[jira] [Created] (KAFKA-1417) Very slow initial high-level consumer startup in low traffic/blocking fetch scenario

["Sam Meder (JIRA)" <ji...@apache.org>]

Sam Meder created KAFKA-1417:
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             Summary: Very slow initial high-level consumer startup in low traffic/blocking fetch scenario
                 Key: KAFKA-1417
                 URL: https://issues.apache.org/jira/browse/KAFKA-1417
             Project: Kafka
          Issue Type: Bug
          Components: consumer
    Affects Versions: 0.8.0
            Reporter: Sam Meder
            Assignee: Neha Narkhede


We're seeing very slow startup times when starting a high level consumer in a low traffic/blocking fetch type setup. The example we've come across has a consumer that is set up to use 3 topics and uses a 20s/1 byte fetch timeout. What happens is that the leader finder thread adds partitions one by one and since the offset is not know this causes a call to figure out the offset. This call uses the fetcher threads simple consumer instance and locks around the call. Initially this is not a problem, but as soon as the fetcher thread has some partitions it will start fetching and since this is a low traffic situation the fetch will at least sometimes take up to 20s (again locking around the simple consumer). This leads to behavior like:

# Finder thread adds a partition
# Data thread notices it has partitions to fetch data for, locks the consumer for 20s
# Finder thread tries to add a partition, tries to lock consumer and blocks for 20s
# Rinse, repeat for each partition



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