Hi Javier, I apologize, I don't think I am making myself clear. I am attempting to get all the tuples for a given key sent to the same Bolt 2 executor instance. I previously followed the pattern of using fieldsGrouping on Bolt1 as this is a well-established pattern. However, there are roughly 4 times as many Bolt 1 executors to every Bolt 2 executor, and I was finding the throughput was very low between Bolts 1 and 2. Once I switched to localOrShuffleGrouping between Bolt 1 and Bolt 2, the throughput tripled. I did this based upon advice from this board to do localOrShuffleGrouping for large fan-in patterns like this (great advice, definitely worked great!).
Unfortunately, this also means that there is no guarantee that all tuples for a given key will be sent to the same Bolt 2. To hopefully get the best of both worlds, I am thinking I can do the fieldsGrouping between KafkaSpout and Bolt 1, and therefore I get the same effect of all tuples for a given key going to the same Bolt 2. Of course, the key (pun intended) is that there is one Bolt 2 per worker, which will ensure all tuples for the same key will go to the same Bolt 1 which will then forward 'em to Bolt 2. Please confirm if this seems logical and that it should work. I think it should, but I may be missing something. Thanks! :) --John On Mon, Oct 5, 2015 at 9:20 AM, Javier Gonzalez <[email protected]> wrote: > If I'm reading this correctly, I think you're not getting the result you > want - having all tuples with a given key processed in the same bolt2 > instance. > > If you want to have all messages of a given key to be processed in the > same Bolt2, you need to do fields grouping from bolt1 to bolt2. By doing > fields grouping in the spout-bolt1 hop and shuffle/local in the bolt1-bolt2 > hop, you're ensuring that bolt1 instances always see the same key, but is > there any guarantee that the bolt2 you want is the nearest/only local bolt > available to any given instance of bolt1? > > Regards, > Javier > On Oct 5, 2015 7:33 AM, "John Yost" <[email protected]> wrote: > >> Hi Everyone, >> >> I am currently prototyping FieldsGrouping at the KafkaSpout vs Bolt >> level. I am curious as to whether anyone else has tried this and, if so, >> how well this worked. >> >> The reason I am attempting to do FieldsGrouping in the KafkaSpout is that >> I moved from fieldsGrouping to localOrShuffleGrouping between Bolt 1 and >> Bolt 2 in my topology due to a 4 to 1 fan in from Bolt 1 to Bolt 2 (for >> example, 200 Bolt 1 executors and 50 Bolt 2 executors) which was >> dramatically slowing throughput. It is still highly preferable to do >> fieldsGrouping one way or another so that I am getting all values for a >> given key to the same Bolt 2 executor, which is the impetus for attempting >> to do fieldsGrouping in the KafkaSpout. >> >> If anyone has any thoughts on this approach, I'd very much like to get >> your thoughts. >> >> Thanks >> >> --John >> >
