@Guozhang: Thanks for your comments, I've answered some of those. The main thing is having merged request for create-alter-delete-describe - I have some concerns about this approach.
@*Jay*: I see that introduced ClusterMetadaRequest is also one of the concerns. We can solve it if we implement re-routing facility. But I agree with Guozhang - it will make clients' internals a little bit easier but this seems to be a complex logic to implement and support then. Especially for Fetch and Produce (even if we add re-routing later for these requests). Also people will tend to avoid this re-routing facility and hold local cluster cache to ensure their high-priority requests (which some of the admin requests are) not sent to some busy broker where they wait to be routed to the correct one. As pointed out by Jun here ( https://issues.apache.org/jira/browse/KAFKA-1772?focusedCommentId=14234530&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14234530) to solve the issue we might introduce a message type to get cluster state. But I agree we can just update TopicMetadataResponse to include controllerId (and probably smth else). What are you thougths? Thanks, Andrii On Thu, Feb 12, 2015 at 8:31 AM, Guozhang Wang <wangg...@gmail.com> wrote: > I think for the topics commands we can actually merge > create/alter/delete/describe as one request type since their formats are > very much similar, and keep list-topics and others like > partition-reassignment / preferred-leader-election as separate request > types, I also left some other comments on the RB ( > https://reviews.apache.org/r/29301/). > > On Wed, Feb 11, 2015 at 2:04 PM, Jay Kreps <jay.kr...@gmail.com> wrote: > > > Yeah I totally agree that we don't want to just have one "do admin stuff" > > command that has the union of all parameters. > > > > What I am saying is that command line tools are one client of the > > administrative apis, but these will be used in a number of scenarios so > > they should make logical sense even in the absence of the command line > > tool. Hence comments like trying to clarify the relationship between > > ClusterMetadata and TopicMetadata...these kinds of things really need to > be > > thought through. > > > > Hope that makes sense. > > > > -Jay > > > > On Wed, Feb 11, 2015 at 1:41 PM, Andrii Biletskyi < > > andrii.bilets...@stealth.ly> wrote: > > > > > Jay, > > > > > > Thanks for answering. You understood correctly, most of my comments > were > > > related to your point 1) - about "well thought-out" apis. Also, yes, > as I > > > understood we would like to introduce a single unified CLI tool with > > > centralized server-side request handling for lots of existing ones > (incl. > > > TopicCommand, CommitOffsetChecker, ReassignPartitions, smth else if > added > > > in future). In our previous discussion ( > > > https://issues.apache.org/jira/browse/KAFKA-1694) people said they'd > > > rather > > > have a separate message for each command, so, yes, this way I came to > 1-1 > > > mapping between commands in the tool and protocol additions. But I > might > > be > > > wrong. > > > At the end I just try to start discussion how at least generally this > > > protocol should look like. > > > > > > Thanks, > > > Andrii > > > > > > On Wed, Feb 11, 2015 at 11:10 PM, Jay Kreps <jay.kr...@gmail.com> > wrote: > > > > > > > Hey Andrii, > > > > > > > > To answer your earlier question we just really can't be adding any > more > > > > scala protocol objects. These things are super hard to maintain > because > > > > they hand code the byte parsing and don't have good versioning > support. > > > > Since we are already planning on converting we definitely don't want > to > > > add > > > > a ton more of these--they are total tech debt. > > > > > > > > What does it mean that the changes are isolated from the current code > > > base? > > > > > > > > I actually didn't understand the remaining comments, which of the > > points > > > > are you responding to? > > > > > > > > Maybe one sticking point here is that it seems like you want to make > > some > > > > kind of tool, and you have made a 1-1 mapping between commands you > > > imagine > > > > in the tool and protocol additions. I want to make sure we don't do > > that. > > > > The protocol needs to be really really well thought out against many > > use > > > > cases so it should make perfect logical sense in the absence of > knowing > > > the > > > > command line tool, right? > > > > > > > > -Jay > > > > > > > > On Wed, Feb 11, 2015 at 11:57 AM, Andrii Biletskyi < > > > > andrii.bilets...@stealth.ly> wrote: > > > > > > > > > Hey Jay, > > > > > > > > > > I would like to continue this discussion as it seem there is no > > > progress > > > > > here. > > > > > > > > > > First of all, could you please explain what did you mean in 2? How > > > > exactly > > > > > are we going to migrate to the new java protocol definitions. And > why > > > > it's > > > > > a blocker for centralized CLI? > > > > > > > > > > I agree with you, this feature includes lots of stuff, but > thankfully > > > > > almost all changes are isolated from the current code base, > > > > > so the main thing, I think, we need to agree is RQ/RP format. > > > > > So how can we start discussion about the concrete messages format? > > > > > Can we take ( > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-4+-+Command+line+and+centralized+administrative+operations#KIP-4-Commandlineandcentralizedadministrativeoperations-ProposedRQ/RPFormat > > > > > ) > > > > > as starting point? > > > > > > > > > > We had some doubts earlier whether it worth introducing one generic > > > Admin > > > > > Request for all commands ( > > > > https://issues.apache.org/jira/browse/KAFKA-1694 > > > > > ) > > > > > but then everybody agreed it would be better to have separate > message > > > for > > > > > each admin command. The Request part is really dictated from the > > > command > > > > > (e.g. TopicCommand) arguments itself, so the proposed version > should > > be > > > > > fine (let's put aside for now remarks about Optional type, > batching, > > > > > configs normalization - I agree with all of them). > > > > > So the second part is Response. I see there are two cases here. > > > > > a) "Mutate" requests - Create/Alter/... ; b) "Get" requests - > > > > > List/Describe... > > > > > > > > > > a) should only hold request result (regardless what we decide about > > > > > blocking/non-blocking commands execution). > > > > > Usually we provide error code in response but since we will use > this > > in > > > > > interactive shell we need some human readable error description - > so > > I > > > > > added errorDesription field where you can at least leave > > > > > exception.getMessage. > > > > > > > > > > b) in addition to previous item message should hold command > specific > > > > > response data. We can discuss in detail each of them but let's for > > now > > > > > agree about the overall pattern. > > > > > > > > > > Thanks, > > > > > Andrii Biletskyi > > > > > > > > > > On Fri, Jan 23, 2015 at 6:59 AM, Jay Kreps <jay.kr...