On Mon, Mar 13, 2017, at 22:29, Gwen Shapira wrote:
> I'm torn between my desire to get this in already and the fact that parts
> of the API feel a bit alien to Kafka.
>
> I will resolve my difficulties by giving my feedback here and then going
> to
> vote +1 on the vote thread.
> Colin can choose whether to address my concerns now or use his "unstable"
> option to wait and see...
Thanks, Gwen. I really appreciate all the feedback here, and the vote.
:)
>
> My main concern is the RequestOptions objects... It was discussed earlier
> a
> bit, but I'm not sure my particular concerns were addressed. I see the
> following issues with it:
> * They double the number of methods we have
> * They are pretty similar, so it isn't clear why we need all those
> different objects
> * All our other APIs specify timeouts either in method calls directly or
> in the configuration for the entire object.
The variants without an "options" object are for the convenience of
users who want the default options. As a practical matter, I don't see
any disadvantages to having them. If we really feel strongly about it,
we can go back to the original proposal of having users pass "null" when
they want the defaults.
The options are different classes for each operation so that they can be
extended in the future with whatever operation-specific options we think
of. If they were all the same type, this would not be possible (or we
would have bad things like options that are only valid for CreateTopics
getting passed to DeleteTopics, etc.) Different types for each allow us
to have type safety here.
There is a timeout for the entire AdminClient. This timeout is used as
the default whenever no options are specified for a call. But one
request that end-users made over and over is the ability to set a
specific timeout for individual operations, that overrode the global
default. They also strongly believed that the timeout should be on the
operation as a whole, not just a single part (like the time it spent
waiting for a response after sending the RPC, etc.)
>
> We also typically don't use methods that start with "set", but this is
> minor.
Oops! Let me fix that. Good call.
>
> The configs for NewTopic are Map<String, String> - shouldn't we use the
> LogConfig object that we already have? This will take care of
> documentation
> and be similar to ProducerConfig and ConsumerConfig?
Like Ismael said, that's part of core, not clients...
>
> My concerns aside, thank you for working on this much needed API.
Thanks for taking another look.
best,
Colin
>
> Gwen
>
> On Mon, Mar 13, 2017 at 3:26 PM, Colin McCabe <cmcc...@apache.org> wrote:
>
> > Hi Radai,
> >
> > Thanks for looking at the KIP again.
> >
> > On Mon, Mar 13, 2017, at 12:33, radai wrote:
> > > looking at the KIP as it is now, looks like all *Options objects have a
> > > common timeout property. could it be extracted to a common
> > > AdminRequestOptions or something?
> >
> > Perhaps I'm missing something, but I don't think there is any reason to
> > extract the timeout property. It doesn't simplify the implementation
> > (I've already implemented the interface in a branch, so I know this for
> > sure.) It doesn't simplify the API exposed to the users, since they
> > will still want to provide the specific option type corresponding to the
> > call. Also, as we discussed previously in the thread (about NewTopic),
> > having lot of inheritance and base classes makes it difficult to change
> > classes over time. It is better to simply use composition.
> >
> > I think it would be much better to get the AdminClient interface in, and
> > start iterating on it incrementally as we discover ways it could be
> > better. This is similar to how some things in Streams were added as
> > unstable interfaces and then stabilized over time.
> >
> > best,
> > Colin
> >
> >
> > >
> > > On Thu, Mar 9, 2017 at 2:14 PM, Colin McCabe <cmcc...@apache.org> wrote:
> > >
> > > > Hi all,
> > > >
> > > > We've been discussing this for a while (about a month) and I think
> > > > people have made some great points that improved the proposal. In
> > > > particular, adding async and batching was important. I've also been
> > > > talking with some end-users who would like to make use of this API.
> > > > Once this is in, we can iterate on it before the release, and it will
> > > > also unblock a lot of other admin proposals. I think it would be good
> > > > to start the vote in a little bit, assuming there are no objections.
> > > >
> > > > best,
> > > > Colin
> > > >
> > > >
> > > > On Wed, Mar 8, 2017, at 17:09, Colin McCabe wrote:
> > > > > On Mon, Mar 6, 2017, at 11:55, Ismael Juma wrote:
> > > > > > Thanks Colin.
> > > > > >
> > > > > > I am familiar with the protocol semantics, but we need to document
> > the
> > > > > > API
> > > > > > for users who don't know the protocol. I still think it would be
> > > > valuable
> > > > > > to have some examples of how the API would be used for common use
> > > > cases.
> > > > >
> > > > > Getting the version of all nodes in the cluster:
> > > > > Map<Node, NodeApiVersions> nodesToVersions =
> > > > > adminClient.listNodes().nodes().thenApply(
> > > > > nodes -> adminClient.apiVersions(nodes)).all().get();
> > > > >
> > > > > Creating a topic:
> > > > > adminClient.createTopic(new NewTopic("myNewTopic", 3, (short)
> > > > > 3)).all().get();
> > > > >
> > > > > Validating that a topic can be created (but not creating it):
> > > > > adminClient.createTopic(new NewTopic("myNewTopic", 3, (short) 3),
> > > > > new CreateTopicOptions().setValidateOnly(true)).all().get();
> > > > >
> > > > > > For example, say someone creates a topic and then produces to it.
> > What
> > > > > > would be the recommended way to do that?
> > > > >
> > > > > Once the future returned by createTopics has successfully completed,
> > it
> > > > > should be possible to produce to the topic.
> > > > >
> > > > > There are a few warts that are definitely worth calling out. These
> > are
> > > > > things that need to be fixed at the protocol layer, so they're
> > outside
> > > > > the scope of this KIP. But you made a good point that we need to
> > > > > document this well. Here's my list (I wonder if anyone has more?):
> > > > >
> > > > > * If auto.create.topics.enable is true on the brokers,
> > > > > AdminClient#describeTopic(topicName) may create a topic named
> > topicName.
> > > > > There are two workarounds: either use AdminClient#listTopics and
> > ensure
> > > > > that the topic is present before describing, or disable
> > > > > auto.create.topics.enable.
> > > > >
> > > > > * If delete.topic.enable is false on the brokers,
> > > > > AdminClient#deleteTopic(topicName) will mark topicName for
> > deletion, but
> > > > > not actually delete it. deleteTopic will return success in this
> > case.
> > > > >
> > > > > * It may take several seconds after AdminClient#deleteTopic returns
> > > > > success for all the brokers to become aware that the topic is gone.
> > > > > During this time, AdminClient#listTopics and
> > AdminClient#describeTopic
> > > > > may continue to return information about the deleted topic.
> > > > >
> > > > > best,
> > > > > Colin
> > > > >
> > > > >
> > > > > >
> > > > > > Ismael
> > > > > >
> > > > > > On Mon, Mar 6, 2017 at 7:43 PM, Colin McCabe <cmcc...@apache.org>
> > > > wrote:
> > > > > >
> > > > > > > On Mon, Mar 6, 2017, at 05:50, Ismael Juma wrote:
> > > > > > > > Thanks Colin. It seems like you replied to me accidentally
> > instead
> > > > of the
> > > > > > > > list, so leaving your reply below for the benefit of others.
> > > > > > >
> > > > > > > Thanks, Ismael. I actually realized my mistake right after I
> > sent to
> > > > > > > you, and re-posted it to the mailing list instead of sending
> > > > directly.
> > > > > > > Sigh...
> > > > > > >
> > > > > > > >
> > > > > > > > Regarding the disadvantage of having to hunt through the
> > request
> > > > class,
> > > > > > > > don't people have to do that anyway with the Options classes?
> > > > > > >
> > > > > > > A lot of people will simply choose the default options, until
> > they
> > > > have
> > > > > > > a reason to do otherwise (for example, they want a longer or
> > shorter
> > > > > > > timeout, etc.)
> > > > > > >
> > > > > > > >
> > > > > > > > Aside from that, it would be great if the KIP included more
> > > > detailed
> > > > > > > > javadoc for each method including information about potential
> > > > exceptions.
> > > > > > >
> > > > > > > That's a good question. Because this is an asynchronous API,
> > methods
> > > > > > > never throw exceptions. Instead, if you call get() /
> > whenComplete()
> > > > /
> > > > > > > isCompletedExceptionally() / etc. on one of the CompletableFuture
> > > > > > > objects, you will get the exception. This is to allow
> > Node.js-style
> > > > > > > completion chaining. I will add this explanation to the KIP.
