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https://issues.apache.org/jira/browse/FLINK-5789?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16212540#comment-16212540
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Piotr Nowojski edited comment on FLINK-5789 at 10/20/17 12:20 PM:
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After short discussion with [~aljoscha] about
https://issues.apache.org/jira/browse/FLINK-7737, we kind of agreed that
current {{FSDataOutputStream}} interface is not sufficient/kind of weird if we
want it to be used in BucketingSink.
The issue is that depending on underlying FileSystem to "persist" snapshots we
sometimes want to call {{hflush()}} (for regular HDFS) and sometimes
{{hsync()}} (in S3 like environments). As [~StephanEwen] proposed it probably
would be best to let {{FileSystem}} decide which one should be called to
"persist" the data. But in that case the methods in {{FSDataOutputStream}}
"flush" and "sync" are kind of strange and misleading. Maybe we should add a
new one {{FSDataOutputStream::persist()}} (with default implementation calling
{{sync()}}), which should be used by BucketingSink (and state backends?). At
the same time I do not see a valid usage for {{FSDataOutputStream::flush()}},
so maybe we should drop/deprecate it?
was (Author: pnowojski):
After short discussion with [~aljoscha] about
https://issues.apache.org/jira/browse/FLINK-7737, we kind of agreed that
current {{FSDataOutputStream}} interface is not sufficient/kind of weird if we
want it to be used in BucketingSink.
The issue is that depending on underlying FileSystem to "persist" snapshots we
sometimes want to call {{hflush()}} (for regular HDFS) and sometimes
{{hsync()}} (in S3 like environments). As [~StephanEwen] proposed it probably
would best let {{FileSystem}} decide which one should be called to "persist"
the data. But in that case calling the methods in {{FSDataOutputStream}}
"flush" and "sync" is kind of strange and misleading. Maybe we should add a new
one {{FSDataOutputStream::persist()}} (with default implementation calling
{{sync()}}, which should be called by BucketingSink (and state backends?) and
the concrete implementation of the {{FileSystem}} could decided how to
interpret the {{FSDataOutputStream::persist()}} calls. At the same time I do
not see a valid usage for {{FSDataOutputStream::flush()}}, so maybe we should
drop/deprecate it?
> Make Bucketing Sink independent of Hadoop's FileSystem
> ------------------------------------------------------
>
> Key: FLINK-5789
> URL: https://issues.apache.org/jira/browse/FLINK-5789
> Project: Flink
> Issue Type: Bug
> Components: Streaming Connectors
> Affects Versions: 1.2.0, 1.1.4
> Reporter: Stephan Ewen
> Assignee: Gary Yao
> Fix For: 1.4.0
>
>
> The {{BucketingSink}} is hard wired to Hadoop's FileSystem, bypassing Flink's
> file system abstraction.
> This causes several issues:
> - The bucketing sink will behave different than other file sinks with
> respect to configuration
> - Directly supported file systems (not through hadoop) like the MapR File
> System does not work in the same way with the BuketingSink as other file
> systems
> - The previous point is all the more problematic in the effort to make
> Hadoop an optional dependency and with in other stacks (Mesos, Kubernetes,
> AWS, GCE, Azure) with ideally no Hadoop dependency.
> We should port the {{BucketingSink}} to use Flink's FileSystem classes.
> To support the *truncate* functionality that is needed for the exactly-once
> semantics of the Bucketing Sink, we should extend Flink's FileSystem
> abstraction to have the methods
> - {{boolean supportsTruncate()}}
> - {{void truncate(Path, long)}}
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