[jira] [Resolved] (HADOOP-16279) S3Guard: Implement time-based (TTL) expiry for entries (and tombstones)

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

     [ https://issues.apache.org/jira/browse/HADOOP-16279?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Steve Loughran resolved HADOOP-16279.
-------------------------------------
       Resolution: Fixed
    Fix Version/s: 3.3.0

+1

committed to trunk. Thanks!

> S3Guard: Implement time-based (TTL) expiry for entries (and tombstones)
> -----------------------------------------------------------------------
>
>                 Key: HADOOP-16279
>                 URL: https://issues.apache.org/jira/browse/HADOOP-16279
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>            Reporter: Gabor Bota
>            Assignee: Gabor Bota
>            Priority: Major
>             Fix For: 3.3.0
>
>         Attachments: Screenshot 2019-05-17 at 13.21.26.png
>
>
> In HADOOP-15621 we implemented TTL for Authoritative Directory Listings and added {{ExpirableMetadata}}. {{DDBPathMetadata}} extends {{PathMetadata}} extends {{ExpirableMetadata}}, so all metadata entries in ddb can expire, but the implementation is not done yet. 
> To complete this feature the following should be done:
> * Add new tests for metadata entry and tombstone expiry to {{ITestS3GuardTtl}}
> * Implement metadata entry and tombstone expiry 
> I would like to start a debate on whether we need to use separate expiry times for entries and tombstones. My +1 on not using separate settings - so only one config name and value.
> ----
> Notes:
> * In HADOOP-13649 the metadata TTL is implemented in LocalMetadataStore, using an existing feature in guava's cache implementation. Expiry is set with {{fs.s3a.s3guard.local.ttl}}.
> * LocalMetadataStore's TTL and this TTL is different. That TTL is using the guava cache's internal solution for the TTL of these entries. This is an S3AFileSystem level solution in S3Guard, a layer above all metadata store.
> * This is not the same, and not using the [DDB's TTL feature|https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html]. We need a different behavior than what ddb promises: [cleaning once a day with a background job|https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/howitworks-ttl.html] is not usable for this feature - although it can be used as a general cleanup solution separately and independently from S3Guard.
> * Use the same ttl for entries and authoritative directory listing
> * All entries can be expired. Then the returned metadata from the MS will be null.
> * Add two new methods pruneExpiredTtl() and pruneExpiredTtl(String keyPrefix) to MetadataStore interface. These methods will delete all expired metadata from the ms.
> * Use last_updated field in ms for both file metadata and authoritative directory expiry.



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