> > > > > > >
> > > > > > > > I'm particularly interested in what a user can expect if a
> > create
> > > > topics
> > > > > > > > succeeds versus what they can expect if a timeout exception is
> > > > thrown. It
> > > > > > > > would be good to consider partial failures as well.
> > > > > > >
> > > > > > > This is spelled out by KIP-4.
> > > > > > >
> > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-4+-+
> > > > > > > Command+line+and+centralized+administrative+operations
> > > > > > >
> > > > > > > Specifically,
> > > > > > >
> > > > > > > > If a timeout error occurs [in CreateTopic], the topic could
> > still
> > > > be
> > > > > > > > created successfully at a later time. Its up to the client to
> > query
> > > > > > > > for the state at that point.
> > > > > > >
> > > > > > > Since we're specifically not changing the server as part of this
> > KIP,
> > > > > > > those semantics will still be in force. Of course, there are
> > plenty
> > > > of
> > > > > > > other exceptions that you can get from CreateTopics that are more
> > > > > > > meaningful, such as permission-related or network-related ones.
> > But
> > > > if
> > > > > > > you get a timeout, the operation may or may not have succeeded.
> > > > > > >
> > > > > > > Could we fix the timeout problem? Sort of. We could implement
> > > > > > > something like a retry cache. The brokers would have to
> > maintain a
> > > > > > > cache of operations (and their results) which had succeeded or
> > > > failed.
> > > > > > > Then, if an RPC got interrupted after the server had performed
> > it,
> > > > but
> > > > > > > before the client had received the response message, the client
> > could
> > > > > > > simply reconnect on another TCP session and ask the broker for
> > the
> > > > > > > result of the previous operation. The broker could look up the
> > > > result
> > > > > > > in the cache and re-send it.
> > > > > > >
> > > > > > > This fix works, but it is very complex. The cache requires
> > space in
> > > > > > > memory (and to do it perfectly, you also want to persist the
> > cache to
> > > > > > > disk in case the broker restarts and the client re-appears).
> > The fix
> > > > > > > also requires the client to wait for an indefinite amount of
> > time for
> > > > > > > the server to come back. If the client ever "gives up" and just
> > > > throws
> > > > > > > a timeout exception, we are back to not knowing what happened on
> > the
> > > > > > > server.
> > > > > > >
> > > > > > > In any case, I think we should discuss RPC change in a separate
> > > > KIP...
> > > > > > > the scope is already big enough here. Also, in practice, users
> > have
> > > > > > > workarounds for cases where there are timeouts or failures to
> > > > > > > communicate.
> > > > > > >
> > > > > > > best,
> > > > > > > Colin
> > > > > > >
> > > > > > > >
> > > > > > > > Ismael
> > > > > > > >
> > > > > > > > On Fri, Mar 3, 2017 at 9:37 PM, Colin McCabe <
> > cmcc...@apache.org>
> > > > wrote:
> > > > > > > >
> > > > > > > > > On Fri, Mar 3, 2017, at 06:41, Ismael Juma wrote:
> > > > > > > > > > Hi Colin,
> > > > > > > > > >
> > > > > > > > > > I still need to do a detailed review, but I have a couple
> > of
> > > > > > > > > > comments/questions:
> > > > > > > > > >
> > > > > > > > > > 1. I am not sure about having the options/response classes
> > as
> > > > inner
> > > > > > > > > > classes
> > > > > > > > > > of the interface. It means that file containing the
> > interface
> > > > will be
> > > > > > > > > > huge
> > > > > > > > > > eventually. And the classes are not necessarily related
> > > > either. Why
> > > > > > > not
> > > > > > > > > > use
> > > > > > > > > > a separate package for them?
> > > > > > > > >
> > > > > > > > > Yeah, I think it's reasonable to make these top-level classes
> > > > and put
> > > > > > > > > them in separate files. We can put them all in
> > > > > > > > > org.apache.kafka.clients.admin.
> > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > 2. Can you elaborate on how one decides one goes in the
> > > > Options class
> > > > > > > > > > versus the first parameter?
> > > > > > > > >
> > > > > > > > > I guess I think of options as things that you don't have to
> > > > set. For
> > > > > > > > > example, when deleting a topic, you must supply the topic
> > name,
> > > > but
> > > > > > > > > supplying a non-default timeout is optional.
> > > > > > > > >
> > > > > > > > > > I wonder if it would be simpler to just have a
> > > > > > > > > > single parameter. In that case it should probably be
> > called a
> > > > > > > Request as
> > > > > > > > > > Radai suggested, but that's a separate point and we can
> > > > discuss it
> > > > > > > > > > separately.
> > > > > > > > >
> > > > > > > > > Hmm. I don't think it would be simpler for users. It would
> > > > force
> > > > > > > > > people who just want to do something simple like delete a
> > topic
> > > > or get
> > > > > > > > > the api version of a single node to go hunting through the
> > > > request
> > > > > > > > > class.
> > > > > > > > >
> > > > > > > > > best,
> > > > > > > > > Colin
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > Ismael
> > > > > > > > > >
> > > > > > > > > > On Thu, Mar 2, 2017 at 1:58 AM, Colin McCabe <
> > > > cmcc...@apache.org>
> > > > > > > wrote:
> > > > > > > > > >
> > > > > > > > > > > On Wed, Mar 1, 2017, at 15:52, radai wrote:
> > > > > > > > > > > > quick comment on the request objects:
> > > > > > > > > > > >
> > > > > > > > > > > > i see "abstract class NewTopic" and "class
> > > > > > > NewTopicWithReplication"
> > > > > > > > > and "
> > > > > > > > > > > > NewTopicWithReplicaAssignments"
> > > > > > > > > > > >
> > > > > > > > > > > > 1. since the result object is called CreateTopicResults
> > > > should
> > > > > > > these
> > > > > > > > > be
> > > > > > > > > > > > called *Request?
> > > > > > > > > > >
> > > > > > > > > > > Hi radai,
> > > > > > > > > > >
> > > > > > > > > > > Thanks for taking a look.
> > > > > > > > > > >
> > > > > > > > > > > I think using the name "request" would be very confusing
> > > > here,
> > > > > > > because
> > > > > > > > > > > we have a whole family of internal Request classes such
> > as
> > > > > > > > > > > CreateTopicsRequest, TopicMetataRequest, etc. which are
> > used
> > > > for
> > > > > > > RPCs.
> > > > > > > > > > >
> > > > > > > > > > > > 2. this seems like a suboptimal approach to me.
> > imagine we
> > > > add a
> > > > > > > > > > > > NewTopicWithSecurity, and then we would need
> > > > > > > > > > > > NewTopicWithReplicationAndSecurity? (or any composable
> > > > > > > "traits").
> > > > > > > > > > > > this wont really scale. Wouldnt it be better to have a
> > > > single
> > > > > > > (rather
> > > > > > > > > > > complicated)
> > > > > > > > > > > > CreateTopicRequest, and use a builder pattern to deal
> > with
> > > > the
> > > > > > > > > compexity
> > > > > > > > > > > > and options? like so:
> > > > > > > > > > > >
> > > > > > > > > > > > CreateTopicRequest req =
> > > > > > > > > > > > AdminRequests.newTopic("bob").replicationFactor(2).
> > > > > > > > > > > withPartitionAssignment(1,
> > > > > > > > > > > > "boker7", "broker10").withOption(...).build();
> > > > > > > > > > > >
> > > > > > > > > > > > the builder would validate any potentially conflicting
> > > > options
> > > > > > > and
> > > > > > > > > would
> > > > > > > > > > > > allow piling on the complexity in a more manageable way
> > > > (note -
> > > > > > > my
> > > > > > > > > code
> > > > > > > > > > > > above intends to demonstrate both a general replication
> > > > factor
> > > > > > > and a
> > > > > > > > > > > > specific assignment for a partiocular partition of that
> > > > topic,
> > > > > > > which
> > > > > > > > > may
> > > > > > > > > > > > be
> > > > > > > > > > > > too much freedom).
> > > > > > > > > > >
> > > > > > > > > > > We don't need to express every optional bell and whistle
> > by
> > > > > > > creating a
> > > > > > > > > > > subclass. In fact, the proposal already had
> > setConfigs() in
> > > > the
> > > > > > > base
> > > > > > > > > > > class, since it applies to every new topic creation.
