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From Ivan von Nagy <i...@vadio.com>
Subject Re: Instability issues with Spark 2.0.1 and Kafka 0.10
Date Thu, 10 Nov 2016 16:26:19 GMT
Ok, I have split he KafkaRDD logic to each use their own group and bumped
the poll.ms to 10 seconds. Anything less then 2 seconds on the poll.ms ends
up with a timeout and exception so I am still perplexed on that one. The
new error I am getting now is a `ConcurrentModificationException` when
Spark is trying to remove the CachedKafkaConsumer.

java.util.ConcurrentModificationException: KafkaConsumer is not safe for
multi-threaded access
at
org.apache.kafka.clients.consumer.KafkaConsumer.acquire(KafkaConsumer.java:1431)
at
org.apache.kafka.clients.consumer.KafkaConsumer.close(KafkaConsumer.java:1361)
at
org.apache.spark.streaming.kafka010.CachedKafkaConsumer$$anon$1.removeEldestEntry(CachedKafkaConsumer.scala:128)
at java.util.LinkedHashMap.afterNodeInsertion(LinkedHashMap.java:299)

Here is the basic logic:

*Using KafkaRDD* - This takes a list of channels and processes them in
parallel using the KafkaRDD directly. They each use a distinct consumer
group (s"$prefix-$topic"), and each has it's own topic and each topic has 4
partitions. We routinely get timeout errors when polling for data when the
poll.ms is less then 2 seconds. This occurs whether we process in parallel.

*Example usage with KafkaRDD:*
val channels = Seq("channel1", "channel2")

channels.toParArray.foreach { channel =>
  val consumer = new KafkaConsumer[K, V](kafkaParams.asJava)

  // Get offsets for the given topic and the consumer group "$prefix-$topic"

  val offsetRanges = getOffsets(s"$prefix-$topic", channel)

  val ds = KafkaUtils.createRDD[K, V](context,
        kafkaParams asJava,
        offsetRanges,
        PreferConsistent).toDS[V]

  // Do some aggregations
  ds.agg(...)
  // Save the data
  ds.write.mode(SaveMode.Append).parquet(somePath)
  // Save offsets using a KafkaConsumer
  consumer.commitSync(newOffsets.asJava)
  consumer.close()
}

I am not sure why the concurrent issue is there as I have tried to debug
and also looked at the KafkaConsumer code as well, but everything looks
like it should not occur. The things to figure out is why when running in
parallel does this occur and also why the timeouts still occur.

Thanks,

Ivan

On Mon, Nov 7, 2016 at 11:55 AM, Cody Koeninger <cody@koeninger.org> wrote:

