Step Functions

Step Functions coordinates the components of distributed applications and microservices using visual workflows.

You can use Step Functions to build applications from individual components, each of which performs a discrete function, or task, allowing you to scale and change applications quickly. Step Functions provides a console that helps visualize the components of your application as a series of steps. Step Functions automatically triggers and tracks each step, and retries steps when there are errors, so your application executes predictably and in the right order every time. Step Functions logs the state of each step, so you can quickly diagnose and debug any issues.

Step Functions manages operations and underlying infrastructure to ensure your application is available at any scale. You can run tasks on Amazon Web Services, your own servers, or any system that has access to Amazon Web Services. You can access and use Step Functions using the console, the Amazon Web Services SDKs, or an HTTP API. For more information about Step Functions, see the Step Functions Developer Guide  .

If you use the Step Functions API actions using Amazon Web Services SDK integrations, make sure the API actions are in camel case and parameter names are in Pascal case. For example, you could use Step Functions API action startSyncExecution and specify its parameter as StateMachineArn.

Installation

NPM
npm install @aws-sdk/client-sfn
Yarn
yarn add @aws-sdk/client-sfn
pnpm
pnpm add @aws-sdk/client-sfn

SFNClient Operations

Command
Summary
CreateActivityCommand

Creates an activity. An activity is a task that you write in any programming language and host on any machine that has access to Step Functions. Activities must poll Step Functions using the GetActivityTask API action and respond using SendTask* API actions. This function lets Step Functions know the existence of your activity and returns an identifier for use in a state machine and when polling from the activity.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

CreateActivity is an idempotent API. Subsequent requests won’t create a duplicate resource if it was already created. CreateActivity's idempotency check is based on the activity name. If a following request has different tags values, Step Functions will ignore these differences and treat it as an idempotent request of the previous. In this case, tags will not be updated, even if they are different.

CreateStateMachineAliasCommand

Creates an alias  for a state machine that points to one or two versions  of the same state machine. You can set your application to call StartExecution with an alias and update the version the alias uses without changing the client's code.

You can also map an alias to split StartExecution requests between two versions of a state machine. To do this, add a second RoutingConfig object in the routingConfiguration parameter. You must also specify the percentage of execution run requests each version should receive in both RoutingConfig objects. Step Functions randomly chooses which version runs a given execution based on the percentage you specify.

To create an alias that points to a single version, specify a single RoutingConfig object with a weight set to 100.

You can create up to 100 aliases for each state machine. You must delete unused aliases using the DeleteStateMachineAlias API action.

CreateStateMachineAlias is an idempotent API. Step Functions bases the idempotency check on the stateMachineArn, description, name, and routingConfiguration parameters. Requests that contain the same values for these parameters return a successful idempotent response without creating a duplicate resource.

Related operations:

  • DescribeStateMachineAlias

  • ListStateMachineAliases

  • UpdateStateMachineAlias

  • DeleteStateMachineAlias

CreateStateMachineCommand

Creates a state machine. A state machine consists of a collection of states that can do work (Task states), determine to which states to transition next (Choice states), stop an execution with an error (Fail states), and so on. State machines are specified using a JSON-based, structured language. For more information, see Amazon States Language  in the Step Functions User Guide.

If you set the publish parameter of this API action to true, it publishes version 1 as the first revision of the state machine.

For additional control over security, you can encrypt your data using a customer-managed key for Step Functions state machines. You can configure a symmetric KMS key and data key reuse period when creating or updating a State Machine. The execution history and state machine definition will be encrypted with the key applied to the State Machine.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

CreateStateMachine is an idempotent API. Subsequent requests won’t create a duplicate resource if it was already created. CreateStateMachine's idempotency check is based on the state machine name, definition, type, LoggingConfiguration, TracingConfiguration, and EncryptionConfiguration The check is also based on the publish and versionDescription parameters. If a following request has a different roleArn or tags, Step Functions will ignore these differences and treat it as an idempotent request of the previous. In this case, roleArn and tags will not be updated, even if they are different.

DeleteActivityCommand

Deletes an activity.

DeleteStateMachineAliasCommand

Deletes a state machine alias .

After you delete a state machine alias, you can't use it to start executions. When you delete a state machine alias, Step Functions doesn't delete the state machine versions that alias references.

