[Impala-ASF-CR] IMPALA-4765: Avoid using several loading threads on one table.

["Alex Behm (Code Review)" <ge...@cloudera.org>]

Hello Bharath Vissapragada,

I'd like you to reexamine a change.  Please visit

    http://gerrit.cloudera.org:8080/5707

to look at the new patch set (#2).

Change subject: IMPALA-4765: Avoid using several loading threads on one table.
......................................................................

IMPALA-4765: Avoid using several loading threads on one table.

When there are multiple concurrent requests to the catalogd to
prioritize loading the same table, then several catalog loading
threads may end up waiting for that single table to be loaded,
effectively reducing the number of catalog loading threads. In
extreme examples, this might degrade to serial loading of tables.

This patch augments the existing data structures and code to
prevent using several loading threads for the same table.
Some of the existing data structures and code could be
consolidated/simplified but this patch does not try to address
that issue to minimize the risk of this change.

Testing: I could easily reproduce the bug locally with the steps
described in the JIRA. After this patch, I could not observe threads
being wasted anymore.

Change-Id: Idba5f1808e0b9cbbcf46245834d8ad38d01231cb
---
M fe/src/main/java/org/apache/impala/catalog/TableLoadingMgr.java
1 file changed, 34 insertions(+), 19 deletions(-)


  git pull ssh://gerrit.cloudera.org:29418/Impala-ASF refs/changes/07/5707/2
-- 
To view, visit http://gerrit.cloudera.org:8080/5707
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Idba5f1808e0b9cbbcf46245834d8ad38d01231cb
Gerrit-PatchSet: 2
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Alex Behm <al...@cloudera.com>
Gerrit-Reviewer: Alex Behm <al...@cloudera.com>
Gerrit-Reviewer: Bharath Vissapragada <bh...@cloudera.com>
Gerrit-Reviewer: Jim Apple <jb...@apache.org>
Gerrit-Reviewer: Tim Armstrong <ta...@cloudera.com>