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AWS Step Functions
AWS 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 AWS, your own servers, or any system that has access to AWS. You can access and use Step Functions using the console, the AWS SDKs, or an HTTP API. For more information about Step Functions, see the AWS 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.
Describes an execution.
Describes a state machine.
Describes the state machine associated with a specific execution.
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 the executions of a state machine that meet the filtering criteria.
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 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 AWS 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 AWS 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.
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.
Describes an execution.
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.
Describes a state machine.
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 SourceDescribes the state machine associated with a specific execution.
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.
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 the executions of a state machine that meet the filtering criteria.
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 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.
StartExecution
is idempotent. 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.
Starts a Synchronous Express state machine execution.
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 AWS 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 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.
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
.