Related operations:

  • CreateStateMachineAlias

  • DescribeStateMachineAlias

  • ListStateMachineAliases

  • UpdateStateMachineAlias

DeleteStateMachineCommand

Deletes a state machine. This is an asynchronous operation. It sets the state machine's status to DELETING and begins the deletion process. A state machine is deleted only when all its executions are completed. On the next state transition, the state machine's executions are terminated.

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 unqualified state machine ARN refers to a state machine named myStateMachine.

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

This API action also deletes all versions  and aliases  associated with a state machine.

For EXPRESS state machines, the deletion happens eventually (usually in less than a minute). Running executions may emit logs after DeleteStateMachine API is called.

DeleteStateMachineVersionCommand

Deletes a state machine version . After you delete a version, you can't call StartExecution using that version's ARN or use the version with a state machine alias .

Deleting a state machine version won't terminate its in-progress executions.

You can't delete a state machine version currently referenced by one or more aliases. Before you delete a version, you must either delete the aliases or update them to point to another state machine version.

Related operations:

  • PublishStateMachineVersion

  • ListStateMachineVersions

DescribeActivityCommand

Describes an activity.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

DescribeExecutionCommand

Provides information about a state machine execution, such as the state machine associated with the execution, the execution input and output, and relevant execution metadata. If you've redriven  an execution, you can use this API action to return information about the redrives of that execution. In addition, you can use this API action to return the Map Run Amazon Resource Name (ARN) if the execution was dispatched by a Map Run.

If you specify a version or alias ARN when you call the StartExecution API action, DescribeExecution returns that ARN.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

Executions of an EXPRESS state machine aren't supported by DescribeExecution unless a Map Run dispatched them.

DescribeMapRunCommand

Provides information about a Map Run's configuration, progress, and results. If you've redriven  a Map Run, this API action also returns information about the redrives of that Map Run. For more information, see Examining Map Run  in the Step Functions Developer Guide.

DescribeStateMachineAliasCommand

Returns details about a state machine alias .

Related operations:

  • CreateStateMachineAlias

  • ListStateMachineAliases

  • UpdateStateMachineAlias

  • DeleteStateMachineAlias

DescribeStateMachineCommand

Provides information about a state machine's definition, its IAM role Amazon Resource Name (ARN), and configuration.

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:

This API action returns the details for a state machine version if the stateMachineArn you specify is a state machine version ARN.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

DescribeStateMachineForExecutionCommand

Provides information about a state machine's definition, its execution role ARN, and configuration. If a Map Run dispatched the execution, this action returns the Map Run Amazon Resource Name (ARN) in the response. The state machine returned is the state machine associated with the Map Run.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

This API action is not supported by EXPRESS state machines.

GetActivityTaskCommand

Used by workers to retrieve a task (with the specified activity ARN) which has been scheduled for execution by a running state machine. This initiates a long poll, where the service holds the HTTP connection open and responds as soon as a task becomes available (i.e. an execution of a task of this type is needed.) The maximum time the service holds on to the request before responding is 60 seconds. If no task is available within 60 seconds, the poll returns a taskToken with a null string.

This API action isn't logged in CloudTrail.

Workers should set their client side socket timeout to at least 65 seconds (5 seconds higher than the maximum time the service may hold the poll request).

Polling with GetActivityTask can cause latency in some implementations. See Avoid Latency When Polling for Activity Tasks  in the Step Functions Developer Guide.

GetExecutionHistoryCommand

Returns the history of the specified execution as a list of events. By default, the results are returned in ascending order of the timeStamp of the events. Use the reverseOrder parameter to get the latest events first.

If nextToken is returned, there are more results available. The value of nextToken is a unique pagination token for each page. Make the call again using the returned token to retrieve the next page. Keep all other arguments unchanged. Each pagination token expires after 24 hours. Using an expired pagination token will return an HTTP 400 InvalidToken error.

This API action is not supported by EXPRESS state machines.

ListActivitiesCommand

Lists the existing activities.

