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https://issues.apache.org/jira/browse/APEXMALHAR-2063?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15337430#comment-15337430
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ASF GitHub Bot commented on APEXMALHAR-2063:
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GitHub user chandnisingh opened a pull request:
https://github.com/apache/apex-malhar/pull/322
APEXMALHAR-2063 Made window data manager use file system wal
@PramodSSImmaneni @tweise @ilooner
Please review
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/chandnisingh/incubator-apex-malhar
APEXMALHAR-2063
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/apex-malhar/pull/322.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #322
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commit 11aaefe661b7a1149ab38bf14bf2fdc716ebb009
Author: Chandni Singh <csi...@apache.org>
Date: 2016-06-18T01:10:40Z
APEXMALHAR-2063 Made window data manager use file system wal
----
> Integrate WAL to FS WindowDataManager
> -------------------------------------
>
> Key: APEXMALHAR-2063
> URL: https://issues.apache.org/jira/browse/APEXMALHAR-2063
> Project: Apache Apex Malhar
> Issue Type: Improvement
> Reporter: Chandni Singh
> Assignee: Chandni Singh
>
> FS Window Data Manager is used to save meta-data that helps in replaying
> tuples every completed application window after failure. For this it saves
> meta-data in a file per window. Having multiple small size files on hdfs
> cause issues as highlighted here:
> http://blog.cloudera.com/blog/2009/02/the-small-files-problem/
> Instead FS Window Data Manager can utilize the WAL to write data and maintain
> a mapping of how much data was flushed to WAL each window.
> In order to use FileSystemWAL for replaying data of a finished window, there
> are few changes made to FileSystemWAL this is because of following:
> 1. WindowDataManager needs to reply data of every finished window. This
> window may not be checkpointed.
> FileSystemWAL truncates the WAL file to the checkpointed point after recovery
> so this poses a problem.
> WindowDataManager should be able to control recovery of FileSystemWAL.
> 2. FileSystemWAL writes to temporary files. The mapping of temp files to
> actual file is part of its state which is checkpointed. Since
> WindowDataManager replays data of a window not yet checkpointed, it needs to
> know the actual temporary file the data is being persisted to.
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