We could able to insert data to kafka using kafka producer API and offset got incremented as well could able to consume data using kafka consumer API and consumer offset got incremented.
But sometimes, Offset was not working properly in the process of push and consume data from kafka. Please help me out.
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I new to Kafka and i have a configuration where i have a source Kafka topic which has messages with a default retention for 7 days. I have 3 brokers with 1 partition and 1 replication.
When i try to consume messages from source Kafka topic and to my target Kafka topic i was able to consume messages in the same order. Now my question is if i am trying to reprocess all the messages from my source Kafka and consume in ,y Target Kafka i see that my Target Kafka is not consuming any messages. I know that duplication should be avoided but lets say i have a scenario where i have 100 messages in my source Kafka and i am expecting 200 messages in my target Kafka after running it twice. But i am just getting 100 messages in my first run and my second run returns nothing.
Can some one please explain why this is happening and what is the functionality behind it ?
Kafka consumer reads data from a partition of a topic. One consumer can read from one partition at one time only.
Once a message has been read by the consumer, it can't be re-read again. Let me first explain the current offset. When we call a poll method, Kafka sends some messages to us. Let us assume we have 100 records in the partition. The initial position of the current offset is 0. We made our first call and received 100 messages. Now Kafka will move the current offset to 100.
The current offset is a pointer to the last record that Kafka has already sent to a consumer in the most recent poll and that has been committed. So, the consumer doesn't get the same record twice because of the current offset. Please go through the following diagram and URL for complete understanding.
https://www.learningjournal.guru/courses/kafka/kafka-foundation-training/offset-management/
When I have a kafka console producer message produce some messages and then start a consumer, I am not getting the messages.
However i am receiving message produced by the producer after a consumer has been started.Should Kafka consumers be started before producers?
--from- beginning seems to give all messages including ones that are consumed.
Please help me with this on both console level and java client example for starting producer first and consuming by starting a consumer.
Kafka stores messages for a configurable amount of time. Default is a week. Consumers do not need to be "available" to receive messages, but they do need to know where they should start reading from
The console consumer has the default option of looking at the latest offset for all partitions. So if you're not actively producing data you see nothing as a consumer. You can specify a group flag for the console consumer or a Java client, and that's what tracks what offsets are read within the Kafka protocol and where a read request will resume from if you stopped that consumer in a group
Otherwise, I think you can only give an offset along with a single partition to consume from
I forwarded few events to Kafka and started my Kafka stream program. My program started processing the events and completed. After some time I stopped my Kafka stream application and I started again. Observed that My Kafka stream program is processing the already processed previous events.
As per my understanding, Kafka stream internally maintains the offset for input topics itself per application id. But here reprocessing the already processed events.
How to verify up to which offset Kafka stream processing was done? How Kafka stream persisted these bookmarks? On what basis & from which Kafka offset, Kafka stream will start read the events from Kafka?
If Kafka steam throws exceptions then is it reprocessed already processed events?
Please clarify my doubts.
Please help me to under stand more.
Kafka Streams internally uses a KafkaConsumer and all running instances form a consumer group using application.id as group.id. Offsets are committed to the Kafka cluster in regular intervals (configurable). Thus, on restart with the same application.id Kafka Streams should pick up the latest committed offset and continue processing from there.
You can check committed offset as for any other consumer group using bin/kafka-consumer-groups.sh tool.
We are using kafka Topology forward to send a record to a kafka topic.
We were using a separate producer to publish the message earlier and we were able to grab the offset and partition of the message. Now we want to replace it with Context.forward.
How can we get the offset and partition of the record sent by Kafka Sink Processor using context.forward
Publish message to topic in producer.type=sync mode. when you call send() method, it will return all the details you are looking.
We have a requirement that the consumer should be able to go back to any point of message stream and reprocess the message.
It looks like to set an offset in High level consumer as it needs setting offset in the zookeeper and re-start of consumer is needed.
Simple consumer supports this ,but need to handle broker leader election ,broker leader failure etc.
The new consumer api provide this ,but it looks like this is still in beta.
So we might have to select simple consumer. Any know issues with simple consumers