[SAMZA-342] Priority streams experience large latencies before being consumed by the stream processor

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.7.0
• Component/s: kafka

Environment

ubuntu 13.10

• Assignee: Unassigned
• Reporter: TJ Giuli
• Created: 16/Jul/14 22:36
• Updated: 30/Jul/14 00:34

Description

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.

Issue Links

• relates to: SAMZA-245 Improve SystemConsumers performance