> There definitely is Kafka documentation indicating that you should use
> a different consumer group for logically different subscribers, this
> is really basic to Kafka:
>
> http://kafka.apache.org/documentation#intro_consumers
>
> As for your comment that "commit async after each RDD, which is not
> really viable also", how is it not viable?  Again, committing offsets
> to Kafka doesn't give you reliable delivery semantics unless your
> downstream data store is idempotent.  If your downstream data store is
> idempotent, then it shouldn't matter to you when offset commits
> happen, as long as they happen within a reasonable time after the data
> is written.
>
> Do you want to keep arguing with me, or follow my advice and proceed
> with debugging any remaining issues after you make the changes I
> suggested?
>
> On Mon, Nov 7, 2016 at 1:35 PM, Ivan von Nagy <ivan@vadio.com> wrote:
> > With our stream version, we update the offsets for only the partition we
> > operating on. We even break down the partition into smaller batches and
> then
> > update the offsets after each batch within the partition. With Spark 1.6
> and
> > Kafka 0.8.x this was not an issue, and as Sean pointed out, this is not
> > necessarily a Spark issue since Kafka no longer allows you to simply
> update
> > the offsets for a given consumer group. You have to subscribe or assign
> > partitions to even do so.
> >
> > As for storing the offsets in some other place like a DB, it don't find
> this
> > useful because you then can't use tools like Kafka Manager. In order to
> do
> > so you would have to store in a DB and the circle back and update Kafka
> > afterwards. This means you have to keep two sources in sync which is not
> > really a good idea.
> >
> > It is a challenge in Spark to use the Kafka offsets since the drive keeps
> > subscribed to the topic(s) and consumer group, while the executors
> prepend
> > "spark-executor-" to the consumer group. The stream (driver) does allow
> you
> > to commit async after each RDD, which is not really viable also. I have
> not
> > of implementing an Akka actor system on the driver and send it messages
> from
> > the executor code to update the offsets, but then that is asynchronous as
> > well so not really a good solution.
> >
> > I have no idea why Kafka made this change and also why in the parallel
> > KafkaRDD application we would be advised to use different consumer groups
> > for each RDD. That seems strange to me that different consumer groups
> would
> > be required or advised. There is no Kafka documentation that I know if
> that
> > states this. The biggest issue I see with the parallel KafkaRDD is the
> > timeouts. I have tried to set poll.ms to 30 seconds and still get the
> issue.
> > Something is not right here and just not seem right. As I mentioned with
> the
> > streaming application, with Spark 1.6 and Kafka 0.8.x we never saw this
> > issue. We have been running the same basic logic for over a year now
> without
> > one hitch at all.
> >
> > Ivan
> >
> >
> > On Mon, Nov 7, 2016 at 11:16 AM, Cody Koeninger <cody@koeninger.org>
> wrote:
> >>
> >> Someone can correct me, but I'm pretty sure Spark dstreams (in
> >> general, not just kafka) have been progressing on to the next batch
> >> after a given batch aborts for quite some time now.  Yet another
> >> reason I put offsets in my database transactionally.  My jobs throw
> >> exceptions if the offset in the DB isn't what I expected it to be.
> >>
> >>
> >>
> >>
> >> On Mon, Nov 7, 2016 at 1:08 PM, Sean McKibben <graphex@graphex.com>
> wrote:
> >> > I've been encountering the same kinds of timeout issues as Ivan, using
> >> > the "Kafka Stream" approach that he is using, except I'm storing my
> offsets
> >> > manually from the driver to Zookeeper in the Kafka 8 format. I
> haven't yet
> >> > implemented the KafkaRDD approach, and therefore don't have the
> concurrency
> >> > issues, but a very similar use case is coming up for me soon, it's
