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> > > ********************************************/ > > >
