Hey Jens, The heartbeat response is used by the coordinator to tell group members that the group needs to rebalance. For example, if a new member joins the consumer group, then the coordinator will wait for the heartbeat from each member and set a REBALANCE_NEEDED error code in the response. Hence the approximate time to rebalance depends on the heartbeat interval. This is why we have set it fairly low by default. We actually had the interval based on the session timeout initially (we set it to 1/3 of the session timeout), but during development, it seemed like a good idea to give users more control over the rebalance overhead by controlling the heartbeat interval. For example, if you need to set the session timeout to 120 seconds, you might not be too thrilled to have your best-case rebalance time of about 40 seconds.
-Jason On Mon, Feb 8, 2016 at 7:49 AM, Jens Rantil <jens.ran...@tink.se> wrote: > Hi again, > > A somewhat related question is also how the heartbeat interval and session > timeout relates to the poll timeout. Must the poll timeout always be lower > than the heartbeat interval? > > Cheers, > Jens > > On Monday, February 8, 2016, Jens Rantil <jens.ran...@tink.se> wrote: > > > Hi, > > > > I am trying to wrap my head around the difference between " > > session.timeout.ms" and "heartbeat.interval.ms". Clearly they are > > somewhat tied to the same logic since heartbeat value should be less than > > 1/3 of the session timeout. > > > > Let me add some specific questions: > > > > - Will a session be considered "dead" if it hasn't received a > > heartbeat within "session.timeout.ms"? In that case giving > 2*heartbeat > > as slack for missed heartbeats seem like a LOT of slack. Given the > default > > values, a client will have 27 seconds(!) to be able to send a second > > heartbeat. > > - Why can't session timeout simply be based on heartbeat interval? > > > > Could anyone clarify this a bit? Also, if you are writing a new consumer, > > what is your reasoning when setting these two value? > > > > Thanks, > > Jens > > > > > > -- > > Jens Rantil > > Backend engineer > > Tink AB > > > > Email: jens.ran...@tink.se > > <javascript:_e(%7B%7D,'cvml','jens.ran...@tink.se');> > > Phone: +46 708 84 18 32 > > Web: www.tink.se > > > > Facebook <https://www.facebook.com/#!/tink.se> Linkedin > > < > http://www.linkedin.com/company/2735919?trk=vsrp_companies_res_photo&trkInfo=VSRPsearchId%3A1057023381369207406670%2CVSRPtargetId%3A2735919%2CVSRPcmpt%3Aprimary > > > > Twitter <https://twitter.com/tink> > > > > > > -- > Jens Rantil > Backend engineer > Tink AB > > Email: jens.ran...@tink.se > Phone: +46 708 84 18 32 > Web: www.tink.se > > Facebook <https://www.facebook.com/#!/tink.se> Linkedin > < > http://www.linkedin.com/company/2735919?trk=vsrp_companies_res_photo&trkInfo=VSRPsearchId%3A1057023381369207406670%2CVSRPtargetId%3A2735919%2CVSRPcmpt%3Aprimary > > > Twitter <https://twitter.com/tink> >
