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Step Functions
Step Functions is a service that lets you coordinate 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 .
Link to this section Summary
Functions
Creates an activity.
Creates a state machine.
Deletes an activity.
Deletes a state machine.
Describes an activity.
Provides all 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.
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 the existing state machines.
List tags for a given resource.
Used by activity workers and task states using the
callback
pattern to report that the task identified by the taskToken
failed.
Used by activity workers and task states using the
callback pattern to report to Step Functions that the task represented by the specified
taskToken
is still making progress.
Used by activity workers and task states using the
callback
pattern to report that the task identified by the taskToken
completed
successfully.
Starts a state machine execution.
Starts a Synchronous Express state machine execution.
Stops an execution.
Add a tag to a Step Functions resource.
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
, or
loggingConfiguration
.
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.
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
and TracingConfiguration
. 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.
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.
If the given state machine Amazon Resource Name (ARN) is a qualified state machine ARN, it will fail with ValidationException.
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
.
For EXPRESS
state machines, the deletion will happen eventually (usually less
than a minute). Running executions may emit logs after DeleteStateMachine
API
is called.
Describes an activity.
This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.
Provides all information about a state machine execution, such as the state machine associated with the execution, the execution input and output, and relevant execution metadata.
Use this API action to return the Map Run ARN if the execution was dispatched by a 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 machine executions unless
they were dispatched by a Map Run.
Provides information about a Map Run's configuration, progress, and results.
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.
If the state machine ARN is a qualified state machine ARN, the response returned
includes the Map
state's label.
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
.
This operation is eventually consistent. The results are best effort and may not reflect very recent updates and changes.
describe_state_machine_for_execution(client, input, options \\ [])
View SourceProvides information about a state machine's definition, its execution role ARN, and configuration.
If an execution was dispatched by a Map Run, the Map Run is returned in the response. Additionally, the state machine returned will be 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.
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 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: _ . : / = + - @
.
Used by activity workers and task states using the
callback
pattern to report that the task identified by the taskToken
failed.
Used by activity workers and task states using the
callback 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 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 and task states using the
callback
pattern to report that the task identified by the taskToken
completed
successfully.
Starts a state machine execution.
If the given state machine Amazon Resource Name (ARN) is a qualified state machine ARN, it will fail with ValidationException.
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
.
StartExecution
is idempotent for STANDARD
workflows. For a STANDARD
workflow, if StartExecution
is called with the same name and input as a
running execution, the call will succeed and return the same response as the
original request. If the execution is closed or if the input is different, it
will return a 400 ExecutionAlreadyExists
error. Names can be reused after 90
days.
StartExecution
is not 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.
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: _ . : / = + - @
.
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
, or
loggingConfiguration
.
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.
If the given state machine Amazon Resource Name (ARN) is a qualified state machine ARN, it will fail with ValidationException.
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
.
All StartExecution
calls within a few seconds will use the updated
definition
and roleArn
. Executions started immediately after calling
UpdateStateMachine
may use the previous state machine definition
and
roleArn
.