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From Ismael Juma <ism...@juma.me.uk>
Subject Re: [DISCUSS] KIP-4 Create Topic Schema
Date Tue, 14 Jun 2016 20:09:04 GMT
Hi Grant,

Thanks for the proposal. A few comments and questions below.

On Fri, Jun 10, 2016 at 6:21 PM, Grant Henke <ghenke@cloudera.com> wrote:

> > CreateTopic Request (Version: 0) => [create_topic_requests] timeout
> >   create_topic_requests => topic partitions replication_factor
> [replica_assignment] [configs]
> >     topic => STRING
> >     partitions => INT32
>

`partition_count` or  `num_partitions` seems clearer to me.

>     replication_factor => INT32
>

I wondered if this should be `INT16`. Maybe not worth it as it won't make
much of a difference in terms of the request size though.

>    2. Multiple instructions for the same topic in one request will be
> >    silently ignored, only the last from the list will be executed.
> >       - This is because the list of topics is modeled server side as a
> >       map with TopicName as the key
>

Silently ignoring what is likely a user error makes me uncomfortable
generally. Is this really the best option?


> >    3. The principle must be authorized to the "Create" Operation on the
> >    "Cluster" resource to create topics.
> >       - Unauthorized requests will receive a
> ClusterAuthorizationException
>

Now that we are starting to use the `Create` operation, are we sure that
the right model doesn't involve specifying the resource type? It seems to
me that a `Create Topics` permission would make more sense as that would
allow someone to be given `Create Topics` permission, but not `Create ACLs`
for example. Was this discussed and discarded already?


> >    4.
> >
> >    Only one from ReplicaAssignment or (Partitions + ReplicationFactor),
> can
> >    be defined in one instruction. If both parameters are specified -
> >    ReplicaAssignment takes precedence.
>

This is similar to `2`, do we want to silently ignore data from the user or
fail-fast?


> >    - In the case ReplicaAssignment is defined number of partitions and
> >       replicas will be calculated from the supplied ReplicaAssignment.
> >       - In the case of defined (Partitions + ReplicationFactor) replica
> >       assignment will be automatically generated by the server.
> >       - One or the other must be defined. The existing broker side auto
> >       create defaults will not be used
> >       (default.replication.factor, num.partitions). The client
> implementation can
> >       have defaults for these options when generating the messages.
> >    5. Setting a timeout > 0 will allow the request to block until the
> >    topic metadata is "complete" on the controller node.
>

What happens if timeout < 0?


> >    - Why is CreateTopicRequest a batch request?
>

Should it be `CreateTopicsRequest` then?

Thanks,
Ismael

P.S. I fixed a couple of typos I spotted on the wiki page, I hope that's OK.

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