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1. Must be sent to the controller broker
2. If there are multiple instructions for the same topic in one request the extra request will be ingnored
   • This is because the list of topics is modeled server side as a set
   • Multiple deletes results in the same end goal, so handling this error for the user should be okay
3. When requesting to delete a topic that does not exist, a an InvalidTopic error will be returned for that topic.
4. When requesting to delete a topic that is already marked for deletion, the request will wait up to the timeout until the delete is "complete" and return as usual.
   • This is to avoid errors due to concurrent delete requests. The end result is the same, the topic is deleted.
5. The principal must be authorized to the "Delete" Operation on the "Topic" resource to delete the topic. 
   • Unauthorized requests will receive a TopicAuthorizationException if they are authorized to the "Describe" Operation on the "Topic" resource
   • Otherwise they will receive an InvalidTopicException as if the topic does not exist. 
     
6. Setting a timeout > 0 will allow the request to block until the delete is "complete" on the controller node.
   • Complete means the local topic metadata cache no longer contains the topic
     • The topic metadata is updated when the controller sends out update metadata requests to the brokers
   • If a timeout error occurs, the topic could still be deleted successfully at a later time. Its up to the client to query for the state at that point.
7. Setting a timeout <= 0 will validate arguments and trigger the delete topics and return immediately. 
   • This is essentially the fully asynchronous mode we have in the Zookeeper tools today. 
   • The error code in the response will either contain an argument validation exception or a timeout exception. If you receive a timeout exception, because you asked for 0 timeout, you can assume the message was valid and the topic deletion was triggered. 
8. The request is not transactional. 
   1. If an error occurs on one topic, the others could still be deleted.
   2. Errors are reported independently.

QA:

• Why is DeleteTopicsRequest a batch request?
  • Scenarios where tools or admins want to delete many topics should be able to with fewer requests
  • Example: Removing all cluster topics
• What happens if some topics error immediately? Will it return immediately? 
  • The request will block until all topics have either been deleted, errors, or the timeout has been hit
  • There is no "short circuiting" where 1 error stops the other topics from being deleted
• Why have a timeout at all? Deletes could take a while?
  • True some deletes may take a while or never finish, however some admin tools may want extended blocking regardless. 
  • If you don't want any blocking setting a timeout of 0 works.
  • Future changes may make deletes much faster. See the Follow Up Changes section above.
• Why implement "partial blocking" instead of fully async or fully consistent?
  • See Cluster Consistent Blocking below
• Why require the request to go to the controller?
  • The controller is responsible for the cluster metadata and its propagation 
  • See Request Forwarding below

ListAcls Response (Version: 0) => [responses] error_code 
  responses => resource [acls] 
    resource => resource_type resource_name 
      resource_type => INT8
      resource_name => STRING
    acls => acl_principal acl_permission_type acl_host acl_operation 
      acl_principal => STRING
      acl_permission_type => INT8
      acl_host => STRING
      acl_operation => INT8
  error_code => INT16

Alter ACLs Request

AlterAcls Request (Version: 0) => [requests] 
  requests => resource [actions]     
    resource => resource_type resource_name 
      resource_type => INT8
      resource_name => STRING
    actions => action acl 
      action => INT8
      acl => acl_principal acl_permission_type acl_host acl_operation 
        acl_principal => STRING
        acl_permission_type => INT8
        acl_host => STRING
        acl_operation => INT8