aws:branch – Run conditional automation steps - AWS Systems Manager

aws:branch – Run conditional automation steps

The aws:branch action allows you to create a dynamic automation that evaluates different choices in a single step and then jumps to a different step in the runbook based on the results of that evaluation.

When you specify the aws:branch action for a step, you specify Choices that the automation must evaluate. The Choices can be based on either a value that you specified in the Parameters section of the runbook, or a dynamic value generated as the output from the previous step. The automation evaluates each choice by using a Boolean expression. If the first choice is true, then the automation jumps to the step designated for that choice. If the first choice is false, the automation evaluates the next choice. The automation continues evaluating each choice until it process a true choice. The automation then jumps to the designated step for the true choice.

If none of the choices are true, the automation checks to see if the step contains a default value. A default value defines a step that the automation should jump to if none of the choices are true. If no default value is specified for the step, then the automation processes the next step in the runbook.

The aws:branch action supports complex choice evaluations by using a combination of And, Not, and Or operators. For more information about how to use aws:branch, including example runbooks and examples that use different operators, see Using conditional statements in runbooks.

Input

Specify one or more Choices in a step. The Choices can be based on either a value that you specified in the Parameters section of the runbook, or a dynamic value generated as the output from the previous step. Here is a YAML sample that evaluates a parameter.

mainSteps:
- name: chooseOS
  action: aws:branch
  inputs:
    Choices:
    - NextStep: runWindowsCommand
      Variable: "{{Name of a parameter defined in the Parameters section. For example: OS_name}}"
      StringEquals: windows
    - NextStep: runLinuxCommand
      Variable: "{{Name of a parameter defined in the Parameters section. For example: OS_name}}"
      StringEquals: linux
    Default:
      sleep3

Here is a YAML sample that evaluates output from a previous step.

mainSteps:
- name: chooseOS
  action: aws:branch
  inputs:
    Choices:
    - NextStep: runPowerShellCommand
      Variable: "{{Name of a response object. For example: GetInstance.platform}}"
      StringEquals: Windows
    - NextStep: runShellCommand
      Variable: "{{Name of a response object. For example: GetInstance.platform}}"
      StringEquals: Linux
    Default:
      sleep3
Choices

One or more expressions that the Automation should evaluate when determining the next step to process. Choices are evaluated by using a Boolean expression. Each choice must define the following options:

  • NextStep: The next step in the runbook to process if the designated choice is true.

  • Variable: Specify either the name of a parameter that is defined in the Parameters section of the runbook. Or specify an output object from a previous step in the runbook. For more information about creating variables for aws:branch, see About creating the output variable.

  • Operation: The criteria used to evaluate the choice. The aws:branch action supports the following operations:

    String operations

    • StringEquals

    • EqualsIgnoreCase

    • StartsWith

    • EndsWith

    • Contains

    Numeric operations

    • NumericEquals

    • NumericGreater

    • NumericLesser

    • NumericGreaterOrEquals

    • NumericLesser

    • NumericLesserOrEquals

    Boolean operation

    • BooleanEquals

    Important

    When you create a runbook, the system validates each operation in the runbook. If an operation isn't supported, the system returns an error when you try to create the runbook.

Default

The name of a step the automation should jump to if none of the Choices are true.

Type: String

Required: No

Note

The aws:branch action supports And, Or, and Not operators. For examples of aws:branch that use operators, see Using conditional statements in runbooks.