Hi, recently our team had try to upgrade kafka 0.10.0.1 to 2.2.0.we do so by upgrade guide http://kafka.apache.org/documentation.html#upgrade, after we set all brokers inter.broker.protocol.version to 2.2.0,we found that producer produce rate become very slow and many messages take more than 500ms(even 1s,2s) to execute send method. we try to add max.in.flight.requests.per.connection,batch.size params,but no use. because document said "Once the brokers begin using the latest protocol version, it will no longer be possible to downgrade the cluster to an older version.",so we have to start another kafka cluster and lose some messages. after that end,i try to upgrade a test cluster has 2 borkers and version is 0.10.0.1, up to 2.2.0,and i change inter.broker.protocol.version from 0.10.0.1 to 2.2.0,and then downgrade to 0.10.0.1 ,i found producer and consumer hasn't any error during whole procedure. so now i have 2 questions: 1.Is there some tips that why our producer send rate become slow? 2.Is it really that inter.broker.protocol.version couldn't downgrade?Or when we couldnt do so?
thx..