Monitoring the progress of a stack update - Amazon CloudFormation
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Monitoring the progress of a stack update

You can monitor the progress of a stack update by viewing the stack's events. The console's Events tab displays each major step in the creation and update of the stack sorted by the time of each event with latest events on top.

Events generated during a successful stack update

The start of the stack update process is marked with an UPDATE_IN_PROGRESS event for the stack:

2011-09-30 09:35 PDT AWS::CloudFormation::Stack MyStack UPDATE_IN_PROGRESS

Next are events that mark the beginning and completion of the update of each resource that was changed in the update template. For example, updating an AWS::RDS::DBInstance resource named MyDB would result in the following entries:

2011-09-30 09:35 PDT AWS::RDS::DBInstance MyDB UPDATE_COMPLETE 2011-09-30 09:35 PDT AWS::RDS::DBInstance MyDB UPDATE_IN_PROGRESS

The UPDATE_IN_PROGRESS event is logged when Amazon CloudFormation reports that it has begun to update the resource. The UPDATE_COMPLETE event is logged when the resource is successfully created.

When Amazon CloudFormation has successfully updated the stack, you will see the following event:

2011-09-30 09:35 PDT AWS::CloudFormation::Stack MyStack UPDATE_COMPLETE

During stack update operations, if CloudFormation needs to replace an existing resource, it first creates a new resource and then deletes the old resource. However, there may be cases where CloudFormation can't delete the old resource (for example, if the user doesn't have permissions to delete a resource of a given type).

CloudFormation makes three attempts at deleting the old resource. If CloudFormation can't delete the old resource, it removes the old resource from the stack and continues updating the stack. When the stack update is complete, CloudFormation issues an UPDATE_COMPLETE stack event, but includes a StatusReason that states that one or more resources couldn't be deleted. CloudFormation also issues a DELETE_FAILED event for the specific resource, with a corresponding StatusReason providing more detail on why CloudFormation failed to delete the resource.

The old resource still exists and will continue to incur charges, but is no longer accessible through CloudFormation. To delete the old resource, access the old resource directly using the console or API for the underlying service.

This is also true for resources that you have removed from the stack template, and so will be deleted from the stack during the stack update.

Events generated when a resource update fails

If an update of a resource fails, Amazon CloudFormation reports an UPDATE_FAILED event that includes a reason for the failure. For example, if your update template specified a property change that's not supported by the resource such as reducing the size of AllocatedStorage for an AWS::RDS::DBInstance resource, you would see events like these:

2011-09-30 09:36 PDT AWS::RDS::DBInstance MyDB UPDATE_FAILED Size cannot be less than current size; requested: 5; current: 10 2011-09-30 09:35 PDT AWS::RDS::DBInstance MyDB UPDATE_IN_PROGRESS

If a resource update fails, Amazon CloudFormation rolls back any resources that it has updated during the upgrade to their configurations before the update. Here is an example of the events you would see during an update rollback:

2011-09-30 09:38 PDT AWS::CloudFormation::Stack MyStack UPDATE_ROLLBACK_COMPLETE 2011-09-30 09:38 PDT AWS::RDS::DBInstance MyDB UPDATE_COMPLETE 2011-09-30 09:37 PDT AWS::RDS::DBInstance MyDB UPDATE_IN_PROGRESS 2011-09-30 09:37 PDT AWS::CloudFormation::Stack MyStack UPDATE_ROLLBACK_IN_PROGRESS The following resource(s) failed to update: [MyDB]

To view stack events by using the console

  1. In the Amazon CloudFormation console, select the stack that you updated and then choose the Events tab to view the stacks events.

  2. To update the event list with the most recent events, choose the refresh button in the Amazon CloudFormation console.

To view stack events by using the command line