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From "Yi Liang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-18109) Assign system tables first (priority)
Date Wed, 07 Jun 2017 19:18:19 GMT

    [ https://issues.apache.org/jira/browse/HBASE-18109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16041461#comment-16041461
] 

Yi Liang commented on HBASE-18109:
----------------------------------

Hi [~stack], 
 :(, another problem comes, in TableDescriptor, we already have a set of Priority, but the
priority is for RPC
{code}
  /**
   * Relative priority of the table used for rpc scheduling
   */
  private static final int DEFAULT_PRIORITY = HConstants.NORMAL_QOS;
{code}

So, I am not sure it is good to add another set of priority.  

After fully review the code, I think original author has already made meta and system table
assigned first.
He use a queue called FairQueue to schedule procedures, and there are two factors that may
affect the rate of procedure in the queue to be scheduled, one is procedure priority and other
is the position of the procedure in the FairQueue, any procedures with high priority(he add
priority in MasterProcedureScheduler, not in table) will be scheduled with high rate and also
procedures in front/head of FairQueue also has high rate to be scheduled. 

Since original author has already make sure "meta/system table will be assigned first with
higher rate"; I think  that will be enough for this jira, or we need to change how ProcedureExcutor
schedule procedures. As for Phil's problem, we can open another jira for it, cause it is not
very related to AM, lets now focus more on ProcedureV2 AM.

(My old patch just make simple distinction between system table and user table, it will put
system table in front/head of FairQueue, which can theoretically help to assign system table
first. If you like it, we can add it into current implementation)







> Assign system tables first (priority)
> -------------------------------------
>
>                 Key: HBASE-18109
>                 URL: https://issues.apache.org/jira/browse/HBASE-18109
>             Project: HBase
>          Issue Type: Sub-task
>          Components: Region Assignment
>    Affects Versions: 2.0.0
>            Reporter: stack
>            Assignee: Yi Liang
>            Priority: Critical
>             Fix For: 2.0.0
>
>         Attachments: HBASE-18109-V1.patch
>
>
> Need this for stuff like the RSGroup table, etc. Assign these ahead of user-space regions.
> From 'Handle sys table assignment first (e.g. acl, namespace, rsgroup); currently only
hbase:meta is first.' of https://docs.google.com/document/d/1eVKa7FHdeoJ1-9o8yZcOTAQbv0u0bblBlCCzVSIn69g/edit#heading=h.oefcyphs0v0x



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