[jira] [Updated] (HADOOP-13282) S3 blob etags to be made visible in S3A status/getFileChecksum() calls

["Steve Loughran (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HADOOP-13282?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Steve Loughran updated HADOOP-13282:
------------------------------------
    Hadoop Flags: Incompatible change
    Release Note: 
now that S3A has a checksum, you need to explicitly disable checksums when uploading from HDFS : use -skipCrc

checksum verification does work between s3a buckets, provided the block size on uploads was identical

> S3 blob etags to be made visible in S3A status/getFileChecksum() calls
> ----------------------------------------------------------------------
>
>                 Key: HADOOP-13282
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13282
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>    Affects Versions: 2.9.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>            Priority: Minor
>             Fix For: 3.1.0
>
>         Attachments: HADOOP-13282-001.patch, HADOOP-13282-002.patch, HADOOP-13282-003.patch, HADOOP-13282-004.patch
>
>
> If the etags of blobs were exported via {{getFileChecksum()}}, it'd be possible to probe for a blob being in sync with a local file. Distcp could use this to decide whether to skip a file or not.
> Now, there's a problem there: distcp needs source and dest filesystems to implement the same algorithm. It'd only work out the box if you were copying between S3 instances. There are also quirks with encryption and multipart: [s3 docs|http://docs.aws.amazon.com/AmazonS3/latest/API/RESTCommonResponseHeaders.html]. At the very least, it's something which could be used when indexing the FS, to check for changes later.



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