@wangguozhang，could you give me some advices.
> 在 2016年9月22日，下午6:56，Kafka <kafka...@126.com> 写道：
>
> Hi all,
> in terms of topic， we create a topic with 6 partition，and each with 3
> replicas.
> in terms of producer，when we send message with ack -1 using sync
> interface.
> in terms of brokers，we set min.insync.replicas to 2.
>
> after we review the kafka broker’s code，we know that we send a message to
> broker with ack -1, then we can get response if ISR of this partition is
> great than or equal to min.insync.replicas，but what confused
> me is replicas in ISR is not strongly consistent，in kafka 0.9 we use
> replica.lag.time.max.ms param to judge whether to shrink ISR, and the
> defaults is 10000 ms, so replicas’ data in isr can lag 10000ms at most,
> we we restart broker which own this partitions’ leader, then controller will
> start a new leader election, which will choose the first replica in ISR that
> not equals to current leader as new leader, then this will loss data.
>
>
> The main produce handle code shows below:
> val numAcks = curInSyncReplicas.count(r => {
> if (!r.isLocal)
> if (r.logEndOffset.messageOffset >= requiredOffset) {
> trace("Replica %d of %s-%d received offset
> %d".format(r.brokerId, topic, partitionId, requiredOffset))
> true
> }
> else
> false
> else
> true /* also count the local (leader) replica */
> })
>
> trace("%d acks satisfied for %s-%d with acks = -1".format(numAcks,
> topic, partitionId))
>
> val minIsr = leaderReplica.log.get.config.minInSyncReplicas
>
> if (leaderReplica.highWatermark.messageOffset >= requiredOffset ) {
> /*
> * The topic may be configured not to accept messages if there are
> not enough replicas in ISR
> * in this scenario the request was already appended locally and then
> added to the purgatory before the ISR was shrunk
> */
> if (minIsr <= curInSyncReplicas.size) {
> (true, ErrorMapping.NoError)
> } else {
> (true, ErrorMapping.NotEnoughReplicasAfterAppendCode)
> }
> } else
> (false, ErrorMapping.NoError)
>
>
> why only logging unAcks and not use numAcks to compare with minIsr, if
> numAcks is 0, but curInSyncReplicas.size >= minIsr, then this will return, as
> ISR shrink procedure is not real time, does this will loss data after leader
> election?
>
> Feedback is greatly appreciated. Thanks.
> meituan.inf
>
>
>
