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https://issues.apache.org/jira/browse/HADOOP-15320?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16416424#comment-16416424
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Chris Douglas commented on HADOOP-15320:
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Thanks [~shanyu]. Running this through Jenkins.
We could add a unit test to signal that a change to the default behavior could
affect these FS implementations, but that should be implied.
> Remove customized getFileBlockLocations for hadoop-azure and
> hadoop-azure-datalake
> ----------------------------------------------------------------------------------
>
> Key: HADOOP-15320
> URL: https://issues.apache.org/jira/browse/HADOOP-15320
> Project: Hadoop Common
> Issue Type: Bug
> Components: fs/adl, fs/azure
> Affects Versions: 2.7.3, 2.9.0, 3.0.0
> Reporter: shanyu zhao
> Assignee: shanyu zhao
> Priority: Major
> Attachments: HADOOP-15320.patch
>
>
> hadoop-azure and hadoop-azure-datalake have its own implementation of
> getFileBlockLocations(), which faked a list of artificial blocks based on the
> hard-coded block size. And each block has one host with name "localhost".
> Take a look at this code:
> [https://github.com/apache/hadoop/blob/release-2.9.0-RC3/hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azure/NativeAzureFileSystem.java#L3485]
> This is a unnecessary mock up for a "remote" file system to mimic HDFS. And
> the problem with this mock is that for large (~TB) files we generates lots of
> artificial blocks, and FileInputFormat.getSplits() is slow in calculating
> splits based on these blocks.
> We can safely remove this customized getFileBlockLocations() implementation,
> fall back to the default FileSystem.getFileBlockLocations() implementation,
> which is to return 1 block for any file with 1 host "localhost". Note that
> this doesn't mean we will create much less splits, because the number of
> splits is still limited by the blockSize in
> FileInputFormat.computeSplitSize():
> {code:java}
> return Math.max(minSize, Math.min(goalSize, blockSize));{code}
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