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From "Tzu-Li (Gordon) Tai (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-7407) Assumption of partition id strict contiguity is too naive in Kafka consumer's AbstractPartitionDiscoverer
Date Thu, 10 Aug 2017 05:16:03 GMT
Tzu-Li (Gordon) Tai created FLINK-7407:
------------------------------------------

             Summary: Assumption of partition id strict contiguity is too naive in Kafka consumer's
AbstractPartitionDiscoverer
                 Key: FLINK-7407
                 URL: https://issues.apache.org/jira/browse/FLINK-7407
             Project: Flink
          Issue Type: Improvement
          Components: Kafka Connector
            Reporter: Tzu-Li (Gordon) Tai
             Fix For: 1.4.0


In the Kafka Consumer's {{AbstractPartitionDiscoverer}}, for partition discovery, already
discovered partitions are tracked with the following map:
```
Map<String, Integer> topicsToLargestDiscoveredPartitionId
```

Simply put, on each discovery attempt's metadata fetch, all partition ids of a given topic
that are smaller than the largest seen id will be ignored and not assigned. This approach
lies on the assumption that fetched partition ids of a single topic are always strictly contiguous
starting from 0.

This assumption may be too naive, in that partitions which were temporarily unavailable at
the time of a discovery would be shadowed by available partitions with larger ids, and from
then on would be left unassigned.

We should redesign how the `AbstractPartitionDiscoverer` tracks discovered partitions by not
relying on the contiguity assumption, and also add test cases for non-contiguous fetched partition
ids.



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