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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4882) Drill does not work when it has only access to "secondary nodes"
Date Wed, 04 Jan 2017 23:24:58 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15799679#comment-15799679
] 

ASF GitHub Bot commented on DRILL-4882:
---------------------------------------

Github user chunhui-shi commented on a diff in the pull request:

    https://github.com/apache/drill/pull/609#discussion_r94686987
  
    --- Diff: contrib/storage-mongo/src/main/resources/bootstrap-storage-plugins.json ---
    @@ -3,7 +3,8 @@
         mongo : {
           type:"mongo",
           enabled: false,
    -      connection:"mongodb://localhost:27017/"
    +      connection:"mongodb://localhost:27017/",
    +      "direct-connection" : false
         }
    --- End diff --
    
    Could you make "direct-connection" optional but default to false?


> Drill does not work when it has only access to "secondary nodes"
> ----------------------------------------------------------------
>
>                 Key: DRILL-4882
>                 URL: https://issues.apache.org/jira/browse/DRILL-4882
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Storage - MongoDB
>    Affects Versions: 1.6.0, 1.7.0, 1.8.0
>         Environment: Drill Stand Alone
> Drill in MapR
>            Reporter: Tugdual Grall
>            Priority: Minor
>
> In some deployments, especially when doing analytics on MongoDB, the application, Drill
in this case, only have access to secondary nodes. 
> This is a common choice to avoid overloading the Mongo cluster.
> When we have such configuration Drill fail with various exception related to timeout/primary
read preference.
> This is due to the fact that some of the "Schema Oriented" methods of MongoDriver are
forcing the read preference to primary. The methods are used in the following place in Drill:
> 1-
> https://github.com/apache/drill/blob/1.8.0/contrib/storage-mongo/src/main/java/org/apache/drill/exec/store/mongo/schema/MongoSchemaFactory.java#L89
> 2-
> https://github.com/apache/drill/blob/1.8.0/contrib/storage-mongo/src/main/java/org/apache/drill/exec/store/mongo/schema/MongoSchemaFactory.java#L109
> and also the Run command to get information about the type of topology (sharded or not):
> 3- 
> https://github.com/apache/drill/blob/1.8.0/contrib/storage-mongo/src/main/java/org/apache/drill/exec/store/mongo/MongoGroupScan.java#L167
> 3- could be fixed by simply adding a ReadPreference.primaryPreferred() but not sufficient
since we need to have 1 & 2 fixed



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