@gmail.com> > > > wrote: > > > > > > > > > > > Hey Joe, > > > > > > > > > > > > This is great. A few comments on KIP-4 > > > > > > > > > > > > 1. This is much needed functionality, but there are a lot of the > so > > > > let's > > > > > > really think these protocols through. We really want to end up > > with a > > > > set > > > > > > of well thought-out, orthoganol apis. For this reason I think it > is > > > > > really > > > > > > important to think through the end state even if that includes > APIs > > > we > > > > > > won't implement in the first phase. > > > > > > > > > > > > 2. Let's please please please wait until we have switched the > > server > > > > over > > > > > > to the new java protocol definitions. If we add upteen more ad > hoc > > > > scala > > > > > > objects that is just generating more work for the conversion we > > know > > > we > > > > > > have to do. > > > > > > > > > > > > 3. This proposal introduces a new type of optional parameter. > This > > is > > > > > > inconsistent with everything else in the protocol where we use -1 > > or > > > > some > > > > > > other marker value. You could argue either way but let's stick > with > > > > that > > > > > > for consistency. For clients that implemented the protocol in a > > > better > > > > > way > > > > > > than our scala code these basic primitives are hard to change. > > > > > > > > > > > > 4. ClusterMetadata: This seems to duplicate TopicMetadataRequest > > > which > > > > > has > > > > > > brokers, topics, and partitions. I think we should rename that > > > request > > > > > > ClusterMetadataRequest (or just MetadataRequest) and include the > id > > > of > > > > > the > > > > > > controller. Or are there other things we could add here? > > > > > > > > > > > > 5. We have a tendency to try to make a lot of requests that can > > only > > > go > > > > > to > > > > > > particular nodes. This adds a lot of burden for client > > > implementations > > > > > (it > > > > > > sounds easy but each discovery can fail in many parts so it ends > up > > > > > being a > > > > > > full state machine to do right). I think we should consider > making > > > > admin > > > > > > commands and ideally as many of the other apis as possible > > available > > > on > > > > > all > > > > > > brokers and just redirect to the controller on the broker side. > > > Perhaps > > > > > > there would be a general way to encapsulate this re-routing > > behavior. > > > > > > > > > > > > 6. We should probably normalize the key value pairs used for > > configs > > > > > rather > > > > > > than embedding a new formatting. So two strings rather than one > > with > > > an > > > > > > internal equals sign. > > > > > > > > > > > > 7. Is the postcondition of these APIs that the command has begun > or > > > > that > > > > > > the command has been completed? It is a lot more usable if the > > > command > > > > > has > > > > > > been completed so you know that if you create a topic and then > > > publish > > > > to > > > > > > it you won't get an exception about there being no such topic. > > > > > > > > > > > > 8. Describe topic and list topics duplicate a lot of stuff in the > > > > > metadata > > > > > > request. Is there a reason to give back topics marked for > > deletion? I > > > > > feel > > > > > > like if we just make the post-condition of the delete command be > > that > > > > the > > > > > > topic is deleted that will get rid of the need for this right? > And > > it > > > > > will > > > > > > be much more intuitive. > > > > > > > > > > > > 9. Should we consider batching these requests? We have generally > > > tried > > > > to > > > > > > allow multiple operations to be batched. My suspicion is that > > without > > > > > this > > > > > > we will get a lot of code that does something like > > > > > > for(topic: adminClient.listTopics()) > > > > > > adminClient.describeTopic(topic) > > > > > > this code will work great when you test on 5 topics but not do as > > > well > > > > if > > > > > > you have 50k. > > > > > > > > > > > > 10. I think we should also discuss how we want to expose a > > > programmatic > > > > > JVM > > > > > > client api for these operations. Currently people rely on > > AdminUtils > > > > > which > > > > > > is totally sketchy. I think we probably need another client under > > > > > clients/ > > > > > > that exposes administrative functionality. We will need this just > > to > > > > > > properly test the new apis, I suspect. We should figure out that > > API. > > > > > > > > > > > > 11. The other information that would be really useful to get > would > > be > > > > > > information about partitions--how much data is in the partition, > > what > > > > are > > > > > > the segment offsets, what is the log-end offset (i.e. last > offset), > > > > what > > > > > is > > > > > > the compaction point, etc. I think that done right this would be > > the > > > > > > successor to the very awkward OffsetRequest we have today. > > > > > > > > > > > > -Jay > > > > > > > > > > > > On Wed, Jan 21, 2015 at 10:27 PM, Joe Stein < > joe.st...@stealth.ly> > > > > > wrote: > > > > > > > > > > > > > Hi, created a KIP > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-4+-+Command+line+and+centralized+administrative+operations > > > > > > > > > > > > > > JIRA https://issues.apache.org/jira/browse/KAFKA-1694 > > > > > > > > > > > > > > /******************************************* > > > > > > > Joe Stein > > > > > > > Founder, Principal Consultant > > > > > > > Big Data Open Source Security LLC > > > > > > > http://www.stealth.ly > > > > > > > Twitter: @allthingshadoop < > > http://www.twitter.com/allthingshadoop > > > > > > > > > > > ********************************************/ > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > -- Guozhang >
