Current state: Under Discussion
Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Kafka already has user configurable policies which can be used by a cluster administrator to limit how the cluster can be modified by non-administrator users using the AdminClient API:
- TopicCreationPolicy can prevent a topic being created based on topic creation parameters (name, number of partitions & replication factor or replica assignments, topic configs)
- AlterConfigPolicy can prevent a change to topic config (or, in theory, broker config, but it's current not possible to change broker configs via the AdminClient API)
As new APIs are added to the AdminClient we need to apply policies to them, but the existing policy interfaces make it difficult to do in a consistent way.
Changing the number of partitions in a topic (KIP-195) is one kind of topic modification. Consider:
- It shouldn't be possible to create a topic, but then modify it so that it no longer conforms to the
- An administrator who wants to prevent increasing the number of partitions entirely for topics with keys, because of the effect on partitioning.
So there needs to be a policy for modifying a topic in this way. But it is confusing and error-prone if there are different policy classes for creation and modification. So there should be a single policy interface which is applied to both topic creation and modification. We could apply the
TopicCreationPolicy to modifications, but this would obscure whether a particular invocation of the policy was for a topic creation or modification (the second bullet). So we conclude we need a different policy than
Reassigning replicas is another kind of topic modification (KIP-179). By similar reasoning to example 1 it, too, should be covered by the same policy.
KIP-170 proposes a TopicDeletionPolicy
Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.
A public interface is any change to the following:
Binary log format
The network protocol and api behavior
Any class in the public packages under clientsConfiguration, especially client configuration
org/apache/kafka/clients/consumer (eventually, once stable)
Command line tools and arguments
- Anything else that will likely break existing users in some way when they upgrade
Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.
Compatibility, Deprecation, and Migration Plan
- What impact (if any) will there be on existing users?
- If we are changing behavior how will we phase out the older behavior?
- If we need special migration tools, describe them here.
- When will we remove the existing behavior?
If there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.