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From "Manoj Govindassamy (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11370) Optimize NamenodeFsck#getReplicaInfo
Date Wed, 01 Feb 2017 00:58:52 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15847826#comment-15847826
] 

Manoj Govindassamy commented on HDFS-11370:
-------------------------------------------

Thanks [~tasanuma0829]. 

bq. I think it is the same risk as that of BlockUnderConstructionFeature#getExpectedStorageLocations()
at least.

{{BlockUnderConstructionFeature#getExpectedStorageLocations()}} and few other public methods
in the same class work on the {{replicas}} array without proper synchronization but they never
expose the cursor on the array to the caller. With {{getExpectedStorageLocationsIterator()}}
we will be exposing a public iterator with the cursor exposed, but not thread safe. As a general
practice, its advisable not to introduce any new non thread safe public iterators. One workaround
here i can think of is, since the replicas is a very small array, we can have a copy of the
replicas in the iterator at the time of construction and iterate over the same. Your thoughts
please ?

> Optimize NamenodeFsck#getReplicaInfo
> ------------------------------------
>
>                 Key: HDFS-11370
>                 URL: https://issues.apache.org/jira/browse/HDFS-11370
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>            Reporter: Takanobu Asanuma
>            Assignee: Takanobu Asanuma
>            Priority: Minor
>         Attachments: HDFS-11370.1.patch, HDFS-11370.2.patch, HDFS-11370.3.patch, HDFS-11370.4.patch,
HDFS-11370.5.patch
>
>
> We can optimize the logic of calculating the number of storages in {{NamenodeFsck#getReplicaInfo}}.
This is a follow-on task of HDFS-11124.



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