If nextToken is returned, there are more results available. The value of nextToken is a unique pagination token for each page. Make the call again using the returned token to retrieve the next page. Keep all other arguments unchanged. Each pagination token expires after 24 hours. Using an expired pagination token will return an HTTP 400 InvalidToken error.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

ListExecutionsCommand

Lists all executions of a state machine or a Map Run. You can list all executions related to a state machine by specifying a state machine Amazon Resource Name (ARN), or those related to a Map Run by specifying a Map Run ARN. Using this API action, you can also list all redriven  executions.

You can also provide a state machine alias  ARN or version  ARN to list the executions associated with a specific alias or version.

Results are sorted by time, with the most recent execution first.

If nextToken is returned, there are more results available. The value of nextToken is a unique pagination token for each page. Make the call again using the returned token to retrieve the next page. Keep all other arguments unchanged. Each pagination token expires after 24 hours. Using an expired pagination token will return an HTTP 400 InvalidToken error.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

This API action is not supported by EXPRESS state machines.

ListMapRunsCommand

Lists all Map Runs that were started by a given state machine execution. Use this API action to obtain Map Run ARNs, and then call DescribeMapRun to obtain more information, if needed.

ListStateMachineAliasesCommand

Lists aliases  for a specified state machine ARN. Results are sorted by time, with the most recently created aliases listed first.

To list aliases that reference a state machine version , you can specify the version ARN in the stateMachineArn parameter.

If nextToken is returned, there are more results available. The value of nextToken is a unique pagination token for each page. Make the call again using the returned token to retrieve the next page. Keep all other arguments unchanged. Each pagination token expires after 24 hours. Using an expired pagination token will return an HTTP 400 InvalidToken error.

Related operations:

  • CreateStateMachineAlias

  • DescribeStateMachineAlias

  • UpdateStateMachineAlias

  • DeleteStateMachineAlias

ListStateMachineVersionsCommand

Lists versions  for the specified state machine Amazon Resource Name (ARN).

The results are sorted in descending order of the version creation time.

If nextToken is returned, there are more results available. The value of nextToken is a unique pagination token for each page. Make the call again using the returned token to retrieve the next page. Keep all other arguments unchanged. Each pagination token expires after 24 hours. Using an expired pagination token will return an HTTP 400 InvalidToken error.

Related operations:

  • PublishStateMachineVersion

  • DeleteStateMachineVersion

ListStateMachinesCommand

Lists the existing state machines.

If nextToken is returned, there are more results available. The value of nextToken is a unique pagination token for each page. Make the call again using the returned token to retrieve the next page. Keep all other arguments unchanged. Each pagination token expires after 24 hours. Using an expired pagination token will return an HTTP 400 InvalidToken error.

This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.

ListTagsForResourceCommand

List tags for a given resource.

Tags may only contain Unicode letters, digits, white space, or these symbols: _ . : / = + - .

PublishStateMachineVersionCommand

Creates a version  from the current revision of a state machine. Use versions to create immutable snapshots of your state machine. You can start executions from versions either directly or with an alias. To create an alias, use CreateStateMachineAlias.

You can publish up to 1000 versions for each state machine. You must manually delete unused versions using the DeleteStateMachineVersion API action.

PublishStateMachineVersion is an idempotent API. It doesn't create a duplicate state machine version if it already exists for the current revision. Step Functions bases PublishStateMachineVersion's idempotency check on the stateMachineArn, name, and revisionId parameters. Requests with the same parameters return a successful idempotent response. If you don't specify a revisionId, Step Functions checks for a previously published version of the state machine's current revision.

Related operations:

  • DeleteStateMachineVersion

  • ListStateMachineVersions

RedriveExecutionCommand

Restarts unsuccessful executions of Standard workflows that didn't complete successfully in the last 14 days. These include failed, aborted, or timed out executions. When you redrive  an execution, it continues the failed execution from the unsuccessful step and uses the same input. Step Functions preserves the results and execution history of the successful steps, and doesn't rerun these steps when you redrive an execution. Redriven executions use the same state machine definition and execution ARN as the original execution attempt.

For workflows that include an Inline Map  or Parallel  state, RedriveExecution API action reschedules and redrives only the iterations and branches that failed or aborted.

To redrive a workflow that includes a Distributed Map state whose Map Run failed, you must redrive the parent workflow . The parent workflow redrives all the unsuccessful states, including a failed Map Run. If a Map Run was not started in the original execution attempt, the redriven parent workflow starts the Map Run.

This API action is not supported by EXPRESS state machines.

