Thank you Ben, I appreciate your answer. I AM using the key to send messages from the selected producer to a selected partition – Q1 covered.
If Q2 seems obscure I could add that I am talking about Java client library and basically asked for clarification to the API doc statement that in case of manual partition assignment consumer failure doesn’t trigger the re-balancing. Does the broker register this failure in any shape or form? Is there a way to notify the application that started consumer thread (in group topic subscription I can subscribe the consumer with a callback that IS called on revocation of ownership) about failure of this thread from broker point of view? Thank you On Wed, Dec 21, 2016 at 6:06 AM, Ben Stopford <b...@confluent.io> wrote: > Hi Alexi > > Typically you would use a key to guarantee that messages with the same key > have a global ordering, rather than using manual assignment. Kafka will > send all messages with the same key to the same partition. If you need > global ordering, spanning all messages from a single producer, you can use > a single partition topic. This will limit you to one active consumer per > consumer group as the consumer group protocol guarantees that a partition > can only be assigned to one consumer, within a group, at one time. > > B > > On Wed, Dec 21, 2016 at 4:36 AM Alexei Levashov < > alexei.levas...@arrayent.com> wrote: > > > Hello, > > I have a few newbie questions about usage of Kafka as a messaging system. > > Kafka version - 0.10.1.0. > > > > 1 - Let's assume that I want to ensure time sequence of events i.e. if > > message A from producer was published at time t1 to partition P and > message > > B from the same producer published to partition P at time t2, > > I want to consume message A before message B, provided t1<t2. > > > > Question1, > > Do I have any choice except one consumer per partition? > > > > 2. - If I have one consumer per partition and use > > consumer.assign(partitionList) call to assign consumer to a partition > do I > > still need group membership for this single consumer? > > I didn't find clear description what is the protocol of interaction > > between GroupCoordinator and PartitionLeader > > < > > https://cwiki.apache.org/confluence/display/KAFKA/ > Kafka+Client-side+Assignment+Proposal > > > > > will be in case of "manual" partition assignment. > > On one hand the API documentation > > < > > https://kafka.apache.org/0101/javadoc/index.html?org/apache/ > kafka/clients/consumer/KafkaConsumer.html > > > > > says > > that : > > "Manual partition assignment does not use group coordination, so > > consumer failures will not cause assigned partitions to be rebalanced. > > Each consumer acts independently even if it shares a groupId with > > another consumer. > > To avoid offset commit conflicts, you should usually ensure that > the > > groupId is unique for each consumer instance." > > > > On the other hand I am still consuming messages in > > consumer.poll(timeout) loop and inside this poll() call consumer should > > send heartbeats to coordinator. > > > > Question 2 . > > If consumer doesn't send these heartbeats for [*session.timeout.ms > > <http://session.timeout.ms>*] period of time should the partition > > ownership be revoked or not? > > > > If no - does it mean I have to use homegrown heartbeats for consumer > > state monitoring? How would the application know that the consumer thread > > is dead? > > If yes - what callback to notify the application can I use? > > ConsumerRebalanceListener is available only for group subscription. > > > > Thank you. > > >
