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https://issues.apache.org/jira/browse/HADOOP-20066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18138463#comment-18138463
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ASF GitHub Bot commented on HADOOP-20066:
-----------------------------------------
LuciferYang opened a new pull request, #8930:
URL: https://github.com/apache/hadoop/pull/8930
### Description of PR
JIRA: https://issues.apache.org/jira/browse/HADOOP-20066
For an unknown size, `AllocatorPerContext#getLocalPathForWrite` picks a
directory at random, weighted by free space, and subtracts a directory's space
from `totalAvailable` when `createPath()` fails for it. A directory with no
usable space still counts toward `numDirs`, so after every directory with space
has failed, `totalAvailable` is 0 while the loop still runs, and `(r.nextLong()
>>> 1) % totalAvailable` throws `ArithmeticException: / by zero` instead of the
`DiskErrorException` that lists the directories. One full disk plus a disk
remounted read-only is enough, and since the context is only rebuilt when the
configuration changes, every such allocation in that JVM fails the same way.
This patch adds `totalAvailable > 0` to the loop condition, so the existing
`DiskErrorException` is thrown. HADOOP-9079 proposed the same change in 2012,
but it was not committed.
### How was this patch tested?
Added `TestLocalDirAllocator#testGetLocalPathForWriteWhenAllDirsFailCreate`
(parameterized like its neighbours): one buffer directory is removed and cannot
be recreated, the other is made read-only, and `getLocalPathForWrite` must
throw `DiskErrorException` naming both. Without the fix it throws
`ArithmeticException`.
### For code changes:
- [x] Does the title of this PR start with the corresponding JIRA issue id
(e.g. 'HADOOP-17799. Your PR title ...')?
- [ ] Object storage: Have the integration tests been executed and the
endpoint declared according to the connector-specific documentation?
- [ ] If adding new dependencies to the code, are these dependencies
licensed in a way that is compatible for inclusion under [ASF
2.0](http://www.apache.org/legal/resolved.html#category-a)?
- [ ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`,
`NOTICE-binary` files?
### AI Tooling
- [x] The PR includes the phrase "Contains content generated by Claude Opus".
- [x] My use of AI contributions follows the ASF legal policy
https://www.apache.org/legal/generative-tooling.html
Contains content generated by Claude Opus.
> LocalDirAllocator throws ArithmeticException instead of DiskErrorException
> when every directory with free space fails the write check
> -------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HADOOP-20066
> URL: https://issues.apache.org/jira/browse/HADOOP-20066
> Project: Hadoop Common
> Issue Type: Bug
> Components: fs
> Reporter: Yang Jie
> Priority: Minor
>
> When the size is unknown, AllocatorPerContext#getLocalPathForWrite picks a
> directory at random, weighted by its free space. If the chosen directory
> fails createPath(), its space is subtracted from {{totalAvailable}} and it
> counts as searched. A directory with no usable space still counts toward
> {{numDirs}}, so after every directory with space has failed,
> {{totalAvailable}} is 0 while {{numDirsSearched < numDirs}} still holds, and
> the next {{(r.nextLong() >>> 1) % totalAvailable}} throws
> "ArithmeticException: / by zero".
> This needs two or more directories, at least one with no usable space, and
> every directory with space failing createPath(), for example a disk remounted
> read-only. The allocator only rebuilds its context when the configuration
> changes, so in a task or client JVM every such allocation fails from then on.
> Callers expect a DiskErrorException, which is an IOException; they get an
> unchecked exception instead, without the message that lists the directories.
> The fix stops the loop once no space is left, so the existing
> DiskErrorException is thrown. HADOOP-9079 reported this case in 2012 with the
> same change, but it was never committed.
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