The ack method only affects the producer. With acks=0 or 1, HW advancement is done asynchronously with the producer, so the leader will continue to accept writes regardless of follower status. Only if you have acks=all and min ISR set to the replication factor will your acks be synchronous with the HW.
If you are producing to a topic partition that is under-replicated, your settings determine whether new data can be written to it or not. -- Peter (from phone) > On Oct 8, 2019, at 8:31 AM, Isuru Boyagane <isuruboyagane...@cse.mrt.ac.lk> > wrote: > > Hi Peter, > > Okay. Then, whatever the producer acks configuration is, Leader replica > waits for *all* other follower replicas to persist the message before > advancing HW(without considering the *current ISR* set)? > > Thanks > >> On Tue, 8 Oct 2019 at 14:54, Peter Bukowinski <pmb...@gmail.com> wrote: >> >> The behavior of the high water mark is independent of producer ack >> settings. It is a property of topic partitions only. (Remember that >> multiple producers with different configurations can write to the same >> topic.) The high water mark advances to the latest offset that exists in >> all topic partition replicas. If your topic has a replication factor of 3, >> then a partition’s HW will only advance toward the LEO after both replicas >> are in sync with the leader. >> >> min.insync.replicas controls how many replicas must be in sync when your >> producer in using acks=all. This does not affect consumers. >> >> HW does affect consumers, since data between the HW and LEO cannot be >> consumed yet. >> >> -- >> Peter >> >>> On Oct 8, 2019, at 12:35 AM, Isuru Boyagane < >> isuruboyagane...@cse.mrt.ac.lk> wrote: >>> >>> Hi, >>> >>> 4 >>> >>> I read about the Kafka replication protocol. I found that Kafka maintains >>> LEO and HW. As I understood, >>> >>> LEO: Offset of latest message a replica has seen. >>> >>> HW: Offset of the latest message which is guaranteed that each replica >> has >>> persisted into their local log. >>> >>> We can set the following acknowledgement methods in Kafka producers >>> configurations. >>> >>> >>> 1. acks = 0 (Leader replica sends an acknowledgement to the producer >>> once it has seen the message) >>> 2. acks = 1 (Leader replica sends an acknowledgement to the producer >>> once it has persisted the message to its local log) >>> 3. acks = all (Leader replica sends an acknowledgement to the >>> producer once every in-sync replica has persisted the message to >>> its local >>> log) >>> >>> So my question is how the leader advances the HW depending on the >>> acknowledgement method message producer uses. >>> >>> What I think is, >>> >>> 1. >>> >>> for acks = 0, Leader advances the HW when it sees a new message. >>> 2. >>> >>> for acks = 1, Leader advances the HW when it has written the new >> message >>> to its local log. >>> 3. >>> >>> for acks = all, Leader advances HW when each an every follower sent ack >>> that they persisted the message. >>> >>> Is this correct? Can anyone clarify this? >>> >>> Thanks >> > > > -- > isuru
