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Posted to common-issues@hadoop.apache.org by "Quan Li (Jira)" <ji...@apache.org> on 2023/07/15 05:58:00 UTC
[jira] [Comment Edited] (HADOOP-18291) S3A prefetch - Implement LRU cache for SingleFilePerBlockCache
[ https://issues.apache.org/jira/browse/HADOOP-18291?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17743347#comment-17743347 ]
Quan Li edited comment on HADOOP-18291 at 7/15/23 5:57 AM:
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the tests are failing in our internal, can't follow the code, tons of review comments, not sure if reviewers wrote code via review this much comments.
[~mthakur] [~mehakmeet] [~ayushsaxena] [~hexiaoqiao] [~inigoiri]
Can someone fix/revert this
ticket -> let reviewer fix it via review -> still break -> addendum
very tough backporting such
was (Author: quanli):
the tests are failing in our internal, can't follow the code, tons of review comments, not sure if reviewers wrote code via review this much comments.
[~mthakur] [~mehakmeet] [~ayushsaxena] [~hexiaoqiao] [~inigoiri]
Can someone fix/revert this
> S3A prefetch - Implement LRU cache for SingleFilePerBlockCache
> --------------------------------------------------------------
>
> Key: HADOOP-18291
> URL: https://issues.apache.org/jira/browse/HADOOP-18291
> Project: Hadoop Common
> Issue Type: Sub-task
> Affects Versions: 3.4.0
> Reporter: Ahmar Suhail
> Assignee: Viraj Jasani
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.3.9
>
>
> Currently there is no limit on the size of disk cache. This means we could have a large number of files on files, especially for access patterns that are very random and do not always read the block fully.
>
> eg:
> in.seek(5);
> in.read();
> in.seek(blockSize + 10) // block 0 gets saved to disk as it's not fully read
> in.read();
> in.seek(2 * blockSize + 10) // block 1 gets saved to disk
> .. and so on
>
> The in memory cache is bounded, and by default has a limit of 72MB (9 blocks). When a block is fully read, and a seek is issued it's released [here|https://github.com/apache/hadoop/blob/feature-HADOOP-18028-s3a-prefetch/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/read/S3CachingInputStream.java#L109]. We can also delete the on disk file for the block here if it exists.
>
> Also maybe add an upper limit on disk space, and delete the file which stores data of the block furthest from the current block (similar to the in memory cache) when this limit is reached.
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