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From "Tim Robertson (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (BEAM-5036) Optimize FileBasedSink's WriteOperation.moveToOutput()
Date Tue, 28 Aug 2018 17:59:00 GMT

    [ https://issues.apache.org/jira/browse/BEAM-5036?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16595337#comment-16595337
] 

Tim Robertson edited comment on BEAM-5036 at 8/28/18 5:58 PM:
--------------------------------------------------------------

For info on the other rename() methods:
 * {{S3FileSystem}} implements {{rename()}} as a [copy and delete|https://github.com/apache/beam/blob/release-2.6.0/sdks/java/io/amazon-web-services/src/main/java/org/apache/beam/sdk/io/aws/s3/S3FileSystem.java#L597]
 * {{GcsFileSystem}} implements {{rename()}} as a [copy and delete|https://github.com/apache/beam/blob/release-2.6.0/sdks/java/extensions/google-cloud-platform-core/src/main/java/org/apache/beam/sdk/extensions/gcp/storage/GcsFileSystem.java#L122]
 * {{LocalFileSystem}} implements {{rename()}} by [making the parent directory if necessary|https://github.com/apache/beam/blob/release-2.6.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/LocalFileSystem.java#L164]
and then does a file move
 * {{HDFSFileSystem}} following BEAM-4861 (fixed and ready to merge) now implements {{rename()}} by
creating missing parent directories and doing the move

The move across different filesystems is not (fully) supported because the {{FileSystems.rename}}
gets only the [filesystem for the source resource|https://github.com/apache/beam/blob/release-2.6.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileSystems.java#L325].
It is not clear to me what might happen if the source were an {{HDFSFilesystem}} which itself
can span multiple Filesystems. It is also not currently clear to me where we can best do the
check - we could simply log a warn before the call to rename().


was (Author: timrobertson100):
For info on the other rename() methods:
 * {{S3FileSystem}} implements {{rename()}} as a [copy and delete|https://github.com/apache/beam/blob/release-2.6.0/sdks/java/io/amazon-web-services/src/main/java/org/apache/beam/sdk/io/aws/s3/S3FileSystem.java#L597]
 * {{GcsFileSystem}} implements {{rename()}} as a [copy and delete|https://github.com/apache/beam/blob/release-2.6.0/sdks/java/extensions/google-cloud-platform-core/src/main/java/org/apache/beam/sdk/extensions/gcp/storage/GcsFileSystem.java#L122]
 * {{LocalFileSystem}} implements {{rename()}} by [making the parent directory if necessary|https://github.com/apache/beam/blob/release-2.6.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/LocalFileSystem.java#L164]
and then does a file move
 * {{HDFSFileSystem}} following BEAM-4861 (fixed and ready to merge) now implements {{rename()}} by
creating missing parent directories and doing the move

The move across different filesystems is not (fully) supported because the {{FileSystems.rename}}
gets only the [filesystem for the source resource|https://github.com/apache/beam/blob/release-2.6.0/sdks/java/core/src/main/java/org/apache/beam/sdk/io/FileSystems.java#L325].
It is not clear to me what might happen if the source were an {{HDFSFilesystem}} which itself
can span multiple Filesystems. It is also not currently clear to me where we can best do the
check.

> Optimize FileBasedSink's WriteOperation.moveToOutput()
> ------------------------------------------------------
>
>                 Key: BEAM-5036
>                 URL: https://issues.apache.org/jira/browse/BEAM-5036
>             Project: Beam
>          Issue Type: Improvement
>          Components: io-java-files
>    Affects Versions: 2.5.0
>            Reporter: Jozef Vilcek
>            Assignee: Tim Robertson
>            Priority: Major
>
> moveToOutput() methods in FileBasedSink.WriteOperation implements move by copy+delete.
It would be better to use a rename() which can be much more effective for some filesystems.
> Filesystem must support cross-directory rename. BEAM-4861 is related to this for the
case of HDFS filesystem.
> Feature was discussed here:
> http://mail-archives.apache.org/mod_mbox/beam-dev/201807.mbox/%3CCAF9t7_4Mp54pQ+vRrJrBh9Vx0=uaKnuPZD_qdh_QDm9VXLLsZw@mail.gmail.com%3E



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