> just been
> >> > backburnered until I can get streaming to be more reliable (I will
> >> > definitely ensure unique group IDs when I do). Offset commits are
> certainly
> >> > more painful in Kafka 0.10, and that doesn't have anything to do with
> Spark.
> >> >
> >> > While i may be able to alleviate the timeout by just increasing it,
> I've
> >> > noticed something else that is more worrying: When one task fails 4
> times in
> >> > a row (i.e. "Failed to get records for _ after polling for _"), Spark
> aborts
> >> > the Stage and Job with "Job aborted due to stage failure: Task _ in
> stage _
> >> > failed 4 times". That's fine, and it's the behavior I want, but
> instead of
> >> > stopping the Application there (as previous versions of Spark did)
> the next
> >> > microbatch marches on and offsets are committed ahead of the failed
> >> > microbatch. Suddenly my at-least-once app becomes more
> >> > sometimes-at-least-once which is no good. In order for spark to
> display that
> >> > failure, I must be propagating the errors up to Spark, but the
> behavior of
> >> > marching forward with the next microbatch seems to be new, and a big
> >> > potential for data loss in streaming applications.
> >> >
> >> > Am I perhaps missing a setting to stop the entire streaming
> application
> >> > once spark.task.maxFailures is reached? Has anyone else seen this
> behavior
> >> > of a streaming application skipping over failed microbatches?
> >> >
> >> > Thanks,
> >> > Sean
> >> >
> >> >
> >> >> On Nov 4, 2016, at 2:48 PM, Cody Koeninger <cody@koeninger.org>
> wrote:
> >> >>
> >> >> So basically what I am saying is
> >> >>
> >> >> - increase poll.ms
> >> >> - use a separate group id everywhere
> >> >> - stop committing offsets under the covers
> >> >>
> >> >> That should eliminate all of those as possible causes, and then we
> can
> >> >> see if there are still issues.
> >> >>
> >> >> As far as 0.8 vs 0.10, Spark doesn't require you to assign or
> >> >> subscribe to a topic in order to update offsets, Kafka does.  If you
> >> >> don't like the new Kafka consumer api, the existing 0.8 simple
> >> >> consumer api should be usable with later brokers.  As long as you
> >> >> don't need SSL or dynamic subscriptions, and it meets your needs,
> keep
> >> >> using it.
> >> >>
> >> >> On Fri, Nov 4, 2016 at 3:37 PM, Ivan von Nagy <ivan@vadio.com>
> wrote:
> >> >>> Yes, the parallel KafkaRDD uses the same consumer group, but each
> RDD
> >> >>> uses a
> >> >>> single distinct topic. For example, the group would be something
> like
> >> >>> "storage-group", and the topics would be "storage-channel1", and
> >> >>> "storage-channel2". In each thread a KafkaConsumer is started,
> >> >>> assigned the
> >> >>> partitions assigned, and then commit offsets are called after the
> RDD
> >> >>> is
> >> >>> processed. This should not interfere with the consumer group used
by
> >> >>> the
> >> >>> executors which would be "spark-executor-storage-group".
> >> >>>
> >> >>> In the streaming example there is a single topic ("client-events")
> and
> >> >>> group
> >> >>> ("processing-group"). A single stream is created and offsets are
> >> >>> manually
> >> >>> updated from the executor after each partition is handled. This
was
> a
> >> >>> challenge since Spark now requires one to assign or subscribe to
a
> >> >>> topic in
> >> >>> order to even update the offsets. In 0.8.2.x you did not have to
> worry
> >> >>> about
> >> >>> that. This approach limits your exposure to duplicate data since
> >> >>> idempotent
> >> >>> records are not entirely possible in our scenario. At least without
> a
> >> >>> lot of
> >> >>> re-running of logic to de-dup.
> >> >>>
> >> >>> Thanks,
> >> >>>
> >> >>> Ivan
> >> >>>
> >> >>> On Fri, Nov 4, 2016 at 1:24 PM, Cody Koeninger <cody@koeninger.org>
> >> >>> wrote:
> >> >>>>
> >> >>>> So just to be clear, the answers to my questions are
> >> >>>>
> >> >>>> - you are not using different group ids, you're using the same
