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https://issues.apache.org/jira/browse/SPARK-23977?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16609245#comment-16609245
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Wenchen Fan commented on SPARK-23977:
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I'm removing the target version, since we are not going to merge it to 2.4
> Add commit protocol binding to Hadoop 3.1 PathOutputCommitter mechanism
> -----------------------------------------------------------------------
>
> Key: SPARK-23977
> URL: https://issues.apache.org/jira/browse/SPARK-23977
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 2.4.0
> Reporter: Steve Loughran
> Priority: Minor
>
> Hadoop 3.1 adds a mechanism for job-specific and store-specific committers
> (MAPREDUCE-6823, MAPREDUCE-6956), and one key implementation, S3A committers,
> HADOOP-13786
> These committers deliver high-performance output of MR and spark jobs to S3,
> and offer the key semantics which Spark depends on: no visible output until
> job commit, a failure of a task at an stage, including partway through task
> commit, can be handled by executing and committing another task attempt.
> In contrast, the FileOutputFormat commit algorithms on S3 have issues:
> * Awful performance because files are copied by rename
> * FileOutputFormat v1: weak task commit failure recovery semantics as the
> (v1) expectation: "directory renames are atomic" doesn't hold.
> * S3 metadata eventual consistency can cause rename to miss files or fail
> entirely (SPARK-15849)
> Note also that FileOutputFormat "v2" commit algorithm doesn't offer any of
> the commit semantics w.r.t observability of or recovery from task commit
> failure, on any filesystem.
> The S3A committers address these by way of uploading all data to the
> destination through multipart uploads, uploads which are only completed in
> job commit.
> The new {{PathOutputCommitter}} factory mechanism allows applications to work
> with the S3A committers and any other, by adding a plugin mechanism into the
> MRv2 FileOutputFormat class, where it job config and filesystem configuration
> options can dynamically choose the output committer.
> Spark can use these with some binding classes to
> # Add a subclass of {{HadoopMapReduceCommitProtocol}} which uses the MRv2
> classes and {{PathOutputCommitterFactory}} to create the committers.
> # Add a {{BindingParquetOutputCommitter extends ParquetOutputCommitter}}
> to wire up Parquet output even when code requires the committer to be a
> subclass of {{ParquetOutputCommitter}}
> This patch builds on SPARK-23807 for setting up the dependencies.
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