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https://issues.apache.org/jira/browse/SAMZA-342?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14070618#comment-14070618
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Chris Riccomini commented on SAMZA-342:
---------------------------------------
Dang. If you're willing to keep debugging with me, let's try and figure this
out.
1. If you run the kafka-console-consumer script (found in the Kafka binary
release) pointed at the same Kafka cluster and topic:
{noformat}
bin/kafka-console-consumer.sh --zookeeper <host>:<port> --topic <your topic>
{noformat}
Do you see the message arrive to the console immediately while experiencing
delay in the TaskInstance?
2. It looks like you're running with TRACE in your SamzaContainer. The
KafkaSystemConsumer should log:
{code}
trace("Incoming message %s: %s." format (tp, msg))
{code}
Immediately after it polls the Kafka broker, and receives messages back. Do you
see those log messages? If so, how do their time stamps match up with the
others you posted earlier?
I'm trying to narrow down where the delay is being introduced.
> Priority streams experience large latencies before being consumed by the
> stream processor
> -----------------------------------------------------------------------------------------
>
> Key: SAMZA-342
> URL: https://issues.apache.org/jira/browse/SAMZA-342
> Project: Samza
> Issue Type: Bug
> Components: kafka
> Affects Versions: 0.7.0
> Environment: ubuntu 13.10
> Reporter: TJ Giuli
>
> I have a stream processor that takes inputs from multiple streams, some are
> more batch, non-latency sensitive and others are real-time, infrequently have
> traffic and should be low-latency. The real-time stream helps me interpret
> the batch stream, so I would ideally like any real-time stream envelopes
> delivered within some maximum latency from the time the message enters into a
> Kafka topic.
> I have my stream processor configured to prioritize my real-time streams over
> the batch streams, but I consistently find that the real-time stream is
> delayed by traffic from the batch stream. From tracing the Kafka consumer,
> it looks like my stream processor periodically fetches from Kafka, finds that
> the batch streams have a large chunk of messages waiting, doesn’t find
> anything on the real-time topics, and processes away the batch messages for a
> few minutes. During the batch processing, the Kafka consumer does not poll
> the real-time streams, so if a message is sent to a real-time topic, the
> message effectively doesn’t arrive until the next time the Kafka consumer
> does another fetch. When a real-time message is consumed by the Kafka
> consumer, the TieredPriorityChooser correctly prioritizes traffic from the
> real-time streams over the batch streams.
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