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AWS CloudFormation
User Guide (API Version 2010-05-15)

AWS Documentation » AWS CloudFormation » User Guide » Template Reference » AWS Resource and Property Types Reference » AWS CloudFormation Resource Types Reference » AWS::CloudFormation::WaitCondition

AWS::CloudFormation::WaitCondition

Important

For Amazon EC2 and Auto Scaling resources, we recommend that you use a CreationPolicy attribute instead of wait conditions. Add a CreationPolicy attribute to those resources, and use the cfn-signal helper script to signal when an instance creation process has completed successfully.

You can use a wait condition for situations like the following:

  • To coordinate stack resource creation with configuration actions that are external to the stack creation

  • To track the status of a configuration process

For these situations, we recommend that you associate a CreationPolicy attribute with the wait condition so that you don't have to use a wait condition handle. For more information and an example, see Creating Wait Conditions in a Template. If you use a CreationPolicy with a wait condition, do not specify any of the wait condition's properties.

Note

If you use the VPC endpoint feature, resources in the VPC that respond to wait conditions must have access to AWS CloudFormation-specific Amazon Simple Storage Service (Amazon S3) buckets. Resources must send wait condition responses to a pre-signed Amazon S3 URL. If they can't send responses to Amazon S3, AWS CloudFormation won't receive a response and the stack operation fails. For more information, see Setting Up VPC Endpoints for AWS CloudFormation.

Syntax

To declare this entity in your AWS CloudFormation template, use the following syntax:

JSON

{
   "Type" : "AWS::CloudFormation::WaitCondition",
   "Properties" : {
      "Count" : Integer,
      "Handle" : String,
      "Timeout" : String
   }
}

YAML

Type: AWS::CloudFormation::WaitCondition
Properties: 
  Count: Integer
  Handle: String
  Timeout: String

Properties

Count

The number of success signals that AWS CloudFormation must receive before it continues the stack creation process. When the wait condition receives the requisite number of success signals, AWS CloudFormation resumes the creation of the stack. If the wait condition does not receive the specified number of success signals before the Timeout period expires, AWS CloudFormation assumes that the wait condition has failed and rolls the stack back.

Required: No

Type: Integer

Update requires: Updates are not supported.

Handle

A reference to the wait condition handle used to signal this wait condition. Use the Ref intrinsic function to specify an AWS::CloudFormation::WaitConditionHandle resource.

Anytime you add a WaitCondition resource during a stack update, you must associate the wait condition with a new WaitConditionHandle resource. Do not reuse an old wait condition handle that has already been defined in the template. If you reuse a wait condition handle, the wait condition might evaluate old signals from a previous create or update stack command.

Required: Yes

Type: String

Update requires: Updates are not supported.

Timeout

The length of time (in seconds) to wait for the number of signals that the Count property specifies. Timeout is a minimum-bound property, meaning the timeout occurs no sooner than the time you specify, but can occur shortly thereafter. The maximum time that can be specified for this property is 12 hours (43200 seconds).

Required: Yes

Type: String

Update requires: Updates are not supported.

Return Values

Ref

When the logical ID of this resource is provided to the Ref intrinsic function, Ref returns the resource name.

For more information about using the Ref function, see Ref.

Fn::GetAtt

Fn::GetAtt returns a value for a specified attribute of this type. The following are the available attributes and sample return values.

Data

Returns: A JSON object that contains the UniqueId and Data values from the wait condition signal(s) for the specified wait condition. For more information about wait condition signals, see Wait Condition Signal JSON Format.

Example return value for a wait condition with 2 signals:


{ "Signal1" : "Step 1 complete." , "Signal2" : "Step 2 complete." }

For more information about using Fn::GetAtt, see Fn::GetAtt.

Examples

WaitCondition that waits for the desired number of instances in a web server group

JSON

"WebServerGroup" : {
   "Type" : "AWS::AutoScaling::AutoScalingGroup",
   "Properties" : {
      "AvailabilityZones" : { "Fn::GetAZs" : "" },
      "LaunchConfigurationName" : { "Ref" : "LaunchConfig" },
      "MinSize" : "1",
      "MaxSize" : "5",
      "DesiredCapacity" : { "Ref" : "WebServerCapacity" },
      "LoadBalancerNames" : [ { "Ref" : "ElasticLoadBalancer" } ]
   }
},

"WaitHandle" : {
   "Type" : "AWS::CloudFormation::WaitConditionHandle"
},

"WaitCondition" : {
   "Type" : "AWS::CloudFormation::WaitCondition",
   "DependsOn" : "WebServerGroup",
   "Properties" : {
      "Handle"  : { "Ref" : "WaitHandle" },
      "Timeout" : "300",
      "Count"   : { "Ref" : "WebServerCapacity" }
   }
}

YAML

WebServerGroup: 
  Type: AWS::AutoScaling::AutoScalingGroup
  Properties: 
    AvailabilityZones: 
      Fn::GetAZs: ""
    LaunchConfigurationName: 
      Ref: "LaunchConfig"
    MinSize: "1"
    MaxSize: "5"
    DesiredCapacity: 
      Ref: "WebServerCapacity"
    LoadBalancerNames: 
      - 
        Ref: "ElasticLoadBalancer"
WaitHandle: 
  Type: AWS::CloudFormation::WaitConditionHandle
WaitCondition: 
  Type: AWS::CloudFormation::WaitCondition
  DependsOn: "WebServerGroup"
  Properties: 
    Handle: 
      Ref: "WaitHandle"
    Timeout: "300"
    Count: 
      Ref: "WebServerCapacity"

See Also