Hi, On Tue, 1 Aug 2017 at 08:34 Debasish Ghosh <ghosh.debas...@gmail.com> wrote:
> Hi - > > I have a Kafka Streams application that needs to run on multiple instances. > It fetches metadata from all local stores and has an http query layer for > interactive queries. In some cases when I have new instances deployed, > store migration takes place making the current metadata invalid. Here are > my questions regarding some of the best practices to be followed to handle > this issue of store migration - > > - When the migration is in process, a query for the metadata may result > in InvalidStateStoreException - is it a good practice to always have a > retry semantics based query for the metadata ? > Yes. Whenever the application is rebalancing the stores will be unavailable, so retrying is the right thing to do. > - Should I check KafkaStreams.state() and only assume that I have got > the correct metadata when the state() call returns Running. If it > returns Rebalancing, then I should re-query. Is this correct approach ? > Correct again! If the state is rebalancing, then the metadata (for some stores at least) is going to change, so you should get it again. You can set a StateListener on the KafkaStreams instance to listen to these events. > > regards. > > -- > Debasish Ghosh > http://manning.com/ghosh2 > http://manning.com/ghosh > > Twttr: @debasishg > Blog: http://debasishg.blogspot.com > Code: http://github.com/debasishg >
