IMPALA-4029: [DOCS] Include known issue for 'flat buffers' change

Change-Id: I65495748984268763b2690c193488a338409e13e
Reviewed-on: http://gerrit.cloudera.org:8080/7236
Reviewed-by: John Russell <[email protected]>
Tested-by: Impala Public Jenkins


Project: http://git-wip-us.apache.org/repos/asf/incubator-impala/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-impala/commit/91dbeb3c
Tree: http://git-wip-us.apache.org/repos/asf/incubator-impala/tree/91dbeb3c
Diff: http://git-wip-us.apache.org/repos/asf/incubator-impala/diff/91dbeb3c

Branch: refs/heads/master
Commit: 91dbeb3c061292c832b069bdf07fb76533332f23
Parents: 384e864
Author: John Russell <[email protected]>
Authored: Tue Jun 20 14:27:19 2017 -0700
Committer: Impala Public Jenkins <[email protected]>
Committed: Tue Jun 27 00:17:03 2017 +0000

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 docs/topics/impala_known_issues.xml | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)
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http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/91dbeb3c/docs/topics/impala_known_issues.xml
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diff --git a/docs/topics/impala_known_issues.xml 
b/docs/topics/impala_known_issues.xml
index 75c9d2d..c3f1e51 100644
--- a/docs/topics/impala_known_issues.xml
+++ b/docs/topics/impala_known_issues.xml
@@ -564,6 +564,32 @@ https://issues.apache.org/jira/browse/IMPALA-2144 - Don't 
have
 
     </conbody>
 
+    <concept id="flatbuffers_mem_usage">
+      <title>Memory usage when compact_catalog_topic flag enabled</title>
+      <conbody>
+        <p>
+          The efficiency improvement from <xref 
keyref="IMPALA-4029">IMPALA-4029</xref>
+          can cause an increase in size of the updates to Impala catalog 
metadata
+          that are broadcast to the <cmdname>impalad</cmdname> daemons
+          by the <cmdname>statestored</cmdname> daemon.
+          The increase in catalog update topic size results in higher CPU and 
network
+          utilization. By default, the increase in topic size is about 5-7%. 
If the
+          <codeph>compact_catalog_topic</codeph> flag is used, the
+          size increase is more substantial, with a topic size approximately 
twice as
+          large as in previous versions.
+        </p>
+        <p><b>Bug:</b> <xref keyref="IMPALA-5500">IMPALA-5500</xref></p>
+        <p><b>Severity:</b> Medium</p>
+        <p>
+          <b>Workaround:</b> Consider leaving the 
<codeph>compact_catalog_topic</codeph>
+          configuration setting at its default value of <codeph>false</codeph> 
until
+          this issue is resolved.
+        </p>
+        <p><b>Resolution:</b> A fix is in the pipeline. Check the status of
+        <xref keyref="IMPALA-5500">IMPALA-5500</xref> for the release where 
the fix is available.</p>
+      </conbody>
+    </concept>
+
     <concept id="drop_table_purge_s3a">
       <title>DROP TABLE PURGE on S3A table may not delete externally written 
files</title>
       <conbody>

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