> > > > > > > > > > >
> > > > > > > > > > > Thinking about it a little more, though, the subclasses
> > don't
> > > > > > > really
> > > > > > > > > add
> > > > > > > > > > > that much value, so we should probably just have NewTopic
> > > > and no
> > > > > > > > > > > subclasses. I removed the subclasses.
> > > > > > > > > > >
> > > > > > > > > > > best,
> > > > > > > > > > > Colin
> > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > On Wed, Mar 1, 2017 at 1:58 PM, Colin McCabe <
> > > > cmcc...@apache.org
> > > > > > > >
> > > > > > > > > wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > > Hi all,
> > > > > > > > > > > > >
> > > > > > > > > > > > > Thanks for commenting, everyone. Does anyone have
> > more
> > > > > > > questions
> > > > > > > > > or
> > > > > > > > > > > > > comments, or should we vote? The latest proposal is
> > up
> > > > at
> > > > > > > > > > > > > https://cwiki.apache.org/
> > confluence/display/KAFKA/KIP-
> > > > > > > > > > > 117%3A+Add+a+public+
> > > > > > > > > > > > > AdminClient+API+for+Kafka+admin+operations
> > > > > > > > > > > > >
> > > > > > > > > > > > > best,
> > > > > > > > > > > > > Colin
> > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > > > On Thu, Feb 16, 2017, at 15:00, Colin McCabe wrote:
> > > > > > > > > > > > > > On Thu, Feb 16, 2017, at 14:11, Dong Lin wrote:
> > > > > > > > > > > > > > > Hey Colin,
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Thanks for the update. I have two comments:
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > - I actually think it is simpler and good enough
> > to
> > > > have
> > > > > > > > > per-topic
> > > > > > > > > > > API
> > > > > > > > > > > > > > > instead of batch-of-topic API. This is different
> > > > from the
> > > > > > > > > argument
> > > > > > > > > > > for
> > > > > > > > > > > > > > > batch-of-partition API because, unlike operation
> > on
> > > > topic,
> > > > > > > > > people
> > > > > > > > > > > > > usually
> > > > > > > > > > > > > > > operate on multiple partitions (e.g. seek(),
> > > > purge()) at a
> > > > > > > > > time. Is
> > > > > > > > > > > > > there
> > > > > > > > > > > > > > > performance concern with per-topic API? I am
> > > > wondering if
> > > > > > > we
> > > > > > > > > > > should do
> > > > > > > > > > > > > > > per-topic API until there is use-case or
> > performance
> > > > > > > benefits
> > > > > > > > > of
> > > > > > > > > > > > > > > batch-of-topic API.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > Yes, there is a performance concern with only
> > > > supporting
> > > > > > > > > operations
> > > > > > > > > > > on
> > > > > > > > > > > > > > one topic at a time. Jay expressed this in some
> > of his
> > > > > > > earlier
> > > > > > > > > > > emails
> > > > > > > > > > > > > > and some other people did as well. We have cases
> > in
> > > > mind for
> > > > > > > > > > > management
> > > > > > > > > > > > > > software where many topics are created at once.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > - Currently we have interface "Consumer" and
> > > > "Producer".
> > > > > > > And we
> > > > > > > > > > > also
> > > > > > > > > > > > > have
> > > > > > > > > > > > > > > implementations of these two interfaces as
> > > > "KafkaConsumer"
> > > > > > > and
> > > > > > > > > > > > > > > "KafkaProducer". If we follow the same naming
> > > > pattern,
> > > > > > > should
> > > > > > > > > we
> > > > > > > > > > > have
> > > > > > > > > > > > > > > interface "AdminClient" and the implementation
> > > > > > > > > "KafkaAdminClient",
> > > > > > > > > > > > > > > instead
> > > > > > > > > > > > > > > of the other way around?
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > That's a good point. We should do that for
> > > > consistency.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > best,
> > > > > > > > > > > > > > Colin
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Dong
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > On Thu, Feb 16, 2017 at 10:19 AM, Colin McCabe <
> > > > > > > > > cmcc...@apache.org
> > > > > > > > > > > >
> > > > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Hi all,
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > So I think people have made some very good
> > points
> > > > so far.
> > > > > > > > > There
> > > > > > > > > > > > > seems
> > > > > > > > > > > > > > > > to be agreement that we need to have explicit
> > > > batch APIs
> > > > > > > for
> > > > > > > > > the
> > > > > > > > > > > > > sake of
> > > > > > > > > > > > > > > > efficiency, so I added that back.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Contexts seem a little more complex than we
> > > > thought, so I
> > > > > > > > > removed
> > > > > > > > > > > > > that
> > > > > > > > > > > > > > > > from the proposal.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > I removed the Impl class. Instead, we now
> > have a
> > > > > > > > > > > KafkaAdminClient
> > > > > > > > > > > > > > > > interface and an AdminClient implementation. I
> > > > think
> > > > > > > this
> > > > > > > > > > > matches
> > > > > > > > > > > > > our
> > > > > > > > > > > > > > > > other code better, as Jay commented.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Each call now has an "Options" object that is
> > > > passed in.
> > > > > > > > > This
> > > > > > > > > > > will
> > > > > > > > > > > > > > > > allow us to easily add new parameters to the
> > calls
> > > > > > > without
> > > > > > > > > having
> > > > > > > > > > > > > tons
> > > > > > > > > > > > > > > > of function overloads. Similarly, each call
> > now
> > > > has a
> > > > > > > > > Results
> > > > > > > > > > > > > object,
> > > > > > > > > > > > > > > > which will let us easily extend the results we
> > are
> > > > > > > returning
> > > > > > > > > if
> > > > > > > > > > > > > needed.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > Many people made the point that Java 7 Futures
> > are
> > > > not
> > > > > > > that
> > > > > > > > > > > useful,
> > > > > > > > > > > > > but
> > > > > > > > > > > > > > > > Java 8 CompletableFutures are. With
> > > > CompletableFutures,
> > > > > > > you
> > > > > > > > > can
> > > > > > > > > > > > > chain
> > > > > > > > > > > > > > > > calls, adapt them, join them-- basically all
> > the
> > > > stuff
> > > > > > > > > people are
> > > > > > > > > > > > > doing
> > > > > > > > > > > > > > > > in Node.js and Twisted Python. Java 7 Futures
> > > > don't
> > > > > > > really
> > > > > > > > > let
> > > > > > > > > > > you
> > > > > > > > > > > > > do
> > > > > > > > > > > > > > > > anything but poll for a value or block. So I
> > felt
> > > > that
> > > > > > > it
> > > > > > > > > was
> > > > > > > > > > > > > better to
> > > > > > > > > > > > > > > > just go with a CompletableFuture-based API.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > People also made the point that they would
> > like an
> > > > easy
> > > > > > > API
> > > > > > > > > for
> > > > > > > > > > > > > waiting
> > > > > > > > > > > > > > > > on complete success of a batch call. For
> > example,
> > > > an API
> > > > > > > > > that
> > > > > > > > > > > would
> > > > > > > > > > > > > > > > fail if even one topic wasn't created in
> > > > createTopics.
> > > > > > > So I
> > > > > > > > > > > came up
> > > > > > > > > > > > > > > > with Result objects that provide multiple
> > futures
> > > > that
> > > > > > > you
> > > > > > > > > can
> > > > > > > > > > > wait
> > > > > > > > > > > > > on.
> > > > > > > > > > > > > > > > You can wait on a future that fires when
> > > > everything is
> > > > > > > > > complete,
> > > > > > > > > > > or
> > > > > > > > > > > > > you
> > > > > > > > > > > > > > > > can wait on futures for individual topics being
> > > > created.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > I updated the wiki, so please take a look.
> > Note
> > > > that
> > > > > > > this
> > > > > > > > > new
> > > > > > > > > > > API
> > > > > > > > > > > > > > > > requires JDK8. It seems like JDK8 is coming
> > soon,
> > > > > > > though,
> > > > > > > > > and
> > > > > > > > > > > the
> > > > > > > > > > > > > > > > disadvantages of sticking to Java 7 are pretty
> > big
> > > > here,
> > > > > > > I
> > > > > > > > > think.
