We had a similar issue and it turns out the flink kafka connector doesn’t honor the groupID. This resulted in multiple consumers getting partial events (basically
load balanced between my multiple consumers).
See
https://stackoverflow.com/questions/38639019/flink-kafka-consumer-groupid-not-working
From: TechnoMage [mailto:[hidden email]]
Sent: Wednesday, April 25, 2018 8:52 AM
To: Tzu-Li (Gordon) Tai
Cc: user
Subject: Re: Weird Kafka Connector issue
I have another java program reading the topic to monitor the test. It receives 60,000 records on the “travel” topic, while the kafka consumer only reports 4,138. That and the incongruity of the source to the maps are what seems very weird.
I have several other topics where the source is built with the exact same code, and where there are multiple maps following, and the numbers all match expectations.
Michael
On Apr 25, 2018, at 12:59 AM, Tzu-Li (Gordon) Tai <[hidden email]> wrote:
.
Just to clarify your observation here:
Is the problem the fact that map operators after the “source: travel” Kafka topic source do not receive all records from the source?
This does seem weird, but as of now I don’t really have ideas yet of how this could maybe be Flink related.
One other thing to be sure of - have you verified that the outputs of your test are incorrect?
Or are you assuming that it is incorrect based on the weird metric numbers shown on the web ui?
On 25 April 2018 at 6:13:07 AM, TechnoMage ([hidden email]) wrote:
Still trying to figure out what is happening with this kafka topic.
1) No exceptions in the task manager log or the UI exceptions tab.
2) Topic partitions being reset to offset 0 confirmed in log.
3) Other topics in this and other tests show full consumption of messages (all JSON format text).
4) The source shows more records output than are received by 2 of the 3 following stages.
The diagram for the job is below, as is the GUI showing tasks and record counts.
<[hidden email].>
I have been using the kafka connector sucessfully for a while now. But, am getting weird results in one case.
I have a test that submits 3 streams to kafka topics, and monitors them on a separate process. The flink job has a source for each topic, and one such is fed to 3 separate
map functions that lead to other operators. This topic only shows 6097 out of 30000 published, and the map functions following the source only show a fraction of that as received. The consumer is configured to start at the begining and in other cases the
same code receives all messages published. The parallelism is 6 if that makes a difference, as is the partitioning on the topics.
The code for creating the topic is below.
Any suggestions on why it is missing so many messages would be welcome.
String topic = a.kafkaTopicName(ets);
Properties props = new Properties();
props.setProperty("bootstrap.servers", servers);
props.setProperty("group.id", UUID.randomUUID().toString());
props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
DataStream<String> ds =
consumers.get(a.eventType);
FlinkKafkaConsumer011<String> cons = new FlinkKafkaConsumer011<String>(
topic, new SimpleStringSchema(), props);
cons.setStartFromEarliest();
ds = env.addSource(cons).name(et.name).rebalance();
consumers.put(a.eventType, ds);
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