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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-17140) Reduce meta request number by skipping table state check
Date Wed, 30 Nov 2016 03:02:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-17140?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15707341#comment-15707341

Enis Soztutar commented on HBASE-17140:

We have to be careful here table disabled and region offline are different concepts. In the
current code, region offline can mean two things (depending on meta or AM context): 
(1) Region is not assigned yet. 
(2) Region is no more "assignable", meaning the region is split or merged. 

In the case of (2), the HRI for parent region is saved with split=true, offline=true (similar
for merge). If we are marking every region to be offline in a disable table, we have to be
careful of this double meaning. When the table is re-enabled again, we do not want to bring
back the old parents. 

Can we instead do a multi-get to meta for getting the table state and the region location
everytime? This way there will be a single RPC to the meta table returning both the result
of table state and the region location. 

> Reduce meta request number by skipping table state check
> --------------------------------------------------------
>                 Key: HBASE-17140
>                 URL: https://issues.apache.org/jira/browse/HBASE-17140
>             Project: HBase
>          Issue Type: Improvement
>          Components: Client
>    Affects Versions: 2.0.0
>            Reporter: Guanghao Zhang
>            Assignee: Guanghao Zhang
>         Attachments: HBASE-17140-v1.patch, HBASE-17140-v2.patch, HBASE-17140-v3.patch,
HBASE-17140-v4.patch, HBASE-17140-v5.patch
> Now when request for a disabled table, it need 3 rpc calls before fail.
> 1. get region location
> 2. send call to rs and get NotServeRegionException
> 3. retry and check the table state, then throw TableNotEnabledException
> The table state check is added for disabled table. But now the prepare method in RegionServerCallable
shows that all retry request will get table state first.
> {code}
> public void prepare(final boolean reload) throws IOException {
>     // check table state if this is a retry
>     if (reload && !tableName.equals(TableName.META_TABLE_NAME) &&
>         getConnection().isTableDisabled(tableName)) {
>       throw new TableNotEnabledException(tableName.getNameAsString() + " is disabled.");
>     }
>     try (RegionLocator regionLocator = connection.getRegionLocator(tableName)) {
>       this.location = regionLocator.getRegionLocation(row);
>     }
>     if (this.location == null) {
>       throw new IOException("Failed to find location, tableName=" + tableName +
>           ", row=" + Bytes.toString(row) + ", reload=" + reload);
>     }
>     setStubByServiceName(this.location.getServerName());
> }
> {code}
> An improvement is set the region offline in HRegionInfo and throw the RegionOfflineException
when get region location. Then we don't need check table state for any retry request.
> Review board: https://reviews.apache.org/r/54071/

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