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From "Anu Engineer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11119) Support for parallel checking of StorageLocations on DataNode startup
Date Wed, 09 Nov 2016 20:44:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15651987#comment-15651987
] 

Anu Engineer commented on HDFS-11119:
-------------------------------------

[~arpitagarwal] Thanks for the patch. Some minor comments

The way time is specified is little confusing. Just wanted to make sure that my understanding
is correct.
{noformat}
public static final String DFS_DATANODE_DISK_CHECK_TIMEOUT_DEFAULT ="10m";
public static final String DFS_DATANODE_DISK_CHECK_MIN_GAP_DEFAULT ="15m";
{noformat} 
This is milliseconds right ?  but if that is hardcoded in code, then why take an "m" if all
of these are time units in milliseconds.

 When I first read code I read 15m as 15 minutes and later realized that it is 15 milliseconds.
I think we should pick a larger min gap and also if possible specify that the time unit is
not flexible. 

In hdfs-default.xml also can we specify that the time unit is in milliseconds. It is obvious
from code, but I am worried some user might try to specify something like H.

{{StorageLocationsChecker.java#check}}

{noformat}
    if (goodLocations.size() == 0) {
      throw new IOException("All directories in "
          + DFS_DATANODE_DATA_DIR_KEY + " are invalid: "
          + failedLocations);
    }
{noformat} 
Should we Log.error this case too  ?

{{StorageLocationsChecker.java}}
  Executors.newCachedThreadPool()
Can we a ThreadFactory so we can set the name of threads in this pool ? Plus, Are these threads
daemons ? 

nit : I am presuming the change in Datanode startup is coming in a later patch ?  


> Support for parallel checking of StorageLocations on DataNode startup
> ---------------------------------------------------------------------
>
>                 Key: HDFS-11119
>                 URL: https://issues.apache.org/jira/browse/HDFS-11119
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode
>            Reporter: Arpit Agarwal
>            Assignee: Arpit Agarwal
>
> The {{AsyncChecker}} support introduced by HDFS-11114 can be used to parallelize checking
{{StorageLocation}} s on Datanode startup.



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