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

[zhihai xu (JIRA)]

zhihai xu created YARN-3727:
-------------------------------

             Summary: 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


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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