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > best,
> > > > > > > > > > > > > > > > Colin
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > On Mon, Feb 13, 2017, at 11:51, Colin McCabe
> > wrote:
> > > > > > > > > > > > > > > > > On Sun, Feb 12, 2017, at 09:21, Jay Kreps
> > wrote:
> > > > > > > > > > > > > > > > > > Hey Colin,
> > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > Thanks for the hard work on this. I know
> > going
> > > > back
> > > > > > > and
> > > > > > > > > > > forth on
> > > > > > > > > > > > > APIs
> > > > > > > > > > > > > > > > is
> > > > > > > > > > > > > > > > > > kind of frustrating but we're at the point
> > > > where
> > > > > > > these
> > > > > > > > > things
> > > > > > > > > > > > > live long
> > > > > > > > > > > > > > > > > > enough and are used by enough people that
> > it is
> > > > > > > worth the
> > > > > > > > > > > pain.
> > > > > > > > > > > > > I'm
> > > > > > > > > > > > > > > > sure
> > > > > > > > > > > > > > > > > > it'll come down in the right place
> > eventually.
> > > > A
> > > > > > > couple
> > > > > > > > > > > things
> > > > > > > > > > > > > I've
> > > > > > > > > > > > > > > > found
> > > > > > > > > > > > > > > > > > helped in the past:
> > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > 1. The burden of evidence needs to fall
> > on
> > > > the
> > > > > > > > > > > complicator.
> > > > > > > > > > > > > i.e. if
> > > > > > > > > > > > > > > > > > person X thinks the api should be async
> > > > they need
> > > > > > > to
> > > > > > > > > > > produce
> > > > > > > > > > > > > a set
> > > > > > > > > > > > > > > > of
> > > > > > > > > > > > > > > > > > common use cases that require this.
> > > > Otherwise you
> > > > > > > are
> > > > > > > > > > > > > perpetually
> > > > > > > > > > > > > > > > > > having to
> > > > > > > > > > > > > > > > > > think "we might need x". I think it is
> > good
> > > > to
> > > > > > > have a
> > > > > > > > > > > rule of
> > > > > > > > > > > > > > > > "simple
> > > > > > > > > > > > > > > > > > until
> > > > > > > > > > > > > > > > > > proven insufficient".
> > > > > > > > > > > > > > > > > > 2. Make sure we frame things for the
> > > > intended
> > > > > > > > > audience. At
> > > > > > > > > > > > > this
> > > > > > > > > > > > > > > > point
> > > > > > > > > > > > > > > > > > our apis get used by a very broad set of
> > > > Java
> > > > > > > > > engineers.
> > > > > > > > > > > This
> > > > > > > > > > > > > is a
> > > > > > > > > > > > > > > > > > very
> > > > > > > > > > > > > > > > > > different audience from our developer
> > > > mailing
> > > > > > > list.
> > > > > > > > > These
> > > > > > > > > > > > > people
> > > > > > > > > > > > > > > > code
> > > > > > > > > > > > > > > > > > for a
> > > > > > > > > > > > > > > > > > living not necessarily as a passion, and
> > > > may not
> > > > > > > > > > > understand
> > > > > > > > > > > > > details
> > > > > > > > > > > > > > > > of
> > > > > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > internals of our system or even basic
> > > > things like
> > > > > > > > > > > > > multi-threaded
> > > > > > > > > > > > > > > > > > programming. I don't think this means we
> > > > want to
> > > > > > > dumb
> > > > > > > > > > > things
> > > > > > > > > > > > > down,
> > > > > > > > > > > > > > > > but
> > > > > > > > > > > > > > > > > > rather try really hard to make things
> > truly
> > > > simple
> > > > > > > > > when
> > > > > > > > > > > > > possible.
> > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > Okay here were a couple of comments:
> > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > 1. Conceptually what is a TopicContext?
> > I
> > > > think it
> > > > > > > > > means
> > > > > > > > > > > > > something
> > > > > > > > > > > > > > > > > > like
> > > > > > > > > > > > > > > > > > TopicAdmin? It is not literally context
> > > > about
> > > > > > > Topics
> > > > > > > > > > > right?
> > > > > > > > > > > > > What is
> > > > > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > relationship of Contexts to clients? Is
> > > > there a
> > > > > > > > > > > threadsafety
> > > > > > > > > > > > > > > > > > difference?
> > > > > > > > > > > > > > > > > > Would be nice to not have to think about
> > > > this,
> > > > > > > this is
> > > > > > > > > > > what I
> > > > > > > > > > > > > mean
> > > > > > > > > > > > > > > > by
> > > > > > > > > > > > > > > > > > "conceptual weight". We introduce a new
> > > > concept
> > > > > > > that
> > > > > > > > > is a
> > > > > > > > > > > bit
> > > > > > > > > > > > > > > > nebulous
> > > > > > > > > > > > > > > > > > that
> > > > > > > > > > > > > > > > > > I have to figure out to use what could
> > be a
> > > > simple
> > > > > > > > > api.
> > > > > > > > > > > I'm
> > > > > > > > > > > > > sure
> > > > > > > > > > > > > > > > > > you've
> > > > > > > > > > > > > > > > > > been through this experience before
> > where
> > > > you have
> > > > > > > > > these
> > > > > > > > > > > > > various
> > > > > > > > > > > > > > > > > > objects
> > > > > > > > > > > > > > > > > > and you're trying to figure out what
> > they
> > > > > > > represent
> > > > > > > > > (the
> > > > > > > > > > > > > connection
> > > > > > > > > > > > > > > > to
> > > > > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > server? the information to create a
> > > > connection? a
> > > > > > > > > request
> > > > > > > > > > > > > session?).
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > The intention was to provide some grouping of
> > > > methods,
> > > > > > > and
> > > > > > > > > > > also a
> > > > > > > > > > > > > place
> > > > > > > > > > > > > > > > > to put request parameters which were often
> > set to
> > > > > > > defaults
> > > > > > > > > > > rather
> > > > > > > > > > > > > than
> > > > > > > > > > > > > > > > > being explicitly set. If it seems complex,
> > we
> > > > can
> > > > > > > > > certainly
> > > > > > > > > > > get
> > > > > > > > > > > > > rid of
> > > > > > > > > > > > > > > > > it.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > 2. We've tried to avoid the Impl naming
> > > > > > > convention. In
> > > > > > > > > > > > > general the
> > > > > > > > > > > > > > > > > > rule
> > > > > > > > > > > > > > > > > > has been if there is only going to be
> > one
> > > > > > > > > implementation
> > > > > > > > > > > you
> > > > > > > > > > > > > don't
> > > > > > > > > > > > > > > > > > need an
> > > > > > > > > > > > > > > > > > interface. If there will be multiple,
> > > > distinguish
> > > > > > > it
> > > > > > > > > from
> > > > > > > > > > > the
> > > > > > > > > > > > > > > > others.
> > > > > > > > > > > > > > > > > > The
> > > > > > > > > > > > > > > > > > other clients follow this pattern:
> > Producer,
> > > > > > > > > > > KafkaProducer,
> > > > > > > > > > > > > > > > > > MockProducer;
> > > > > > > > > > > > > > > > > > Consumer, KafkaConsumer, MockConsumer.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > Good point. Let's change the interface to
> > > > > > > > > KafkaAdminClient,
> > > > > > > > > > > and
> > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > implementation to AdminClient.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > 3. We generally don't use setters or
> > > > getters as a
> > > > > > > > > naming
> > > > > > > > > > > > > > > > convention. I
> > > > > > > > > > > > > > > > > > personally think mutating the setting in
> > > > place
> > > > > > > seems
> > > > > > > > > kind
> > > > > > > > > > > of
> > > > > > > > > > > > > like
> > > > > > > > > > > > > > > > late
> > > > > > > > > > > > > > > > > > 90s
> > > > > > > > > > > > > > > > > > Java style. I think it likely has
> > > > thread-safety
> > > > > > > > > issues.
> > > > > > > > > > > i.e.
> > > > > > > > > > > > > even if
> > > > > > > > > > > > > > > > > > it is
> > > > > > > > > > > > > > > > > > volatile you may not get the value you
> > just
> > > > set if
> > > > > > > > > there
> > > > > > > > > > > is
> > > > > > > > > > > > > another
> > > > > > > > > > > > > > > > > > thread... I actually really liked what
> > you
> > > > > > > described
> > > > > > > > > as
> > > > > > > > > > > your
> > > > > > > > > > > > > > > > original
> > > > > > > > > > > > > > > > > > idea
> > > > > > > > > > > > > > > > > > of having a single parameter object like
> > > > > > > > > > > CreateTopicRequest
> > > > > > > > > > > > > that
> > > > > > > > > > > > > > > > holds
> > > > > > > > > > > > > > > > > > all
> > > > > > > > > > > > > > > > > > these parameters and defaults. This
> > lets you
> > > > > > > evolve
> > > > > > > > > the
> > > > > > > > > > > api
> > > > > > > > > > > > > with all
> > > > > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > various combinations of arguments
> > without
> > > > > > > overloading
> > > > > > > > > > > > > insanity.
