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From Narendra Kumar <NarendraKu...@fico.com>
Subject RE: Consumer with another group.id conflicts with streams()
Date Wed, 03 May 2017 11:10:35 GMT
Hi Matthias,

I enabled logs in the application and this is what I have observed -->

While rebalancing ProcessorNode.close() is getting  called twice, once from StreamThread.suspendTasksAndState()
and once from StreamThread.closeNonAssignedSuspendedTasks(). DebugTranDebugTransformer has
instance field of type KafkaConsumer to do some lookup. DebugTransformer.close() throws  exception
when called second time (i.e. IllegalStateException from  KafkaConsumer instance because it
is already closed.), we fail to close the task's state manager ( i.e. call to task.closeStateManager(true);
fails). StateManager is still holding lock to the task's state directory. After rebalance,
if the same task id is launched on same application instance but in different thread then
the task get stuck because it fails to get lock to the task's state directory. The task get
stuck forever and can't process any data from here. Depending on how much data was there on
the partition at the time of rebalance we see different number of alerts.

I have attached the log file for reference.

Thanks,
Narendra


-----Original Message-----
From: Andreas Voss
Sent: Tuesday, April 25, 2017 1:27 PM
To: users@kafka.apache.org
Cc: Narendra Kumar <NarendraKumar@fico.com>; Wladimir Schmidt <WladimirSchmidt@fico.com>;
Christian Leiner <ChristianLeiner@fico.com>
Subject: Re: Consumer with another group.id conflicts with streams()

Hi Matthias,

thank you for your response. Here are some more details:

- my input and output topics have 6 partitions each.
- my application instances run from docker images so the is no state left over from a previous
run
- I have a single docker container running kafka + zookeeper (spotify/kafka).
- when the second consumer is in place, I receive a random number of records in the target
topic (e.g. I send 1000 records and receive 439 on first run and 543 on second run)
- the problem only occurs if two instances of the application are running. If I only start
one instance then it's slow but when I send 1000 records I also receive 1000 records. I think
this is also an indicator for a bug, because a streaming app should behave the same, independent
of whether one or two instances are running.
- I added the properties you suggested, but behavior did not change.

I think this is a bug, consumers of different groups should not interact with each other.
Should I submit a bug report and if so, any suggestions on how to do that?

Andreas


-----Urspr√ľngliche Nachricht-----
Von: Matthias J. Sax [mailto:matthias@confluent.io]
Gesendet: Montag, 24. April 2017 19:18
An: users@kafka.apache.org
Betreff: Re: Consumer with another group.id conflicts with streams()

Hi,

hard to diagnose. The new consumer should not affect the Streams app though -- even if I am
wondering why you need it.

> KafkaConsumer (with a UUID as group.id) that reads some historical
> data from input topic

Maybe using GlobalKTable instead might be a better solution?

> (i.e. I feed 1000 records into source topic and receive around 200 on
> the target topic)

Are this the first 200 records? Or are those 200 record "random ones"
from your input topic? How many partitions do you have for input/output topic?

> looks like a lot of rebalancing happens.

We recommend to change StreamsConfig values as follows to improve in rebalance behavior:

> props.put(ProducerConfig.RETRIES_CONFIG, 10);  <---- increase to 10
> from default of 0
> props.put(ConsumerConfig.MAX_POLL_INTERVAL_MS_CONFIG,
> Integer.toString(Integer.MAX_VALUE)); <--------- increase to infinity
> from default of 300 s

We will change the default values accordingly in future release but for now you should set
this manually.


Hope this helps.


-Matthias

On 4/24/17 10:01 AM, Andreas Voss wrote:
> Hi, I have a simple streaming app that copies data from one topic to another, so when
I feed 1000 records into source topic I receive 1000 records in the target topic. Also the
app contains a transform() step which does nothing, except instantiating a KafkaConsumer (with
a UUID as group.id) that reads some historical data from input topic. As soon as this consumer
is in place, the streaming app does not work anymore, records get lost (i.e. I feed 1000 records
into source topic and receive around 200 on the target topic) and it's terribly slow - looks
like a lot of rebalancing happens.
>
> To me this looks like a bug, because the KStreamBuilder uses the application id as group.id
("kafka-smurfing" in this case), and the transformer uses a different one (uuid).
>
> Full source code:
>
> public class Main {
>
>   public static final String BOOTSTRAP_SERVERS = "192.168.99.100:9092";
>   public static final String SOURCE_TOPIC = "transactions";
>   public static final String TARGET_TOPIC =  "alerts";
>
>   public static void main(String[] args) throws Exception {
>
>     KStreamBuilder builder = new KStreamBuilder();
>     builder.stream(Serdes.String(), Serdes.String(), SOURCE_TOPIC)
>            .transform(() -> new DebugTransformer())
>            .to(Serdes.String(), Serdes.String(), TARGET_TOPIC);
>
>     Properties props = new Properties();
>     props.put(StreamsConfig.APPLICATION_ID_CONFIG, "kafka-smurfing");
>     props.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, Main.BOOTSTRAP_SERVERS);
>     props.put(StreamsConfig.KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
>     props.put(StreamsConfig.VALUE_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
>     props.put(StreamsConfig.NUM_STREAM_THREADS_CONFIG, 2);
>     props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
>
>     KafkaStreams streams = new KafkaStreams(builder, props);
>     streams.start();
>     Runtime.getRuntime().addShutdownHook(new Thread(streams::close));
>
>   }
>
> }
>
> public class DebugTransformer implements Transformer<String, String,
> KeyValue<String, String>> {
>
>   private KafkaConsumer<String, String> consumer;
>   private ProcessorContext context;
>
>   @Override
>   public void init(ProcessorContext context) {
>     this.context = context;
>     Properties props = new Properties();
>     props.put(ConsumerConfig.BOOTSTRAP_SERVERS_CONFIG, Main.BOOTSTRAP_SERVERS);
>     props.put(ConsumerConfig.GROUP_ID_CONFIG, UUID.randomUUID().toString());
>     props.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "none");
>     props.put(ConsumerConfig.ENABLE_AUTO_COMMIT_CONFIG, "false");
>     props.put(ConsumerConfig.KEY_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
>     props.put(ConsumerConfig.VALUE_DESERIALIZER_CLASS_CONFIG, StringDeserializer.class.getName());
>     consumer = new KafkaConsumer<>(props);
>   }
>
>   @Override
>   public KeyValue<String, String> transform(String key, String value) {
>     TopicPartition partition = new TopicPartition(Main.SOURCE_TOPIC, context.partition());
>     consumer.assign(Arrays.asList(partition));
>     consumer.seek(partition, 0);
>     consumer.poll(100);
>     return KeyValue.pair(key, value);
>   }
>
>   @Override
>   public void close() {
>     consumer.close();
>   }
>
>   @Override
>   public KeyValue<String, String> punctuate(long timestamp) {
>     return null;
>   }
>
> }
>
> Thanks for any hints,
> Andreas
>
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