ARN can either refer to a Distributed Map state defined within a state machine, a version ARN, or an alias ARN.

The following are some examples of qualified and unqualified state machine ARNs:

  • The following qualified state machine ARN refers to a Distributed Map state with a label mapStateLabel in a state machine named myStateMachine.

    arn:partition:states:region:account-id:stateMachine:myStateMachine/mapStateLabel

    If you provide a qualified state machine ARN that refers to a Distributed Map state, the request fails with ValidationException.

  • The following qualified state machine ARN refers to an alias named PROD.

    arn::states:::stateMachine:myStateMachine:PROD

    If you provide a qualified state machine ARN that refers to a version ARN or an alias ARN, the request starts execution for that version or alias.

  • The following unqualified state machine ARN refers to a state machine named myStateMachine.

    arn::states:::stateMachine:

If you start an execution with an unqualified state machine ARN, Step Functions uses the latest revision of the state machine for the execution.

To start executions of a state machine version , call StartExecution and provide the version ARN or the ARN of an alias  that points to the version.

StartExecution is idempotent for STANDARD workflows. For a STANDARD workflow, if you call StartExecution with the same name and input as a running execution, the call succeeds and return the same response as the original request. If the execution is closed or if the input is different, it returns a 400 ExecutionAlreadyExists error. You can reuse names after 90 days.

StartExecution isn't idempotent for EXPRESS workflows.

Example Syntax

Use a bare-bones client and the command you need to make an API call.

import { SFNClient, StartExecutionCommand } from "@aws-sdk/client-sfn"; // ES Modules import
// const { SFNClient, StartExecutionCommand } = require("@aws-sdk/client-sfn"); // CommonJS import
const client = new SFNClient(config);
const input = { // StartExecutionInput
  stateMachineArn: "STRING_VALUE", // required
  name: "STRING_VALUE",
  input: "STRING_VALUE",
  traceHeader: "STRING_VALUE",
};
const command = new StartExecutionCommand(input);
const response = await client.send(command);
// { // StartExecutionOutput
//   executionArn: "STRING_VALUE", // required
//   startDate: new Date("TIMESTAMP"), // required
// };

StartExecutionCommand Input

See StartExecutionCommandInput for more details

Parameter
Type
Description
stateMachineArn
Required
string | undefined

The Amazon Resource Name (ARN) of the state machine to execute.

The stateMachineArn parameter accepts one of the following inputs:

  • An unqualified state machine ARN – Refers to a state machine ARN that isn't qualified with a version or alias ARN. The following is an example of an unqualified state machine ARN.

    arn::states:::stateMachine:

    Step Functions doesn't associate state machine executions that you start with an unqualified ARN with a version. This is true even if that version uses the same revision that the execution used.

  • A state machine version ARN – Refers to a version ARN, which is a combination of state machine ARN and the version number separated by a colon (:). The following is an example of the ARN for version 10.

    arn::states:::stateMachine::10

    Step Functions doesn't associate executions that you start with a version ARN with any aliases that point to that version.

  • A state machine alias ARN – Refers to an alias ARN, which is a combination of state machine ARN and the alias name separated by a colon (:). The following is an example of the ARN for an alias named PROD.

    arn::states:::stateMachine:myStateMachine:PROD

    Step Functions associates executions that you start with an alias ARN with that alias and the state machine version used for that execution.

input
string | undefined

The string that contains the JSON input data for the execution, for example:

"input": "{"first_name" : "test"}"

If you don't include any JSON input data, you still must include the two braces, for example: "input": "{}"

Length constraints apply to the payload size, and are expressed as bytes in UTF-8 encoding.

name
string | undefined

Optional name of the execution. This name must be unique for your Amazon Web Services account, Region, and state machine for 90 days. For more information, see Limits Related to State Machine Executions  in the Step Functions Developer Guide.

If you don't provide a name for the execution, Step Functions automatically generates a universally unique identifier (UUID) as the execution name.

A name must not contain:

  • white space

  • brackets { } [ ]

  • wildcard characters ? *

  • special characters " # % ^ | ~ $ & , ; : /

  • control characters (U+0000-001F, U+007F-009F)

To enable logging with CloudWatch Logs, the name should only contain 0-9, A-Z, a-z, - and _.

traceHeader
string | undefined

Passes the X-Ray trace header. The trace header can also be passed in the request payload.

StartExecutionCommand Output

Parameter
Type
Description
$metadata
Required
ResponseMetadata
Metadata pertaining to this request.
executionArn
Required
string | undefined

The Amazon Resource Name (ARN) that identifies the execution.

startDate
Required
Date | undefined

The date the execution is started.

Throws

Name
Fault
Details
ExecutionAlreadyExists
client

The execution has the same name as another execution (but a different input).

Executions with the same name and input are considered idempotent.

ExecutionLimitExceeded
client

The maximum number of running executions has been reached. Running executions must end or be stopped before a new execution can be started.

InvalidArn
client

The provided Amazon Resource Name (ARN) is not valid.

InvalidExecutionInput
client

The provided JSON input data is not valid.

InvalidName
client

The provided name is not valid.

KmsAccessDeniedException
client

Either your KMS key policy or API caller does not have the required permissions.

KmsInvalidStateException
client

The KMS key is not in valid state, for example: Disabled or Deleted.

KmsThrottlingException
client

Received when KMS returns ThrottlingException for a KMS call that Step Functions makes on behalf of the caller.

StateMachineDeleting
client

The specified state machine is being deleted.

StateMachineDoesNotExist
client

The specified state machine does not exist.

ValidationException
client

The input does not satisfy the constraints specified by an Amazon Web Services service.

SFNServiceException
Base exception class for all service exceptions from SFN service.