> group
> >> >>>> id everywhere
> >> >>>>
> >> >>>> - you are committing offsets manually
> >> >>>>
> >> >>>> Right?
> >> >>>>
> >> >>>> If you want to eliminate network or kafka misbehavior as a
source,
> >> >>>> tune poll.ms upwards even higher.
> >> >>>>
> >> >>>> You must use different group ids for different rdds or streams.
> >> >>>> Kafka consumers won't behave the way you expect if they are
all in
> >> >>>> the
> >> >>>> same group id, and the consumer cache is keyed by group id.
Yes,
> the
> >> >>>> executor will tack "spark-executor-" on to the beginning, but
if
> you
> >> >>>> give it the same base group id, it will be the same.  And the
> driver
> >> >>>> will use the group id you gave it, unmodified.
> >> >>>>
> >> >>>> Finally, I really can't help you if you're manually writing
your
> own
> >> >>>> code to commit offsets directly to Kafka.  Trying to minimize
> >> >>>> duplicates that way doesn't really make sense, your system
must be
> >> >>>> able to handle duplicates if you're using kafka as an offsets
> store,
> >> >>>> it can't do transactional exactly once.
> >> >>>>
> >> >>>> On Fri, Nov 4, 2016 at 1:48 PM, vonnagy <ivan@vadio.com>
wrote:
> >> >>>>> Here are some examples and details of the scenarios. The
KafkaRDD
> is
> >> >>>>> the
> >> >>>>> most
> >> >>>>> error prone to polling
> >> >>>>> timeouts and concurrentm modification errors.
> >> >>>>>
> >> >>>>> *Using KafkaRDD* - This takes a list of channels and processes
> them
> >> >>>>> in
> >> >>>>> parallel using the KafkaRDD directly. they all use the
same
> consumer
> >> >>>>> group
> >> >>>>> ('storage-group'), but each has it's own topic and each
topic has
> 4
> >> >>>>> partitions. We routinely get timeout errors when polling
for data.
> >> >>>>> This
> >> >>>>> occurs whether we process in parallel or sequentially.
> >> >>>>>
> >> >>>>> *Spark Kafka setting:*
> >> >>>>> spark.streaming.kafka.consumer.poll.ms=2000
> >> >>>>>
> >> >>>>> *Kafka Consumer Params:*
> >> >>>>> metric.reporters = []
> >> >>>>> metadata.max.age.ms = 300000
> >> >>>>> partition.assignment.strategy =
> >> >>>>> [org.apache.kafka.clients.consumer.RangeAssignor]
> >> >>>>> reconnect.backoff.ms = 50
> >> >>>>> sasl.kerberos.ticket.renew.window.factor = 0.8
> >> >>>>> max.partition.fetch.bytes = 1048576
> >> >>>>> bootstrap.servers = [somemachine:31000]
> >> >>>>> ssl.keystore.type = JKS
> >> >>>>> enable.auto.commit = false
> >> >>>>> sasl.mechanism = GSSAPI
> >> >>>>> interceptor.classes = null
> >> >>>>> exclude.internal.topics = true
> >> >>>>> ssl.truststore.password = null
> >> >>>>> client.id =
> >> >>>>> ssl.endpoint.identification.algorithm = null
> >> >>>>> max.poll.records = 1000
> >> >>>>> check.crcs = true
> >> >>>>> request.timeout.ms = 40000
> >> >>>>> heartbeat.interval.ms = 3000
> >> >>>>> auto.commit.interval.ms = 5000
> >> >>>>> receive.buffer.bytes = 65536
> >> >>>>> ssl.truststore.type = JKS
> >> >>>>> ssl.truststore.location = null
> >> >>>>> ssl.keystore.password = null
> >> >>>>> fetch.min.bytes = 1
> >> >>>>> send.buffer.bytes = 131072
> >> >>>>> value.deserializer = class
> >> >>>>> com.vadio.analytics.spark.storage.ClientEventJsonOptionDeseriali
> zer
> >> >>>>> group.id = storage-group
> >> >>>>> retry.backoff.ms = 100
> >> >>>>> sasl.kerberos.kinit.cmd = /usr/bin/kinit
> >> >>>>> sasl.kerberos.service.name = null
> >> >>>>> sasl.kerberos.ticket.renew.jitter = 0.05
> >> >>>>> ssl.trustmanager.algorithm = PKIX
> >> >>>>> ssl.key.password = null
> >> >>>>> fetch.max.wait.ms = 500
> >> >>>>> sasl.kerberos.min.time.before.relogin = 60000
> >> >>>>> connections.max.idle.ms = 540000
> >> >>>>> session.timeout.ms = 30000
> >> >>>>> metrics.num.samples = 2
> >> >>>>> key.deserializer = class
> >> >>>>> org.apache.kafka.common.serialization.StringDeserializer
> >> >>>>> ssl.protocol = TLS
> >> >>>>> ssl.provider = null
> >> >>>>> ssl.enabled.protocols = [TLSv1.2, TLSv1.1, TLSv1]
> >> >>>>> ssl.keystore.location = null
> >> >>>>> ssl.cipher.suites = null
