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https://issues.apache.org/jira/browse/HBASE-2468?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12873079#action_12873079
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HBase Review Board commented on HBASE-2468:
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Message from: "Benoit Sigoure" <[email protected]>
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http://review.hbase.org/r/78/#review91
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src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment515>
Remove the spurious spaces around the parenthesis.
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment516>
No space before `[]' on this line and the previous line.
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment517>
Move the declaration of this variable to line 675 where it's initialized.
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment518>
I'm not sure I understand this comment but it could be because I'm not very
familiar with this part of the code.
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment519>
Do this instead:
if (value == null) {
return true; // don't cache it
}
final String serverAddress = Bytes.toString(value);
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment520>
I don't understand the last part of the comment ("fetch ahead number of
rows in META").
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment521>
No space before `[]'.
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment522>
Wrap the `else' on the previous line.
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment523>
Instead of doing `+ e.getMessage()', pass `e' in second argument.
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment524>
No space before `[]'.
src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java
<http://review.hbase.org/r/78/#comment525>
Remove the second part of the check (tableLogs.values() == null). This
can't happen. If it happens, there's a bug in SoftValueSortedMap and we
shouldn't hide it.
src/test/java/org/apache/hadoop/hbase/client/TestFromClientSide.java
<http://review.hbase.org/r/78/#comment526>
No space before `[]'.
- Benoit
> Improvements to prewarm META cache on clients
> ---------------------------------------------
>
> Key: HBASE-2468
> URL: https://issues.apache.org/jira/browse/HBASE-2468
> Project: HBase
> Issue Type: Improvement
> Components: client
> Reporter: Todd Lipcon
> Assignee: Mingjie Lai
> Fix For: 0.21.0
>
> Attachments: HBASE-2468-trunk.patch
>
>
> A couple different use cases cause storms of reads to META during startup.
> For example, a large MR job will cause each map task to hit meta since it
> starts with an empty cache.
> A couple possible improvements have been proposed:
> - MR jobs could ship a copy of META for the table in the DistributedCache
> - Clients could prewarm cache by doing a large scan of all the meta for the
> table instead of random reads for each miss
> - Each miss could fetch ahead some number of rows in META
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