However, you can restart the unsuccessful executions of Express child workflows in a Distributed Map by redriving its Map Run. When you redrive a Map Run, the Express child workflows are rerun using the StartExecution API action. For more information, see Redriving Map Runs .

You can redrive executions if your original execution meets the following conditions:

  • The execution status isn't SUCCEEDED.

  • Your workflow execution has not exceeded the redrivable period of 14 days. Redrivable period refers to the time during which you can redrive a given execution. This period starts from the day a state machine completes its execution.

  • The workflow execution has not exceeded the maximum open time of one year. For more information about state machine quotas, see Quotas related to state machine executions .

  • The execution event history count is less than 24,999. Redriven executions append their event history to the existing event history. Make sure your workflow execution contains less than 24,999 events to accommodate the ExecutionRedriven history event and at least one other history event.

SendTaskFailureCommand

Used by activity workers, Task states using the callback  pattern, and optionally Task states using the job run  pattern to report that the task identified by the taskToken failed.

For an execution with encryption enabled, Step Functions will encrypt the error and cause fields using the KMS key for the execution role.

A caller can mark a task as fail without using any KMS permissions in the execution role if the caller provides a null value for both error and cause fields because no data needs to be encrypted.

SendTaskHeartbeatCommand

Used by activity workers and Task states using the callback  pattern, and optionally Task states using the job run  pattern to report to Step Functions that the task represented by the specified taskToken is still making progress. This action resets the Heartbeat clock. The Heartbeat threshold is specified in the state machine's Amazon States Language definition (HeartbeatSeconds). This action does not in itself create an event in the execution history. However, if the task times out, the execution history contains an ActivityTimedOut entry for activities, or a TaskTimedOut entry for tasks using the job run  or callback  pattern.

The Timeout of a task, defined in the state machine's Amazon States Language definition, is its maximum allowed duration, regardless of the number of SendTaskHeartbeat requests received. Use HeartbeatSeconds to configure the timeout interval for heartbeats.

SendTaskSuccessCommand

Used by activity workers, Task states using the callback  pattern, and optionally Task states using the job run  pattern to report that the task identified by the taskToken completed successfully.

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.

StartSyncExecutionCommand

Starts a Synchronous Express state machine execution. StartSyncExecution is not available for STANDARD workflows.

StartSyncExecution will return a 200 OK response, even if your execution fails, because the status code in the API response doesn't reflect function errors. Error codes are reserved for errors that prevent your execution from running, such as permissions errors, limit errors, or issues with your state machine code and configuration.

This API action isn't logged in CloudTrail.

StopExecutionCommand

Stops an execution.

This API action is not supported by EXPRESS state machines.

For an execution with encryption enabled, Step Functions will encrypt the error and cause fields using the KMS key for the execution role.

A caller can stop an execution without using any KMS permissions in the execution role if the caller provides a null value for both error and cause fields because no data needs to be encrypted.

TagResourceCommand

Add a tag to a Step Functions resource.

An array of key-value pairs. For more information, see Using Cost Allocation Tags  in the Amazon Web Services Billing and Cost Management User Guide, and Controlling Access Using IAM Tags .

Tags may only contain Unicode letters, digits, white space, or these symbols: _ . : / = + - .

TestStateCommand

Accepts the definition of a single state and executes it. You can test a state without creating a state machine or updating an existing state machine. Using this API, you can test the following:

You can call this API on only one state at a time. The states that you can test include the following:

The TestState API assumes an IAM role which must contain the required IAM permissions for the resources your state is accessing. For information about the permissions a state might need, see IAM permissions to test a state .

The TestState API can run for up to five minutes. If the execution of a state exceeds this duration, it fails with the States.Timeout error.

TestState doesn't support Activity tasks , .sync or .waitForTaskToken service integration patterns , Parallel , or Map  states.

UntagResourceCommand

Remove a tag from a Step Functions resource

UpdateMapRunCommand

Updates an in-progress Map Run's configuration to include changes to the settings that control maximum concurrency and Map Run failure.

UpdateStateMachineAliasCommand

Updates the configuration of an existing state machine alias  by modifying its description or routingConfiguration.

You must specify at least one of the description or routingConfiguration parameters to update a state machine alias.

