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Date: Wed, 1 Feb 2017 00:58:52 +0000 (UTC)
From: "Manoj Govindassamy (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.13037922.1485398222000.4602.1485910732316@Atlassian.JIRA>
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Subject: [jira] [Commented] (HDFS-11370) Optimize
 NamenodeFsck#getReplicaInfo
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archived-at: Wed, 01 Feb 2017 00:59:13 -0000


    [ 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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