> > > > > > > > > > > > > > > > After
> > > > > > > > > > > > > > > > > > doing
> > > > > > > > > > > > > > > > > > literally tens of thousands of remote
> > APIs
> > > > at
> > > > > > > > > LinkedIn we
> > > > > > > > > > > > > eventually
> > > > > > > > > > > > > > > > > > converged on a rule, which is ultimately
> > > > every
> > > > > > > remote
> > > > > > > > > api
> > > > > > > > > > > > > needs a
> > > > > > > > > > > > > > > > > > single
> > > > > > > > > > > > > > > > > > argument object you can add to over time
> > > > and it
> > > > > > > must
> > > > > > > > > be
> > > > > > > > > > > > > batched.
> > > > > > > > > > > > > > > > Which
> > > > > > > > > > > > > > > > > > brings me to my next point...
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > Just to clarify, volatiles were never a part
> > of
> > > > the
> > > > > > > > > proposal.
> > > > > > > > > > > I
> > > > > > > > > > > > > think
> > > > > > > > > > > > > > > > > that context objects or request objects
> > should
> > > > be used
> > > > > > > by a
> > > > > > > > > > > single
> > > > > > > > > > > > > > > > > thread at a time.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > I'm not opposed to request objects, but I
> > think
> > > > they
> > > > > > > raise
> > > > > > > > > all
> > > > > > > > > > > the
> > > > > > > > > > > > > same
> > > > > > > > > > > > > > > > > questions as context objects. Basically, the
> > > > > > > thread-safety
> > > > > > > > > > > issues
> > > > > > > > > > > > > need
> > > > > > > > > > > > > > > > > to be spelled out and understood by the user,
> > > > and the
> > > > > > > user
> > > > > > > > > > > needs
> > > > > > > > > > > > > more
> > > > > > > > > > > > > > > > > lines of code to make a request. And there
> > will
> > > > be
> > > > > > > people
> > > > > > > > > > > trying
> > > > > > > > > > > > > to do
> > > > > > > > > > > > > > > > > things like re-use request objects when they
> > > > should
> > > > > > > not,
> > > > > > > > > and so
> > > > > > > > > > > > > forth.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > 4. I agree batch apis are annoying but I
> > > > suspect
> > > > > > > we'll
> > > > > > > > > > > end up
> > > > > > > > > > > > > adding
> > > > > > > > > > > > > > > > > > one. Doing 1000 requests for 1000
> > > > operations if
> > > > > > > > > creating
> > > > > > > > > > > or
> > > > > > > > > > > > > deleting
> > > > > > > > > > > > > > > > > > will
> > > > > > > > > > > > > > > > > > be bad, right? This won't be the common
> > > > case, but
> > > > > > > when
> > > > > > > > > > > you do
> > > > > > > > > > > > > it it
> > > > > > > > > > > > > > > > > > will be
> > > > > > > > > > > > > > > > > > a deal-breaker problem. I don't think we
> > > > should
> > > > > > > try
> > > > > > > > > to fix
> > > > > > > > > > > > > this one
> > > > > > > > > > > > > > > > > > behind
> > > > > > > > > > > > > > > > > > the scenes.
> > > > > > > > > > > > > > > > > > 5. Are we going to do CompletableFuture
> > > > (which
> > > > > > > > > requires
> > > > > > > > > > > java
> > > > > > > > > > > > > 8) or
> > > > > > > > > > > > > > > > > > normal Future? Normal Future is utterly
> > > > useless
> > > > > > > for
> > > > > > > > > most
> > > > > > > > > > > > > things
> > > > > > > > > > > > > > > > other
> > > > > > > > > > > > > > > > > > than
> > > > > > > > > > > > > > > > > > just calling wait. If we can evolve in
> > > > place from
> > > > > > > > > Future
> > > > > > > > > > > to
> > > > > > > > > > > > > > > > > > CompletableFuture that is fantastic (we
> > > > could do
> > > > > > > it
> > > > > > > > > for
> > > > > > > > > > > the
> > > > > > > > > > > > > producer
> > > > > > > > > > > > > > > > > > too!).
> > > > > > > > > > > > > > > > > > My belief was that this was binary
> > > > incompatible
> > > > > > > but I
> > > > > > > > > > > > > actually don't
> > > > > > > > > > > > > > > > > > know
> > > > > > > > > > > > > > > > > > (obviously it's source compatible).
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > In my testing, replacing a return type with a
> > > > subclass
> > > > > > > of
> > > > > > > > > that
> > > > > > > > > > > > > return
> > > > > > > > > > > > > > > > > type did not break binary compatibility. I
> > > > haven't
> > > > > > > been
> > > > > > > > > able
> > > > > > > > > > > to
> > > > > > > > > > > > > find
> > > > > > > > > > > > > > > > > chapter and verse on this from the Java
> > > > implementers,
> > > > > > > > > though.
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > best,
> > > > > > > > > > > > > > > > > Colin
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > -Jay
> > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > On Wed, Feb 8, 2017 at 5:00 PM, Colin
> > McCabe <
> > > > > > > > > > > cmcc...@apache.org
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > Hi all,
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > I made some major revisions to the
> > proposal
> > > > on the
> > > > > > > > > wiki, so
> > > > > > > > > > > > > please
> > > > > > > > > > > > > > > > check
> > > > > > > > > > > > > > > > > > > it out.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > The new API is based on Ismael's
> > suggestion
> > > > of
> > > > > > > grouping
> > > > > > > > > > > > > related APIs.
> > > > > > > > > > > > > > > > > > > There is only one layer of grouping. I
> > > > think that
> > > > > > > it's
> > > > > > > > > > > > > actually
> > > > > > > > > > > > > > > > pretty
> > > > > > > > > > > > > > > > > > > intuitive. It's also based on the idea
> > of
> > > > using
> > > > > > > > > Futures,
> > > > > > > > > > > which
> > > > > > > > > > > > > > > > several
> > > > > > > > > > > > > > > > > > > people commented that they'd like to see.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > Here's a simple example:
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > AdminClient client = new
> > > > > > > AdminClientImpl(myConfig);
> > > > > > > > > > > > > > > > > > > > try {
> > > > > > > > > > > > > > > > > > > > client.topics().create("foo", 3,
> > > > (short) 2,
> > > > > > > > > > > false).get();
> > > > > > > > > > > > > > > > > > > > Collection<String> topicNames =
> > > > > > > > > > > > > client.topics().list(false).
> > > > > > > > > > > > > > > > get();
> > > > > > > > > > > > > > > > > > > > log.info("Found topics: {}",
> > > > > > > > > > > Utils.mkString(topicNames,
> > > > > > > > > > > > > ", "));
> > > > > > > > > > > > > > > > > > > > Collection<Node> nodes =
> > > > > > > > > client.nodes().list().get();
> > > > > > > > > > > > > > > > > > > > log.info("Found cluster nodes: {}",
> > > > > > > > > > > > > Utils.mkString(nodes, ",
> > > > > > > > > > > > > > > > "));
> > > > > > > > > > > > > > > > > > > > } finally {
> > > > > > > > > > > > > > > > > > > > client.close();
> > > > > > > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > The good thing is, there is no Try, no
> > 'get'
> > > > > > > prefixes,
> > > > > > > > > no
> > > > > > > > > > > > > messing
> > > > > > > > > > > > > > > > with
> > > > > > > > > > > > > > > > > > > batch APIs. If there is an error, then
> > > > > > > Future#get()
> > > > > > > > > > > throws an
> > > > > > > > > > > > > > > > > > > ExecutionException which wraps the
> > relevant
> > > > > > > exception
> > > > > > > > > in
> > > > > > > > > > > the
> > > > > > > > > > > > > standard
> > > > > > > > > > > > > > > > > > > Java way.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > Here's a slightly less simple example:
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > AdminClient client = new
> > > > > > > AdminClientImpl(myConfig);
> > > > > > > > > > > > > > > > > > > > try {
> > > > > > > > > > > > > > > > > > > > List<Future<Void>> futures = new
> > > > > > > LinkedList<>();
> > > > > > > > > > > > > > > > > > > > for (String topicName:
> > myNewTopicNames) {
> > > > > > > > > > > > > > > > > > > > creations.add(client.topics().