UpdateStateMachineAlias is an idempotent API. Step Functions bases the idempotency check on the stateMachineAliasArn, description, and routingConfiguration parameters. Requests with the same parameters return an idempotent response.

This operation is eventually consistent. All StartExecution requests made within a few seconds use the latest alias configuration. Executions started immediately after calling UpdateStateMachineAlias may use the previous routing configuration.

Related operations:

  • CreateStateMachineAlias

  • DescribeStateMachineAlias

  • ListStateMachineAliases

  • DeleteStateMachineAlias

UpdateStateMachineCommand

Updates an existing state machine by modifying its definition, roleArn, loggingConfiguration, or EncryptionConfiguration. Running executions will continue to use the previous definition and roleArn. You must include at least one of definition or roleArn or you will receive a MissingRequiredParameter error.

A qualified state machine ARN refers to a Distributed Map state defined within a state machine. For example, the qualified state machine ARN arn:partition:states:region:account-id:stateMachine:stateMachineName/mapStateLabel refers to a Distributed Map state with a label mapStateLabel in the state machine named stateMachineName.

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:

After you update your state machine, you can set the publish parameter to true in the same action to publish a new version . This way, you can opt-in to strict versioning of your state machine.

Step Functions assigns monotonically increasing integers for state machine versions, starting at version number 1.

All StartExecution calls within a few seconds use the updated definition and roleArn. Executions started immediately after you call UpdateStateMachine may use the previous state machine definition and roleArn.

ValidateStateMachineDefinitionCommand

Validates the syntax of a state machine definition specified in Amazon States Language  (ASL), a JSON-based, structured language.

You can validate that a state machine definition is correct without creating a state machine resource.

Suggested uses for ValidateStateMachineDefinition:

  • Integrate automated checks into your code review or Continuous Integration (CI) process to check state machine definitions before starting deployments.

  • Run validation from a Git pre-commit hook to verify the definition before committing to your source repository.

Validation will look for problems in your state machine definition and return a result and a list of diagnostic elements.

The result value will be OK when your workflow definition can be successfully created or updated. Note the result can be OK even when diagnostic warnings are present in the response. The result value will be FAIL when the workflow definition contains errors that would prevent you from creating or updating your state machine.

The list of ValidateStateMachineDefinitionDiagnostic  data elements can contain zero or more WARNING and/or ERROR elements.

The ValidateStateMachineDefinition API might add new diagnostics in the future, adjust diagnostic codes, or change the message wording. Your automated processes should only rely on the value of the result field value (OK, FAIL). Do not rely on the exact order, count, or wording of diagnostic messages.

SFNClient Configuration

Parameter
Type
Description
defaultsMode
Optional
DefaultsMode | Provider<DefaultsMode>
The @smithy/smithy-client#DefaultsMode that will be used to determine how certain default configuration options are resolved in the SDK.
disableHostPrefix
Optional
boolean
Disable dynamically changing the endpoint of the client based on the hostPrefix trait of an operation.
extensions
Optional
RuntimeExtension[]
Optional extensions
logger
Optional
Logger
Optional logger for logging debug/info/warn/error.
maxAttempts
Optional
number | Provider<number>
Value for how many times a request will be made at most in case of retry.
profile
Optional
string
Setting a client profile is similar to setting a value for the AWS_PROFILE environment variable. Setting a profile on a client in code only affects the single client instance, unlike AWS_PROFILE.When set, and only for environments where an AWS configuration file exists, fields configurable by this file will be retrieved from the specified profile within that file. Conflicting code configuration and environment variables will still have higher priority.For client credential resolution that involves checking the AWS configuration file, the client's profile (this value) will be used unless a different profile is set in the credential provider options.
region
Optional
string | Provider<string>
The AWS region to which this client will send requests
requestHandler
Optional
__HttpHandlerUserInput
The HTTP handler to use or its constructor options. Fetch in browser and Https in Nodejs.
retryMode
Optional
string | Provider<string>
Specifies which retry algorithm to use.
useDualstackEndpoint
Optional
boolean | Provider<boolean>
Enables IPv6/IPv4 dualstack endpoint.
useFipsEndpoint
Optional
boolean | Provider<boolean>
Enables FIPS compatible endpoints.
Additional config fields are described in the full configuration type: SFNClientConfig