Mailing-List: contact common-issues-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Date: Sat, 3 Dec 2016 02:11:58 +0000 (UTC)
From: "Mingliang Liu (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Message-ID: <JIRA.12994118.1470096079000.429665.1480731118543@Atlassian.JIRA>
In-Reply-To: <JIRA.12994118.1470096079000@Atlassian.JIRA>
References: <JIRA.12994118.1470096079000@Atlassian.JIRA> <JIRA.12994118.1470096079825@arcas>
Subject: [jira] [Commented] (HADOOP-13449) S3Guard: Implement
 DynamoDBMetadataStore.
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
archived-at: Sat, 03 Dec 2016 02:12:00 -0000


    [ https://issues.apache.org/jira/browse/HADOOP-13449?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15717170#comment-15717170 ] 

Mingliang Liu commented on HADOOP-13449:
----------------------------------------

Yes I did consider putting all the ancestors to the metadata store when putting a single path. Another benefit is that, {{isEmpty}} will be much easier: simply issue a query request (limit return size 1) whose hash key ("parent" field) is the specific directory, and if there is any data returned, the directory is non-empty; else empty. Then the case that {{/a, /a/b/c, /a/b/d}} yet {{/a}} is not empty, does not exist. Plus we don't have to store/maintain the {{isEmpty}} field any longer.

I gave up this constraints when implementing DDB and let the file system enforces this for the sake of performance. Consider a simple case: to {{put(PathMetadata meta)}} 1K files in a deep directory (say 10 layers), every put operation will check if all the ancestors exist, and 1K operation becomes 10K operations to DDB. For {{put(DirListingMetadata meta)}}, it will be efficient so we can blame users for not using this one instead.

So overall, not changing MetadataStore is possible and we can change this in the {{DynamoDBMetadataStore}} implementation. I'll post a patch (may be a wip one) soon.

So we did find real bugs/problems/limitation via integration tests; and they're helpful. Thanks,

> S3Guard: Implement DynamoDBMetadataStore.
> -----------------------------------------
>
>                 Key: HADOOP-13449
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13449
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>            Reporter: Chris Nauroth
>            Assignee: Mingliang Liu
>         Attachments: HADOOP-13449-HADOOP-13345.000.patch, HADOOP-13449-HADOOP-13345.001.patch, HADOOP-13449-HADOOP-13345.002.patch, HADOOP-13449-HADOOP-13345.003.patch, HADOOP-13449-HADOOP-13345.004.patch, HADOOP-13449-HADOOP-13345.005.patch, HADOOP-13449-HADOOP-13345.006.patch, HADOOP-13449-HADOOP-13345.007.patch, HADOOP-13449-HADOOP-13345.008.patch, HADOOP-13449-HADOOP-13345.009.patch, HADOOP-13449-HADOOP-13345.010.patch
>
>
> Provide an implementation of the metadata store backed by DynamoDB.


--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

---------------------------------------------------------------------
To unsubscribe, e-mail: common-issues-unsubscribe@hadoop.apache.org
For additional commands, e-mail: common-issues-help@hadoop.apache.org