> >> >>>>> security.protocol = PLAINTEXT
> >> >>>>> ssl.keymanager.algorithm = SunX509
> >> >>>>> metrics.sample.window.ms = 30000
> >> >>>>> auto.offset.reset = earliest
> >> >>>>>
> >> >>>>> *Example usage with KafkaRDD:*
> >> >>>>> val channels = Seq("channel1", "channel2")
> >> >>>>>
> >> >>>>> channels.toParArray.foreach { channel =>
> >> >>>>>  val consumer = new KafkaConsumer[K, V](kafkaParams.asJava)
> >> >>>>>
> >> >>>>>  // Get offsets for the given topic and the consumer group
> >> >>>>> 'storage-group'
> >> >>>>>  val offsetRanges = getOffsets("storage-group", channel)
> >> >>>>>
> >> >>>>>  val ds = KafkaUtils.createRDD[K, V](context,
> >> >>>>>        kafkaParams asJava,
> >> >>>>>        offsetRanges,
> >> >>>>>        PreferConsistent).toDS[V]
> >> >>>>>
> >> >>>>>  // Do some aggregations
> >> >>>>>  ds.agg(...)
> >> >>>>>  // Save the data
> >> >>>>>  ds.write.mode(SaveMode.Append).parquet(somePath)
> >> >>>>>  // Save offsets using a KafkaConsumer
> >> >>>>>  consumer.commitSync(newOffsets.asJava)
> >> >>>>>  consumer.close()
> >> >>>>> }
> >> >>>>>
> >> >>>>>
> >> >>>>> *Example usage with Kafka Stream:*
> >> >>>>> This creates a stream and processes events in each partition.
At
> the
> >> >>>>> end
> >> >>>>> of
> >> >>>>> processing for
> >> >>>>> each partition, we updated the offsets for each partition.
This is
> >> >>>>> challenging to do, but is better
> >> >>>>> then calling commitAysnc on the stream, because that occurs
after
> >> >>>>> the
> >> >>>>> /entire/ RDD has been
> >> >>>>> processed. This method minimizes duplicates in an exactly
once
> >> >>>>> environment.
> >> >>>>> Since the executors
> >> >>>>> use their own custom group "spark-executor-processor-group"
and
> the
> >> >>>>> commit
> >> >>>>> is buried in private
> >> >>>>> functions we are unable to use the executors cached consumer
to
> >> >>>>> update
> >> >>>>> the
> >> >>>>> offsets. This requires us
> >> >>>>> to go through multiple steps to update the Kafka offsets
> >> >>>>> accordingly.
> >> >>>>>
> >> >>>>> val offsetRanges = getOffsets("processor-group", "my-topic")
> >> >>>>>
> >> >>>>> val stream = KafkaUtils.createDirectStream[K, V](context,
> >> >>>>>      PreferConsistent,
> >> >>>>>      Subscribe[K, V](Seq("my-topic") asJavaCollection,
> >> >>>>>        kafkaParams,
> >> >>>>>        offsetRanges))
> >> >>>>>
> >> >>>>> stream.foreachRDD { rdd =>
> >> >>>>>    val offsetRanges = rdd.asInstanceOf[
> HasOffsetRanges].offsetRanges
> >> >>>>>
> >> >>>>>    // Transform our data
> >> >>>>>   rdd.foreachPartition { events =>
> >> >>>>>       // Establish a consumer in the executor so we can
update
> >> >>>>> offsets
> >> >>>>> after each partition.
> >> >>>>>       // This class is homegrown and uses the KafkaConsumer
to
> help
> >> >>>>> get/set
> >> >>>>> offsets
> >> >>>>>       val consumer = new ConsumerUtils(kafkaParams)
> >> >>>>>       // do something with our data
> >> >>>>>
> >> >>>>>       // Write the offsets that were updated in this partition
> >> >>>>>       kafkaConsumer.setConsumerOffsets("processor-group",
> >> >>>>>          Map(TopicAndPartition(tp.topic, tp.partition)
->
> >> >>>>> endOffset))
> >> >>>>>   }
> >> >>>>> }
> >> >>>>>
> >> >>>>>
> >> >>>>>
> >> >>>>> --
> >> >>>>> View this message in context:
> >> >>>>>
> >> >>>>> http://apache-spark-user-list.1001560.n3.nabble.com/
> Instability-issues-with-Spark-2-0-1-and-Kafka-0-10-tp28017p28020.html
> >> >>>>> Sent from the Apache Spark User List mailing list archive
at
> >> >>>>> Nabble.com.
> >> >>>>>
> >> >>>>>
> >> >>>>> ------------------------------------------------------------
> ---------
> >> >>>>> To unsubscribe e-mail: user-unsubscribe@spark.apache.org
> >> >>>>>
> >> >>>
> >> >>>
> >> >>
> >> >> ------------------------------------------------------------
> ---------
> >> >> To unsubscribe e-mail: user-unsubscribe@spark.apache.org
> >> >>
> >> >
> >
> >
>

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