State machine aliases - Amazon Step Functions
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State machine aliases

An alias is a pointer for up to two versions of the same state machine. You can create multiple aliases for your state machines. Each alias has a unique Amazon Resource Name (ARN). The alias ARN is a combination of the state machine's ARN and the alias name, separated by a colon (:). The following example shows the format of a state machine alias ARN.


You can use an alias to route traffic between one of the two state machine versions. You can also create an alias that points to a single version. Aliases can only point to state machine versions. You can't use an alias to point to another alias. You can also update an alias to point to a different version of the state machine.

            Diagram of a state machine alias. This alias sends 80 percent of requests to a
                state machine to version 1, and 20 percent of requests to version 2.

Creating a state machine alias (Console)

You can create up to 100 aliases for each state machine by using the Step Functions console or by invoking the CreateStateMachineAlias API action. To request an increase to this soft limit, use the Support Center page in the Amazon Web Services Management Console. Delete unused aliases from the console or by invoking the DeleteStateMachineAlias API action.

To create a state machine alias
  1. Open the Step Functions console, and then choose an existing state machine.

  2. On the State machine detail page, choose the Aliases tab.

  3. Choose Create new alias.

  4. On the Create alias page, do the following:

    1. Enter an Alias name.

    2. (Optional) Enter a Description for the alias.

  5. To configure routing on the alias, see Alias routing configuration.

  6. Choose Create alias.

Managing aliases with Step Functions API operations

Step Functions provides the following API operations that you can use to create and manage state machine aliases or get information about the aliases:

To create an alias named PROD that points to version 1 of a state machine named myStateMachine using the Amazon Command Line Interface, use the create-state-machine-alias command.

aws stepfunctions create-state-machine-alias --name PROD --routing-configuration "[{\"stateMachineVersionArn\":\"arn:aws-cn:states:us-east-1:123456789012:stateMachine:myStateMachine:1\",\"weight\":100}]"

Alias routing configuration

You can use an alias to route execution traffic between two versions of a state machine. For example, say you want to launch a new version of your state machine. You can reduce the risks involved in deploying the new version by configuring routing on an alias. By configuring routing, you can send most of your traffic to an earlier, tested version of your state machine. The new version can then receive a smaller percentage, until you can confirm that it's safe to roll forward the new version.

To define routing configuration, make sure that you publish both state machine versions that your alias points to. When you start an execution from an alias, Step Functions randomly chooses the state machine version to run from the versions specified in the routing configuration. It bases this choice on the traffic percentage that you assign to each version in the alias routing configuration.

To configure routing configuration on an alias
  • On the Create alias page, under Routing configuration, do the following:

    1. For Version, choose the first state machine version that the alias points to.

    2. Select the Split traffic between two versions check box.


      To point to a single version, clear the Split traffic between two versions check box.

    3. For Version, choose the second version that the alias must point to.

    4. In the Traffic percentage fields, specify the percentage of traffic to route to each version. For example, enter 60 and 40 to route 60 percent of the execution traffic to the first version and 40 percent traffic to the second version.

      The combined traffic percentages must equal to 100 percent.

Running a state machine using an alias (Console)

You can start state machine executions with an alias from either the console or by invoking the StartExecution API action with the alias' ARN. Step Functions then runs the version specified by the alias. By default, if you don't specify a version or alias when you start a state machine execution, Step Functions uses the most recent revision.

To start a state machine execution using an alias
  1. Open the Step Functions console, then choose an existing state machine that you've created an alias for. For information about creating an alias, see Creating a state machine alias (Console).

  2. On the State machine detail page, choose the Aliases tab.

  3. In the Aliases section, do the following:

    1. Select the alias that you want to start the execution with.

    2. Choose Start execution.

  4. (Optional) In the Start execution dialog box, enter a name for the execution.

  5. If required, enter the execution input, and then choose Start execution.