> > > > > > > > > > > > > > > > > > > > setClientTimeout(30000).setCr
> > > > > > > eationConfig(
> > > > > > > > > > > > > myTopicConfig).
> > > > > > > > > > > > > > > > > > > > create(topicName, 3, (short)
> > 2,
> > > > > > > false));
> > > > > > > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > > > > > > > Futures.waitForAll(futures);
> > > > > > > > > > > > > > > > > > > > } finally {
> > > > > > > > > > > > > > > > > > > > client.close();
> > > > > > > > > > > > > > > > > > > > }
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > I went with Futures because I feel like
> > > > ought to
> > > > > > > have
> > > > > > > > > some
> > > > > > > > > > > > > option for
> > > > > > > > > > > > > > > > > > > doing async. It's a style of programming
> > > > that has
> > > > > > > > > become a
> > > > > > > > > > > > > lot more
> > > > > > > > > > > > > > > > > > > popular with the rise of Node.js, Twisted
> > > > python,
> > > > > > > etc.
> > > > > > > > > etc.
> > > > > > > > > > > > > Also, as
> > > > > > > > > > > > > > > > > > > Ismael commented, Java 8
> > CompletableFuture is
> > > > > > > going to
> > > > > > > > > make
> > > > > > > > > > > > > Java's
> > > > > > > > > > > > > > > > > > > support for fluent async programming a
> > lot
> > > > > > > stronger by
> > > > > > > > > > > > > allowing call
> > > > > > > > > > > > > > > > > > > chaining and much more.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > If we are going to support async, the
> > > > simplest
> > > > > > > thing is
> > > > > > > > > > > just
> > > > > > > > > > > > > to make
> > > > > > > > > > > > > > > > > > > everything return a future and let people
> > > > call
> > > > > > > get() if
> > > > > > > > > > > they
> > > > > > > > > > > > > want to
> > > > > > > > > > > > > > > > run
> > > > > > > > > > > > > > > > > > > synchronously. Having a mix of async and
> > > > sync
> > > > > > > APIs is
> > > > > > > > > just
> > > > > > > > > > > > > going to
> > > > > > > > > > > > > > > > be
> > > > > > > > > > > > > > > > > > > confusing and redundant.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > I think we should try to avoid creating
> > > > single
> > > > > > > > > functions
> > > > > > > > > > > that
> > > > > > > > > > > > > start
> > > > > > > > > > > > > > > > > > > multiple requests if we can. It makes
> > > > things much
> > > > > > > > > > > uglier. It
> > > > > > > > > > > > > means
> > > > > > > > > > > > > > > > > > > that you have to have some kind of
> > request
> > > > class
> > > > > > > that
> > > > > > > > > > > wraps up
> > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > > request the user is trying to create, so
> > > > that you
> > > > > > > can
> > > > > > > > > > > handle an
> > > > > > > > > > > > > > > > array of
> > > > > > > > > > > > > > > > > > > those requests. The return value has to
> > be
> > > > > > > something
> > > > > > > > > like
> > > > > > > > > > > > > Map<Node,
> > > > > > > > > > > > > > > > > > > Try<Value>> to represent which nodes
> > failed
> > > > and
> > > > > > > > > succeeded.
> > > > > > > > > > > > > This is
> > > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > > kind of stuff that, in my opinion, makes
> > > > people
> > > > > > > scratch
> > > > > > > > > > > their
> > > > > > > > > > > > > heads.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > If we need to, we can still get some of
> > the
> > > > > > > efficiency
> > > > > > > > > > > > > benefits of
> > > > > > > > > > > > > > > > batch
> > > > > > > > > > > > > > > > > > > APIs by waiting for a millisecond or two
> > > > before
> > > > > > > sending
> > > > > > > > > > > out a
> > > > > > > > > > > > > topic
> > > > > > > > > > > > > > > > > > > create() request to see if other create()
> > > > requests
> > > > > > > > > > > arrive. If
> > > > > > > > > > > > > so, we
> > > > > > > > > > > > > > > > > > > can coalesce them. It might be better to
> > > > figure
> > > > > > > out if
> > > > > > > > > > > this
> > > > > > > > > > > > > is an
> > > > > > > > > > > > > > > > > > > actual performance issue before
> > implementing
> > > > it,
> > > > > > > > > though.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > I think it would be good to get
> > something out
> > > > > > > there,
> > > > > > > > > > > annotate
> > > > > > > > > > > > > it as
> > > > > > > > > > > > > > > > > > > @Unstable, and get feedback from people
> > > > building
> > > > > > > > > against
> > > > > > > > > > > trunk
> > > > > > > > > > > > > and
> > > > > > > > > > > > > > > > using
> > > > > > > > > > > > > > > > > > > it. We have removed or changed @Unstable
> > > > APIs in
> > > > > > > > > streams
> > > > > > > > > > > > > before, so
> > > > > > > > > > > > > > > > I
> > > > > > > > > > > > > > > > > > > don't think we should worry that it will
> > get
> > > > set in
> > > > > > > > > stone
> > > > > > > > > > > > > > > > prematurely.
> > > > > > > > > > > > > > > > > > > The AdminClient API should get much less
> > > > developer
> > > > > > > use
> > > > > > > > > than
> > > > > > > > > > > > > anything
> > > > > > > > > > > > > > > > in
> > > > > > > > > > > > > > > > > > > streams, so changing an unstable API
> > should
> > > > be much
> > > > > > > > > easier.
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > best,
> > > > > > > > > > > > > > > > > > > Colin
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > On Wed, Feb 8, 2017, at 07:49, Ismael
> > Juma
> > > > wrote:
> > > > > > > > > > > > > > > > > > > > Thanks for elaborating Jay. I totally
> > > > agree that
> > > > > > > we
> > > > > > > > > have
> > > > > > > > > > > to
> > > > > > > > > > > > > be very
> > > > > > > > > > > > > > > > > > > > careful
> > > > > > > > > > > > > > > > > > > > in how we use our complexity budget.
> > > > Easier said
> > > > > > > than
> > > > > > > > > > > done
> > > > > > > > > > > > > when
> > > > > > > > > > > > > > > > people
> > > > > > > > > > > > > > > > > > > > don't agree on what is complex and
> > what is
> > > > > > > simple.
> > > > > > > > > :) For
> > > > > > > > > > > > > example,
> > > > > > > > > > > > > > > > I
> > > > > > > > > > > > > > > > > > > > think
> > > > > > > > > > > > > > > > > > > > batch APIs are a significant source of
> > > > > > > complexity as
> > > > > > > > > you
> > > > > > > > > > > > > have to
> > > > > > > > > > > > > > > > do a
> > > > > > > > > > > > > > > > > > > > bunch
> > > > > > > > > > > > > > > > > > > > of ceremony to group things before
> > sending
> > > > the
> > > > > > > > > request
> > > > > > > > > > > and
> > > > > > > > > > > > > error
> > > > > > > > > > > > > > > > handling
> > > > > > > > > > > > > > > > > > > > becomes more complex due to partial
> > > > failures
> > > > > > > (things
> > > > > > > > > like
> > > > > > > > > > > > > `Try` or
> > > > > > > > > > > > > > > > other
> > > > > > > > > > > > > > > > > > > > mechanisms that serve a similar role
> > are
> > > > then
> > > > > > > > > needed).
> > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > Maybe a way forward is to write API
> > usage
> > > > > > > examples to
> > > > > > > > > > > help
> > > > > > > > > > > > > > > > validate that
> > > > > > > > > > > > > > > > > > > > the suggested API is indeed easy to
> > use.
> > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > Ismael
> > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > On Wed, Feb 8, 2017 at 4:40 AM, Jay
> > Kreps <
> > > > > > > > > > > j...@confluent.io>
> > > > > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > Totally agree on CompletableFuture.
> > Also
> > > > agree
> > > > > > > with
> > > > > > > > > > > some
> > > > > > > > > > > > > of the
> > > > > > > > > > > > > > > > rough
> > > > > > > > > > > > > > > > > > > edges
> > > > > > > > > > > > > > > > > > > > > on the Consumer.
> > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > I don't have much of a leg to stand
> > on
> > > > with the
> > > > > > > > > > > splitting
> > > > > > > > > > > > > vs not
> > > > > > > > > > > > > > > > > > > splitting
> > > > > > > > > > > > > > > > > > > > > thing, really hard to argue one or
> > the
> > > > other is
> > > > > > > > > > > better. I
> > > > > > > > > > > > > guess
> > > > > > > > > > > > > > > > the one
> > > > > > > > > > > > > > > > > > > > > observation in watching us try to
> > make
> > > > good
> > > > > > > public
> > > > > > > > > apis
> > > > > > > > > > > > > over the
> > > > > > > > > > > > > > > > years
> > > > > > > > > > > > > > > > > > > is I
> > > > > > > > > > > > > > > > > > > > > am kind of in favor of a particular
> > kind
> > > > of
> > > > > > > > > simple. In
> > > > > > > > > > > > > > > > particular I
> > > > > > > > > > > > > > > > > > > think
> > > > > > > > > > > > > > > > > > > > > since the bar is sooo high in support
> > > > and docs
> > > > > > > and
> > > > > > > > > the
> > > > > > > > > > > > > community
> > > > > > > > > > > > > > > > of
> > > > > > > > > > > > > > > > > > > users
> > > > > > > > > > > > > > > > > > > > > so broad in the range of their
> > > > capabilities, it
> > > > > > > > > makes
> > > > > > > > > > > it so
> > > > > > > > > > > > > > > > there is a
> > > > > > > > > > > > > > > > > > > lot
> > > > > > > > > > > > > > > > > > > > > of value in dead simple interfaces
> > that
> > > > don't
> > > > > > > have
> > > > > > > > > a
> > > > > > > > > > > lot of
> > > > > > > > > > > > > > > > conceptual
> > > > > > > > > > > > > > > > > > > > > weight, don't introduce a lot of new
> > > > classes or
> > > > > > > > > > > concepts or
> > > > > > > > > > > > > > > > general
> > > > > > > > > > > > > > > > > > > > > patterns that must be understood to
> > use
> > > > them
> > > > > > > > > > > correctly. So
> > > > > > > > > > > > > > > > things like
> > > > > > > > > > > > > > > > > > > > > nesting, or the Try class, or async
> > > > apis, or
> > > > > > > even
> > > > > > > > > just
> > > > > > > > > > > a
> > > > > > > > > > > > > complex
> > > > > > > > > > > > > > > > set of
> > > > > > > > > > > > > > > > > > > > > classes representing arguments or
> > return
> > > > values
> > > > > > > > > kind of
> > > > > > > > > > > > > all stack
> > > > > > > > > > > > > > > > > > > > > conceptual burdens on the user to
> > figure
> > > > out
> > > > > > > > > correct
> > > > > > > > > > > > > usage. So
> > > > > > > > > > > > > > > > like,
> > > > > > > > > > > > > > > > > > > for
> > > > > > > > > > > > > > > > > > > > > example, the Try class is very
> > elegant
> > > > and
> > > > > > > > > represents a
> > > > > > > > > > > > > whole
> > > > > > > > > > > > > > > > > > > generalized
> > > > > > > > > > > > > > > > > > > > > class of possibly completed actions,
> > but
> > > > the
> > > > > > > flip
> > > > > > > > > side
> > > > > > > > > > > is
> > > > > > > > > > > > > maybe
> > > > > > > > > > > > > > > > I'm
> > > > > > > > > > > > > > > > > > > just a
> > > > > > > > > > > > > > > > > > > > > working guy who needs to list his
> > kafka
> > > > topics
> > > > > > > but
> > > > > > > > > > > doesn't
> > > > > > > > > > > > > know
> > > > > > > > > > > > > > > > Rust,
> > > > > > > > > > > > > > > > > > > take
> > > > > > > > > > > > > > > > > > > > > pity on me! :-)
> > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > Nit picking aside, super excited to
> > see
> > > > us
> > > > > > > > > progress on
> > > > > > > > > > > > > this.
> > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > -Jay
> > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > On Tue, Feb 7, 2017 at 3:46 PM Ismael
> > > > Juma <
> > > > > > > > > > > > > ism...@juma.me.uk>
> > > > > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > Hi Jay,
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > Thanks for the feedback. Comments
> > > > inline.
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > On Tue, Feb 7, 2017 at 8:18 PM, Jay
> > > > Kreps <
> > > > > > > > > > > > > j...@confluent.io>
> > > > > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > > - I think it would be good to
> > not
> > > > use
> > > > > > > "get"
> > > > > > > > > as
> > > > > > > > > > > the
> > > > > > > > > > > > > prefix
> > > > > > > > > > > > > > > > for
> > > > > > > > > > > > > > > > > > > things
> > > > > > > > > > > > > > > > > > > > > > > making remote calls. We've
> > tried
> > > > to
> > > > > > > avoid
> > > > > > > > > the
> > > > > > > > > > > java
> > > > > > > > > > > > > getter
> > > > > > > > > > > > > > > > > > > convention
> > > > > > > > > > > > > > > > > > > > > > > entirely (see code style
> > guide),
> > > > but for
> > > > > > > > > remote
> > > > > > > > > > > > > calls in
> > > > > > > > > > > > > > > > > > > particular
> > > > > > > > > > > > > > > > > > > > > it
> > > > > > > > > > > > > > > > > > > > > > > kind
> > > > > > > > > > > > > > > > > > > > > > > of blurs the line between
> > field
> > > > access
> > > > > > > and
> > > > > > > > > > > remote
> > > > > > > > > > > > > RPC in
> > > > > > > > > > > > > > > > a way
> > > > > > > > > > > > > > > > > > > that
> > > > > > > > > > > > > > > > > > > > > > > leads
> > > > > > > > > > > > > > > > > > > > > > > people to trouble. What about,
> > > > e.g.,
> > > > > > > > > > > > > fetchAllGroups() vs
> > > > > > > > > > > > > > > > > > > > > > getAllGroups().
> > > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > Agreed that we should avoid the
> > `get`
> > > > prefix
> > > > > > > for
> > > > > > > > > > > remote
> > > > > > > > > > > > > calls.
> > > > > > > > > > > > > > > > There
> > > > > > > > > > > > > > > > > > > are
> > > > > > > > > > > > > > > > > > > > > a
> > > > > > > > > > > > > > > > > > > > > > few possible prefixes for the read
> > > > > > > operations:
> > > > > > > > > list,
> > > > > > > > > > > > > fetch,
> > > > > > > > > > > > > > > > describe.
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > > - I think futures and
> > callbacks
> > > > are a
> > > > > > > bit
> > > > > > > > > of a
> > > > > > > > > > > pain
> > > > > > > > > > > > > to
> > > > > > > > > > > > > > > > use. I'd
> > > > > > > > > > > > > > > > > > > > > second
> > > > > > > > > > > > > > > > > > > > > > > Becket's comment: let's ensure
> > > > there a
> > > > > > > > > common
> > > > > > > > > > > use
> > > > > > > > > > > > > case
> > > > > > > > > > > > > > > > > > > motivating
> > > > > > > > > > > > > > > > > > > > > > these
> > > > > > > > > > > > > > > > > > > > > > > that wouldn't be just as
> > easily
> > > > > > > satisfied
> > > > > > > > > with
> > > > > > > > > > > batch
> > > > > > > > > > > > > > > > operations
> > > > > > > > > > > > > > > > > > > > > (which
> > > > > > > > > > > > > > > > > > > > > > > we
> > > > > > > > > > > > > > > > > > > > > > > seem to have at least for some
> > > > things).
> > > > > > > In
> > > > > > > > > > > terms of
> > > > > > > > > > > > > > > > flexibility
> > > > > > > > > > > > > > > > > > > > > > > Callbacks >
> > > > > > > > > > > > > > > > > > > > > > > Futures > Batch Ops but I
> > think in
> > > > > > > terms of
> > > > > > > > > > > > > usability it
> > > > > > > > > > > > > > > > is the
> > > > > > > > > > > > > > > > > > > > > exact
> > > > > > > > > > > > > > > > > > > > > > > opposite so let's make sure we
> > > > have
> > > > > > > worked
> > > > > > > > > out
> > > > > > > > > > > how
> > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > API will
> > > > > > > > > > > > > > > > > > > be
> > > > > > > > > > > > > > > > > > > > > > used
> > > > > > > > > > > > > > > > > > > > > > > before deciding. In
> > particular I
> > > > think
> > > > > > > java
> > > > > > > > > > > Futures
> > > > > > > > > > > > > are
> > > > > > > > > > > > > > > > often an
> > > > > > > > > > > > > > > > > > > > > > > uncomfortable half-way point
> > since
> > > > > > > calling
> > > > > > > > > > > get() and
> > > > > > > > > > > > > > > > blocking
> > > > > > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > > > > > > thread is
> > > > > > > > > > > > > > > > > > > > > > > often not what you want for
> > > > chaining
> > > > > > > > > sequences
> > > > > > > > > > > of
> > > > > > > > > > > > > > > > operations in
> > > > > > > > > > > > > > > > > > > a
> > > > > > > > > > > > > > > > > > > > > > truly
> > > > > > > > > > > > > > > > > > > > > > > async way, so 99% of people
> > just
> > > > use the
> > > > > > > > > future
> > > > > > > > > > > as
> > > > > > > > > > > > > a way
> > > > > > > > > > > > > > > > to
> > > > > > > > > > > > > > > > > > > batch
> > > > > > > > > > > > > > > > > > > > > > calls.
> > > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > We should definitely figure out how
> > > > the APIs
> > > > > > > are
> > > > > > > > > > > going
> > > > > > > > > > > > > to be
> > > > > > > > > > > > > > > > used
> > > > > > > > > > > > > > > > > > > before
> > > > > > > > > > > > > > > > > > > > > > deciding. I agree that callbacks
> > are
> > > > > > > definitely
> > > > > > > > > > > painful
> > > > > > > > > > > > > and
> > > > > > > > > > > > > > > > there's
> > > > > > > > > > > > > > > > > > > > > little
> > > > > > > > > > > > > > > > > > > > > > reason to expose them in a modern
> > API
> > > > unless
> > > > > > > it's
> > > > > > > > > > > meant
> > > > > > > > > > > > > to be
> > > > > > > > > > > > > > > > very
> > > > > > > > > > > > > > > > > > > low
> > > > > > > > > > > > > > > > > > > > > > level. When it comes to Futures, I
> > > > think it's
> > > > > > > > > > > important
> > > > > > > > > > > > > to
> > > > > > > > > > > > > > > > > > > distinguish
> > > > > > > > > > > > > > > > > > > > > what
> > > > > > > > > > > > > > > > > > > > > > is available in Java 7 and below
> > > > versus what
> > > > > > > is
> > > > > > > > > > > > > available from
> > > > > > > > > > > > > > > > Java 8
> > > > > > > > > > > > > > > > > > > > > > onwards. CompletableFuture makes it
> > > > much
> > > > > > > easier
> > > > > > > > > to
> > > > > > > > > > > > > > > > compose/chain
> > > > > > > > > > > > > > > > > > > > > operations
> > > > > > > > > > > > > > > > > > > > > > (in a similar vein to
> > > > java.util.Stream, our
> > > > > > > own
> > > > > > > > > > > Streams
> > > > > > > > > > > > > API,
> > > > > > > > > > > > > > > > etc.)
> > > > > > > > > > > > > > > > > > > and it
> > > > > > > > > > > > > > > > > > > > > > gives you the ability to register
> > > > callbacks
> > > > > > > if
> > > > > > > > > you
> > > > > > > > > > > > > really want
> > > > > > > > > > > > > > > > to
> > > > > > > > > > > > > > > > > > > > > (avoiding
> > > > > > > > > > > > > > > > > > > > > > the somewhat odd situation in the
> > > > Producer
> > > > > > > where
> > > > > > > > > we
> > > > > > > > > > > > > return a
> > > > > > > > > > > > > > > > Future
> > > > > > > > > > > > > > > > > > > _and_
> > > > > > > > > > > > > > > > > > > > > > allow you to pass a callback).
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > > - Personally I don't think
> > > > splitting the
> > > > > > > > > admin
> > > > > > > > > > > > > methods up
> > > > > > > > > > > > > > > > > > > actually
> > > > > > > > > > > > > > > > > > > > > > makes
> > > > > > > > > > > > > > > > > > > > > > > things more usable. It just
> > makes
> > > > you
> > > > > > > have
> > > > > > > > > to
> > > > > > > > > > > dig
> > > > > > > > > > > > > through
> > > > > > > > > > > > > > > > our
> > > > > > > > > > > > > > > > > > > > > > > hierarchy. I
> > > > > > > > > > > > > > > > > > > > > > > think a flat class with a
> > bunch of
> > > > > > > > > operations
> > > > > > > > > > > (like
> > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > consumer
> > > > > > > > > > > > > > > > > > > > > api)
> > > > > > > > > > > > > > > > > > > > > > is
> > > > > > > > > > > > > > > > > > > > > > > probably the easiest for
> > people
> > > > to grok
> > > > > > > and
> > > > > > > > > find
> > > > > > > > > > > > > things
> > > > > > > > > > > > > > > > on. I am
> > > > > > > > > > > > > > > > > > > > > kind
> > > > > > > > > > > > > > > > > > > > > > > of a
> > > > > > > > > > > > > > > > > > > > > > > dumb PHP programmer at heart,
> > > > though.
> > > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > I am not sure it's fair to compare
> > the
> > > > > > > > > AdminClient
> > > > > > > > > > > with
> > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > > Consumer. The
> > > > > > > > > > > > > > > > > > > > > > former has APIs for a bunch of
> > > > unrelated APIs
> > > > > > > > > > > (topics,
> > > > > > > > > > > > > ACLs,
> > > > > > > > > > > > > > > > configs,
> > > > > > > > > > > > > > > > > > > > > > consumer groups, delegation tokens,
> > > > preferred
> > > > > > > > > leader
> > > > > > > > > > > > > election,
> > > > > > > > > > > > > > > > > > > partition
> > > > > > > > > > > > > > > > > > > > > > reassignment, etc.) where the
> > latter is
> > > > > > > pretty
> > > > > > > > > > > > > specialised.
> > > > > > > > > > > > > > > > For each
> > > > > > > > > > > > > > > > > > > of
> > > > > > > > > > > > > > > > > > > > > the
> > > > > > > > > > > > > > > > > > > > > > resources, you may have 3-4
> > > > operations, it
> > > > > > > will
> > > > > > > > > get
> > > > > > > > > > > > > confusing
> > > > > > > > > > > > > > > > fast.
> > > > > > > > > > > > > > > > > > > Also,
> > > > > > > > > > > > > > > > > > > > > > do you really think an API that
> > has one
> > > > > > > level of
> > > > > > > > > > > > > grouping will
> > > > > > > > > > > > > > > > mean
> > > > > > > > > > > > > > > > > > > that
> > > > > > > > > > > > > > > > > > > > > > users have to "dig through our
> > > > hierarchy"? Or
> > > > > > > > > are you
> > > > > > > > > > > > > > > > concerned that
> > > > > > > > > > > > > > > > > > > once
> > > > > > > > > > > > > > > > > > > > > > we go in that direction, there is a
> > > > danger of
> > > > > > > > > making
> > > > > > > > > > > the
> > > > > > > > > > > > > > > > hierarchy
> > > > > > > > > > > > > > > > > > > more
> > > > > > > > > > > > > > > > > > > > > > complicated?
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > Finally, I am not sure I would use
> > the
> > > > > > > consumer
> > > > > > > > > as an
> > > > > > > > > > > > > example
> > > > > > > > > > > > > > > > of
> > > > > > > > > > > > > > > > > > > > > something
> > > > > > > > > > > > > > > > > > > > > > that is easy to grok. :) The fact
> > that
> > > > > > > methods
> > > > > > > > > behave
> > > > > > > > > > > > > pretty
> > > > > > > > > > > > > > > > > > > differently
> > > > > > > > > > > > > > > > > > > > > > (some are blocking while others
> > only
> > > > have an
> > > > > > > > > effect
> > > > > > > > > > > after
> > > > > > > > > > > > > > > > poll) with
> > > > > > > > > > > > > > > > > > > no
> > > > > > > > > > > > > > > > > > > > > > indication from the type signature
> > or
> > > > naming
> > > > > > > > > > > convention
> > > > > > > > > > > > > makes
> > > > > > > > > > > > > > > > it
> > > > > > > > > > > > > > > > > > > harder,
> > > > > > > > > > > > > > > > > > > > > > not easier, to understand.
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > > > Ismael
> > > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > >
> > > > > > >
> > > >
> >
>
>
>
> --
> *Gwen Shapira*
> Product Manager | Confluent
> 650.450.2760 | @gwenshap
> Follow us: Twitter <https://twitter.com/ConfluentInc> | blog
> <http://www.confluent.io/blog>
