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From "Aaron Fabbri (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13452) S3Guard: Implement access policy for intra-client consistency with in-memory metadata store.
Date Tue, 20 Sep 2016 19:17:20 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13452?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15507496#comment-15507496

Aaron Fabbri commented on HADOOP-13452:

Thanks for review [~liuml07].

{quote}Is the LruHashMap always supposed to access the entries via mruGet()? {quote}

I was trying to have the flexibility of allowing caller to only call get() when it doesn't
need to MRU the entry.  I only use the plain get() once, and you could argue it could be an
mruGet() instead.

{quote}And for fixed size, we can override the removeEldestEntry() method.{quote}
I do that. This code looks the same as mine, except I do not override load factor to 1.0 (which
saves space at expense of runtime).

{quote}Basically we can simply make operating methods synchronized instead of synchronized
blocks? This should improve readability if no obvious performance loss.{quote}

I can do that for the functions where the critical section is the whole method.  I like the
explicit block style (often I don't notice synchronized in signatures for some reason), but
I'm happy to change it.  I don't think it is addressed in style guide.

Or can we simply use the off-the-shelf org.apache.commons.collections.map.LRUMap
I didn't know that existed.  I'm happy to use it.  One concern is that it subclasses a deprecated,
non-Java API linked hash map implementation. 

> S3Guard: Implement access policy for intra-client consistency with in-memory metadata
> --------------------------------------------------------------------------------------------
>                 Key: HADOOP-13452
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13452
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>            Reporter: Chris Nauroth
>            Assignee: Aaron Fabbri
>         Attachments: HADOOP-13452.001.patch
> Implement an S3A access policy based on an in-memory metadata store.  This can provide
consistency within the same client without needing to integrate with an external system.

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