AWS CloudFormation: What is causing resources creation to be cancelled and how to debug?

Question

I have no idea how to debug this cloudformation template from https://github.com/vrivellino/clojure-west-2014-demo/blob/master/config/cfn-template.json

I do not think this is datomic related, I think it's something wrong with the cf template (since it is 2 years old now).

I follow the directions and everything goes smoothly, but when I check the cloudformation it results in failing with the following in the events, but doesn't offer any helpful reasons as to why it failed. How do I get more information in CF so it will let me find out what's wrong with my template?

myapp:28:17 UTC-0700    ROLLBACK_COMPLETE   AWS::CloudFormation::Stack  myapp-staging   
myapp:28:16 UTC-0700    DELETE_COMPLETE AWS::IAM::Role  TransRole   
myapp:28:15 UTC-0700    DELETE_COMPLETE AWS::IAM::User  CfnUser 
myapp:28:13 UTC-0700    DELETE_COMPLETE AWS::IAM::Role  PeerRole    
myapp:28:12 UTC-0700    DELETE_COMPLETE AWS::ElasticLoadBalancing::LoadBalancer ElasticLoadBalancer 
myapp:28:12 UTC-0700    DELETE_COMPLETE AWS::EC2::SecurityGroup PeerSecGrp  
myapp:28:12 UTC-0700    DELETE_COMPLETE AWS::CloudWatch::Alarm  DatomicMemIndexMB   
myapp:28:12 UTC-0700    DELETE_COMPLETE AWS::CloudWatch::Alarm  DatomicAlarm    
myapp:28:12 UTC-0700    DELETE_COMPLETE AWS::EC2::SecurityGroup TransactorSecGrp    
myapp:28:12 UTC-0700    DELETE_COMPLETE AWS::CloudWatch::Alarm  DatomicSuicide  
myapp:28:12 UTC-0700    DELETE_COMPLETE AWS::CloudWatch::Alarm  DatomicStoragePutBackoff    
myapp:28:12 UTC-0700    DELETE_IN_PROGRESS  AWS::ElasticLoadBalancing::LoadBalancer ElasticLoadBalancer 
myapp:28:12 UTC-0700    DELETE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicAlarm    
myapp:28:12 UTC-0700    DELETE_IN_PROGRESS  AWS::IAM::Role  TransRole   
myapp:28:12 UTC-0700    DELETE_IN_PROGRESS  AWS::IAM::User  CfnUser 
myapp:28:12 UTC-0700    DELETE_IN_PROGRESS  AWS::EC2::SecurityGroup PeerSecGrp  
myapp:28:12 UTC-0700    DELETE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicStoragePutBackoff    
myapp:28:11 UTC-0700    DELETE_IN_PROGRESS  AWS::IAM::Role  PeerRole    
myapp:28:11 UTC-0700    DELETE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicSuicide  
myapp:28:11 UTC-0700    DELETE_IN_PROGRESS  AWS::EC2::SecurityGroup TransactorSecGrp    
myapp:28:08 UTC-0700    ROLLBACK_IN_PROGRESS    AWS::CloudFormation::Stack  myapp-staging   The following resource(s) failed to create: [TransactorSecGrp, TransRole, PeerRole, PeerSecGrp, ElasticLoadBalancer, CfnUser, DatomicMemIndexMB]. . Rollback requested by user.
myapp:28:07 UTC-0700    CREATE_FAILED   AWS::EC2::SecurityGroup PeerSecGrp  Resource creation cancelled
myapp:28:06 UTC-0700    CREATE_FAILED   AWS::EC2::SecurityGroup TransactorSecGrp    Resource creation cancelled
myapp:27:52 UTC-0700    CREATE_FAILED   AWS::ElasticLoadBalancing::LoadBalancer ElasticLoadBalancer Resource creation cancelled
myapp:27:52 UTC-0700    CREATE_FAILED   AWS::IAM::User  CfnUser Resource creation cancelled
myapp:27:52 UTC-0700    CREATE_FAILED   AWS::IAM::Role  TransRole   Resource creation cancelled
myapp:27:52 UTC-0700    CREATE_FAILED   AWS::IAM::Role  PeerRole    Resource creation cancelled
myapp:27:51 UTC-0700    CREATE_COMPLETE AWS::CloudWatch::Alarm  DatomicStoragePutBackoff    
myapp:27:51 UTC-0700    CREATE_COMPLETE AWS::CloudWatch::Alarm  DatomicAlarm    
myapp:27:51 UTC-0700    CREATE_IN_PROGRESS  AWS::EC2::SecurityGroup PeerSecGrp  
myapp:27:51 UTC-0700    CREATE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicStoragePutBackoff    Resource creation Initiated
myapp:27:51 UTC-0700    CREATE_COMPLETE AWS::CloudWatch::Alarm  DatomicSuicide  
myapp:27:51 UTC-0700    CREATE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicAlarm    Resource creation Initiated
myapp:27:51 UTC-0700    CREATE_IN_PROGRESS  AWS::IAM::User  CfnUser Resource creation Initiated
myapp:27:51 UTC-0700    CREATE_IN_PROGRESS  AWS::ElasticLoadBalancing::LoadBalancer ElasticLoadBalancer 
myapp:27:51 UTC-0700    CREATE_FAILED   AWS::CloudWatch::Alarm  DatomicMemIndexMB   A separate request to update this alarm is in progress.
myapp:27:51 UTC-0700    CREATE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicSuicide  Resource creation Initiated
Physical ID:myapp-staging-DatomicSuicide-fasfafsf3
myapp:27:50 UTC-0700    CREATE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicStoragePutBackoff    
myapp:27:50 UTC-0700    CREATE_IN_PROGRESS  AWS::IAM::User  CfnUser 
myapp:27:50 UTC-0700    CREATE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicAlarm    
myapp:27:50 UTC-0700    CREATE_IN_PROGRESS  AWS::EC2::SecurityGroup TransactorSecGrp    
myapp:27:50 UTC-0700    CREATE_IN_PROGRESS  AWS::IAM::Role  PeerRole    
myapp:27:50 UTC-0700    CREATE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicSuicide  
myapp:27:50 UTC-0700    CREATE_IN_PROGRESS  AWS::CloudWatch::Alarm  DatomicMemIndexMB   
myapp:27:50 UTC-0700    CREATE_IN_PROGRESS  AWS::IAM::Role  TransRole   
myapp:27:46 UTC-0700    CREATE_IN_PROGRESS  AWS::CloudFormation::Stack  myapp-staging   User Initiated

Answer 1

I know nothing about Datomic, but the error in the event log posted is the following:

myapp:27:51 UTC-0700    CREATE_FAILED   AWS::CloudWatch::Alarm  DatomicMemIndexMB   A separate request to update this alarm is in progress.

The other errors are Resource creation cancelled which are triggered after the initial error is raised and the automatic rollback of all updated/updating resources is initiated.

Beyond knowing that the A separate request to update this alarm is in progress error was raised on your DatomicMemIndexMB resource of type AWS::CloudWatch::Alarm, there is no more information available from CloudFormation. The implementation of the AWS::CloudWatch::Alarm resource is proprietary to AWS, so you can't determine what this error exactly means in any further detail. However, if there's something obvious such as an existing CloudWatch alarm already named DatomicMemIndexMB or if you're trying to create/update two CloudFormation stacks at the same time, that's probably the cause of this specific error.