AWS CloudFormation
User Guide (API Version 2010-05-15)
« PreviousNext »
View the PDF for this guide.Go to the AWS Discussion Forum for this product.Go to the Kindle Store to download this guide in Kindle format.Did this page help you?  Yes | No |  Tell us about it...

AWS::CloudFormation::WaitCondition

Using the AWS::CloudFormation::WaitCondition and AWS::CloudFormation::WaitConditionHandle resources, you can place a wait condition in a template to make AWS CloudFormation pause the creation of the stack and wait for a signal before it continues to create the stack.

Syntax

{
   "Type" : "AWS::CloudFormation::WaitCondition",
   "Properties" : {
      "Count" : String,
      "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: String

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, it 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. This section lists the available attributes and corresponding 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

Example Simple WaitCondition example with a WaitConditionHandle and GetAtt

"Resources" : {
   "myWaitHandle" : {
      "Type" : "AWS::CloudFormation::WaitConditionHandle",
      "Properties" : { }
   },
   "myWaitCondition" : {
      "Type" : "AWS::CloudFormation::WaitCondition",
      "Properties" : {
         "Handle" : { "Ref" : "myWaitHandle" },
         "Timeout" : "300"
      }
   }
},
"Outputs" : {
   "ApplicationData" : {
      "Value" : { "Fn::GetAtt" : [ "myWaitCondition", "Data" ]},
      "Description" : "The data passed back as part of signalling the WaitCondition"
   }
}        

Example WaitCondition that waits for a Windows Server instance to start

"WindowsServerWaitHandle" : {
   "Type" : "AWS::CloudFormation::WaitConditionHandle"
},
"WindowsServerWaitCondition" : {
   "Type" : "AWS::CloudFormation::WaitCondition",
   "DependsOn" : "WindowsServer",
   "Properties" : {
      "Handle" : { "Ref" : "WindowsServerWaitHandle" },
      "Timeout" : "1800"
   }
}        

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

"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" }
   }
}