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From "Josh Forman-Gornall (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-4190) Generalise RollingSink to work with arbitrary buckets
Date Mon, 11 Jul 2016 11:43:10 GMT
Josh Forman-Gornall created FLINK-4190:
------------------------------------------

             Summary: Generalise RollingSink to work with arbitrary buckets
                 Key: FLINK-4190
                 URL: https://issues.apache.org/jira/browse/FLINK-4190
             Project: Flink
          Issue Type: Improvement
          Components: filesystem-connector, Streaming Connectors
            Reporter: Josh Forman-Gornall
            Assignee: Josh Forman-Gornall
            Priority: Minor


The current RollingSink implementation appears to be intended for writing to directories that
are bucketed by system time (e.g. minutely) and to only be writing to one file within one
bucket at any point in time. When the system time determines that the current bucket should
be changed, the current bucket and file are closed and a new bucket and file are created.
The sink cannot be used for the more general problem of writing to arbitrary buckets, perhaps
determined by an attribute on the element/tuple being processed.

There are three limitations which prevent the existing sink from being used for more general
problems:
- Only bucketing by the current system time is supported, and not by e.g. an attribute of
the element being processed by the sink.
- Whenever the sink sees a change in the bucket being written to, it flushes the file and
moves on to the new bucket. Therefore the sink cannot have more than one bucket/file open
at a time. Additionally the checkpointing mechanics only support saving the state of one active
bucket and file.
- The sink determines that it should 'close' an active bucket and file when the bucket path
changes. We need another way to determine when a bucket has become inactive and needs to be
closed.



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