How to set semi-random name for S3 bucket using cloud formation

Question

I want to create a cloud formation template that creates an S3 bucket with a human readable name, but which can be run many times automatically. Below is a bucket with predefined name.

What can I do to make the name contain a human readable portion in addition to a random unique id? Something like: MyBucket-abcdabcd, MyBucket-efghefgh, MyBucket-ijklijkl.

"S3Bucket" : {
  "Type" : "AWS::S3::Bucket",
  "Properties" : {
    "BucketName": "MyBucket",
    "PublicAccessBlockConfiguration" : {
      "BlockPublicAcls" : true,
      "BlockPublicPolicy" : true
    }
  }
}

Answer 1

You have two options.

First option - you can just leave your BucketName property blank. When you leave it blank, it'll yield a name of: <stackname>-<template logical name>-<random suffix>

So, if you have stack name and template logical name that make sense, it should give you a unique bucket name every time.

Second option - use the Stack ARN suffix, which is a random guid: arn:aws:cloudformation:us-west-2:123456789012:stack/teststack/51af3dc0-da77-11e4-872e-1234567db123

!Select [2, !Split [/, !Ref AWS::StackId ]]

That would yield you '51af3dc0-da77-11e4-872e-1234567db123' You can further split that again and select a portion if you want.

!Select [0, !Split[-, !Select [2, !Split [/, !Ref AWS::StackId ]]]]

Gives you 51af3dc0