[jira] [Commented] (YARN-3727) For better error recovery, check if the directory exists before using it for localization.

["Chang Li (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-3727?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14935272#comment-14935272 ] 

Chang Li commented on YARN-3727:
--------------------------------

+1 (non binding)

> For better error recovery, check if the directory exists before using it for localization.
> ------------------------------------------------------------------------------------------
>
>                 Key: YARN-3727
>                 URL: https://issues.apache.org/jira/browse/YARN-3727
>             Project: Hadoop YARN
>          Issue Type: Improvement
>          Components: nodemanager
>    Affects Versions: 2.7.0
>            Reporter: zhihai xu
>            Assignee: zhihai xu
>         Attachments: YARN-3727.000.patch
>
>
> For better error recovery, check if the directory exists before using it for localization.
> We saw the following localization failure happened due to existing cache directories.
> {code}
> 2015-05-11 18:59:59,756 INFO org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.ResourceLocalizationService: DEBUG: FAILED { hdfs://XXXX/XXXXX/libjars/1234.jar, 1431395961545, FILE, null }, Rename cannot overwrite non empty destination directory /XXXX/8/yarn/nm/usercache/XXXX/filecache/21637
> 2015-05-11 18:59:59,756 INFO org.apache.hadoop.yarn.server.nodemanager.containermanager.localizer.LocalizedResource: Resource hdfs://XXXX/XXXXX/libjars/1234.jar(->/XXXX/8/yarn/nm/usercache/XXXX/filecache/21637/1234.jar) transitioned from DOWNLOADING to FAILED
> {code}
> The real cause for this failure may be disk failure, LevelDB operation failure for {{startResourceLocalization}}/{{finishResourceLocalization}} or others.
> I wonder whether we can add error recovery code to avoid the localization failure by not using the existing cache directories for localization.
> The exception happened at {{files.rename(dst_work, destDirPath, Rename.OVERWRITE)}} in FSDownload#call. Based on the following code, after the exception, the existing cache directory used by {{LocalizedResource}} will be deleted.
> {code}
> try {
>      .........
>       files.rename(dst_work, destDirPath, Rename.OVERWRITE);
>     } catch (Exception e) {
>       try {
>         files.delete(destDirPath, true);
>       } catch (IOException ignore) {
>       }
>       throw e;
>     } finally {
> {code}
> Since the conflicting local directory will be deleted after localization failure,
> I think it will be better to check if the directory exists before using it for localization to avoid the localization failure.



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