Hi again,

One more observation: The problem only occurs when the two application 
instances are started one after the other with some delay in-between (7 seconds 
in my test setup). So the first instance already started to process the events 
that were in the queue, when the second instance came up. Looks like the second 
instance tries to initiate a rebalance that fails.

Thanks,
Andreas


-----Ursprüngliche Nachricht-----
Von: Narendra Kumar
Gesendet: Mittwoch, 3. Mai 2017 13:11
An: Andreas Voss <andreasv...@fico.com>; users@kafka.apache.org
Cc: Wladimir Schmidt <wladimirschm...@fico.com>; Christian Leiner 
<christianlei...@fico.com>
Betreff: RE: Consumer with another group.id conflicts with streams()

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 <narendraku...@fico.com>; Wladimir Schmidt 
<wladimirschm...@fico.com>; Christian Leiner <christianlei...@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


-----Ursprüngliche Nachricht-----
Von: Matthias J. Sax [mailto:matth...@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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