We're using Kafka streams to write data to a sink topic. I'm running an avro-consumer command line to check if there's data in the sink topic:
bin/kafka-avro-console-consumer --topic sink.output.topic --from-beginning --new-consumer --bootstrap-server
I see data when I simultaneously run the consumer while kafka streams application is running but if I stop the consumer and run again after a few minutes, I don't see any data. Few possibilities:
1) Is this because the kafka streams is wiping out the records from the output topic every time it pushes records to sink?
2) Or is this just a consumer related issue?
I believe that this is because --from-beginning is used only when consumer didn't establish offset yet. Have you tried to use --offset earliest instead?
From you description issues seems to be with the retention time.
data might have removed when you run 2nd time.
you can configure the retention time
Example : log.retention.hours=168
Related
Kafka Quickstart
Using Kafka v2.1.0 on RHEL v6.9
Consumer fails to receive data when one of the Kafka brokers is down.
Steps performed:
1. Start zookeeper
2. Start Kafka-Server0 (localhost:9092, kafkalogs1)
3. Start Kafka-Server1 (localhost:9094, kafkalog2)
4. Create topic "test1", num of partitions = 1, replication factor = 2
5. Run producer for topic "test1"
6. Run consumer
7. Send messages from the producer
8. Receive messages on the consumer side.
All the above steps worked without any issues.
When I shutdown Kafka-Server0, the consumer stops getting data from Producer.
When I bring back up Kafka-Server0, the consumer starts to get messages from where it left off.
These are the commands used
bin/kafka-console-producer.sh --broker-list localhost:9092 --topic test1
bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic test1
bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 2 --partitions 1 --topic test1
The behavior is the same (no message received on the consumer side) when I run the consumer with two servers specified in the --bootstrap-server option.
bin/kafka-console-consumer.sh --bootstrap-server localhost:9092,localhost:9094 --topic test1
Any idea why the consumer stops getting messages when server0 is down even though the replication factor for the topic test1 was set to 2?
There is a similar question already but it was not answered completely
Kafka 0.10 quickstart: consumer fails when "primary" broker is brought down
If the offsets topic is unavailable, you cannot consume.
Look at the server.properties file for these, and see the comment above, and increase accordingly (only applies if topic doesn't already exist)
# The replication factor for the group metadata internal topics "__consumer_offsets" and "__transaction_state"
# For anything other than development testing, a value greater than 1 is recommended for to ensure availability such as 3.
offsets.topic.replication.factor=1
transaction.state.log.replication.factor=1
According to your previous question, looks like it only has one replica
See how you can increase replication factor for an existing topic
In initial versions of Kafka, offset was being managed at zookeeper, but Kafka has continuously evolved over the time introducing lot of new features. Now Kafka manages the offset in a topic __consumer_offsets.
You can think of a scenario where you created a topic with a replication factor of 1. In case the broker goes down the data is only on that Kafka node which is down. So you can't get this data. Same analogy applies to __consumer_offsets topic.
You need to revisit the server.properties in order to get features you are expecting. But in case you still wanna consume the messages from the replica partition, you may need to re-start the console consumer with --from-beginning true
Is it possible to remove data from Kafka after that data consumed?
I am using Kafka and Zookeeper combined to exchange some data between 2 nodes. I am having trouble with memory of Kafka because I am inserting so many data. In this way I need to clean datas from Kafka after I consumed them. Is it possible?
You can try out changing the retention time.
kafka-topics.sh --zookeeper localhost:13003 --alter --topic MyTopic --config retention.ms=1000
But be sure, as the message will be deleted irrespective of weather it is consumed or not.
The topics that I had started yesterday are not having any data. The topics appear in the list command but all data is lost. The data was produced and saved in the topic. However, after a period that I dont know, the data is gone. It should be noted that I did consume the data once.
How?
What settings should I change?
If you are trying to consumer using the same consumer group and that group's offsets are not expired yet then you will not get anything back.
If you are not consuming as part of the same consumer group, perhaps topic data is expired and deleted?
You can check the start and end offset of topic; e.g.
bin/kafka-run-class.sh kafka.tools.GetOffsetShell --broker-list localhost:9092 --topic test-orders --time -2
bin/kafka-run-class.sh kafka.tools.GetOffsetShell --broker-list localhost:9092 --topic test-orders --time -1
If reported start and end offsets match there is no data in the topic. In that case, you can take a look at retention.ms at topic or broker level. Increasing the value of this config would keep the records longer at the expense of using additional disk space.
I've spent some hours to figure out what was going on but didn't manage to find the solution.
Here is my set up on a single machine:
1 zookeeper running
3 broker running (on port 9092/9093/9094)
1 topic with 3 partitions and 3 replications (each partition are properly assigned between brokers)
I'm using kafka console producer to insert messages. If i check the replication offset (cat replication-offset-checkpoint), I see that my messages are properly ingested by Kafka.
Now I use the kafka console consumer (new):
sudo bin/kafka-console-consumer.sh --bootstrap-server localhost:9092 --from-beginning --topic testTopicPartitionned2
I dont see anything consumed. I tried to delete my logs folder (/tmp/kafka-logs-[1,2,3]), create new topics, still nothing.
However when I use the old kafka consumer:
sudo bin/kafka-console-consumer.sh --zookeeper localhost:2181 --topic testTopicPartitionned2
I can see my messages.
Am I missing something big here to make this new consumer work ?
Thanks in advance.
Check to see what setting the consumer is using for auto.offset.reset property
This will affect what a consumer group without a previously committed offset will do in terms of setting where to start reading messages from a partition.
Check the Kafka docs for more on this.
Try providing all your brokers to --bootstrap-server argument to see if you notice any differnce:
sudo bin/kafka-console-consumer.sh --bootstrap-server localhost:9092,localhost:9093,localhost:9094 --from-beginning --topic testTopicPartitionned2
Also, your topic name is rather long. I assume you've already made sure you provide the correct topic name.
I try to read messages in kafka consumer using the following command:
bin/kafka-console-consumer.sh --zookeeper localhost:2181 --topic test --from-beginning
Here we can read old messages of about 4 days as we have set retention time in kafka server configuration file as 7 days. But while we are trying to read messages using KafkaConsumer of kaka-python client library like following:
cons = KafkaConsumer("localhost:9092", "test","smallest")
cons.fetch_messages()
we are getting messages of today's only with some offset. I don't have any idea how to get oldest message available in Kafka like we got in kafka consumer shell script above. Please help.
The docs show the config passed in via namedtuples.
consumer = KafkaConsumer('topic1', 'topic2',
bootstrap_servers=['localhost:9092'],
group_id='my_consumer_group',
auto_commit_enable=True,
auto_commit_interval_ms=30 * 1000,
auto_offset_reset='smallest')