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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.
Link to this section Summary
Functions
Creates an activity.
Creates a state machine.
Deletes an activity.
Deletes a state machine.
Deletes a state machine alias.
Describes an activity.
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.
Provides information about a Map Run's configuration, progress, and results.
Provides information about a state machine's definition, its IAM role Amazon Resource Name (ARN), and configuration.
Returns details about a state machine alias.
Provides information about a state machine's definition, its execution role ARN, and configuration.
Used by workers to retrieve a task (with the specified activity ARN) which has been scheduled for execution by a running state machine.
Returns the history of the specified execution as a list of events.
Lists the existing activities.
Lists all executions of a state machine or a Map Run.
Lists all Map Runs that were started by a given state machine execution.
Lists aliases for a specified state machine ARN.
Lists versions for the specified state machine Amazon Resource Name (ARN).
Lists the existing state machines.
List tags for a given resource.
Creates a version from the current revision of a state machine.
Restarts unsuccessful executions of Standard workflows that didn't complete successfully in the last 14 days.
Starts a state machine execution.
Starts a Synchronous Express state machine execution.
Stops an execution.
Add a tag to a Step Functions resource.
Accepts the definition of a single state and executes it.
Remove a tag from a Step Functions resource
Updates an in-progress Map Run's configuration to include changes to the settings that control maximum concurrency and Map Run failure.
Updates an existing state machine by modifying its definition,
roleArn, loggingConfiguration, or EncryptionConfiguration.
Updates the configuration of an existing state machine
alias
by modifying its description or routingConfiguration.
Validates the syntax of a state machine definition specified in Amazon States Language (ASL), a JSON-based, structured language.
Link to this section Functions
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.
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.
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
Related operations:
*
DescribeStateMachineAlias
*
ListStateMachineAliases
*
UpdateStateMachineAlias
*
DeleteStateMachineAlias
Deletes an activity.
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.
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
Related operations:
*
CreateStateMachineAlias
*
DescribeStateMachineAlias
*
ListStateMachineAliases
*
UpdateStateMachineAlias
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
Related operations:
*
PublishStateMachineVersion
*
ListStateMachineVersions
Describes an activity.
This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.
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.
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.
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:
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.
Returns details about a state machine alias.
related-operations
Related operations:
*
CreateStateMachineAlias
*
ListStateMachineAliases
*
UpdateStateMachineAlias
*
DeleteStateMachineAlias
describe_state_machine_for_execution(client, input, options \\ [])
View SourceProvides 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.
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.
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.
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.
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.
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.
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
Related operations:
*
CreateStateMachineAlias
*
DescribeStateMachineAlias
*
UpdateStateMachineAlias
*
DeleteStateMachineAlias
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
Related operations:
*
PublishStateMachineVersion
*
DeleteStateMachineVersion
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.
List tags for a given resource.
Tags may only contain Unicode letters, digits, white space, or these symbols: _ . : / = + - @.
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
Related operations:
*
DeleteStateMachineVersion
*
ListStateMachineVersions
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.
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.
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.
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.
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:
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.
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.
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.
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: _ . : / = + - @.
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:
* A state's input and output processing data flow
* An Amazon Web Services service integration request and response
* An HTTP Task request and response
You can call this API on only one state at a time. The states that you can test include the following:
*
All Task types except Activity
*
*
*
*
*
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.
Remove a tag from a Step Functions resource
Updates an in-progress Map Run's configuration to include changes to the settings that control maximum concurrency and Map Run failure.
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:
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.
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
Related operations:
*
CreateStateMachineAlias
*
DescribeStateMachineAlias
*
ListStateMachineAliases
*
DeleteStateMachineAlias
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.