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From "Ewan Higgs (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-13186) [WRITE] Multipart Multinode uploader API + Implementations
Date Fri, 09 Mar 2018 09:59:00 GMT

     [ https://issues.apache.org/jira/browse/HDFS-13186?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ewan Higgs updated HDFS-13186:
------------------------------
    Attachment:     (was: HDFS-13186.002.patch)

> [WRITE] Multipart Multinode uploader API + Implementations
> ----------------------------------------------------------
>
>                 Key: HDFS-13186
>                 URL: https://issues.apache.org/jira/browse/HDFS-13186
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Ewan Higgs
>            Priority: Major
>         Attachments: HDFS-13186.patch
>
>
> To write files in parallel to an external storage system as in HDFS-12090, there are
two approaches:
>  # Naive approach: use a single datanode per file that copies blocks locally as it streams
data to the external service. This requires a copy for each block inside the HDFS system and
then a copy for the block to be sent to the external system.
>  # Better approach: Single point (e.g. Namenode or SPS style external client) and Datanodes
coordinate in a multipart - multinode upload.
> This system needs to work with multiple back ends and needs to coordinate across the
network. So we propose an API that resembles the following:
> {code:java}
> public UploadHandle multipartInit(Path filePath) throws IOException;
> public PartHandle multipartPutPart(InputStream inputStream,
>     int partNumber, UploadHandle uploadId) throws IOException;
> public void multipartComplete(Path filePath,
>     List<Pair<Integer, PartHandle>> handles, 
>     UploadHandle multipartUploadId) throws IOException;{code}
> Here, UploadHandle and PartHandle are opaque handlers in the vein of PathHandle so they
can be serialized and deserialized in hadoop-hdfs project without knowledge of how to deserialize
e.g. S3A's version of a UpoadHandle and PartHandle.
> In an object store such as S3A, the implementation is straight forward. In the case of
writing multipart/multinode to HDFS, we can write each block as a file part. The complete
call will perform a concat on the blocks.



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