Newbie here, Q2) Think, there is no rebalance if you go with manual partition assignment (assign(List) <https://kafka.apache.org/090/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#assign%28java.util.List%29>), but were you looking for subscribe(List, ConsumerRebalanceListener) <https://kafka.apache.org/090/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#subscribe%28java.util.List,%20org.apache.kafka.clients.consumer.ConsumerRebalanceListener%29> to notify on rebalance to cleanup? Don't think you can do both, see here: https://kafka.apache.org/090/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#assign(java.util.List) where it mentions that it is not possible to use both manual partition assignment and group assignment, but, I do wonder what happens if consumers do different approaches?
Other consumer related exceptions can still happen. And unlike Producer callback, don't think there is a callback other than try/catch for example in poll, commit, and other calls. I could not find the best way to recover/continue from these (non rebalance) exceptions other than retry. https://kafka.apache.org/090/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#poll(long) https://kafka.apache.org/090/javadoc/org/apache/kafka/common/errors/package-frame.html On Wed, Dec 21, 2016 at 2:32 PM, Alexei Levashov < alexei.levas...@arrayent.com> wrote: > 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. > > > > > > -- Radha Krishna, Proddaturi 253-234-5657
