http://www.confluent.io/blog/hands-free-kafka-replication-a-lesson-in-operational-simplicity/
From my understanding, the watermark will not advance until both failed follow-broker recovered and caught up. -Matthias On 07/01/2016 12:17 PM, Vikas Kumar wrote: > Hi, > > I have a question about handling of uncommitted messages in Kafka. > > Lets say the partition has 4 replicas (1 leader, 3 followers) and all are > currently in sync. min.insync.replicas is set to 3 and > request.required.acks is set to all or -1. > > The producer send a message to the leader, the leader appends it to it's > log. After that, two of the replicas crashed before they could fetch this > message. One remaining replica successfully fetched the message and > appended to it's own log. > > The leader, after certain timeout, will send an error (NotEnoughReplicas, I > think) to the producer since min.insync.replicas condition is not met. > > My question is: what will happen to the message which was appended to > leader and one of the replica's log? > > Will it be delivered to the consumers when crashed replicas come back > online and broker starts accepting and committing new messages (i.e. high > watermark is forwarded in the log)? >
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