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From "Grant Henke (Code Review)" <ger...@cloudera.org>
Subject [kudu-CR] KUDU-1802: Avoid calls to master when using scan tokens
Date Tue, 30 Jun 2020 12:45:45 GMT
Grant Henke has submitted this change and it was merged. ( http://gerrit.cloudera.org:8080/16031
)

Change subject: KUDU-1802: Avoid calls to master when using scan tokens
......................................................................

KUDU-1802: Avoid calls to master when using scan tokens

This patch adds new metadata to the scan token to allow it
to contain all of the metadata required to construct a KuduTable
and open a scanner in the clients. This means the GetTableSchema
and GetTableLocations RPC calls to the master are no longer required
when using the scan token.

New TableMetadataPB, TabletMetadataPB, and authorization token
fields were added as optional fields on the token. Additionally a
`projected_column_idx` field was added that can be used in place
of the `projected_columns`. This significantly reduces the size of
the scan token by not duplicating the ColumnSchemaPB that is
already in the TableMetadataPB.

Adding the table metadata to the scan token is enabled by
default given it’s more scalable and performant. However,
it can be disabled in rare cases where more resiliency to
column renaming is desired. One example where disabling the
table metadata is used is the backup job. Future work, tracked
by KUDU-3146, should allow for table metadata to be leveraged in
those cases as well.

This doesn’t avoid the need for a call to the master to get the
schema in the case of writing data to Kudu, that work is tracked
by KUDU-3135. I expect the TableMetadataPB message would
be used there as well.

I included the ability to disable this functionality in the
kudu-spark integration via `kudu.useDriverMetadata` just
in case there are any unforeseen issues or regressions with
this feature.

I added a test to compare the serialized size of the scan token with
and without the table and tablet metadata. The size results for a
100 column table are:
   no metadata: 2697 Bytes
   tablet metadata: 2805
   tablet, table, and authz metadata: 3258

Change-Id: I88c1b8392de37dd5e8b7bd8b78a21603ff8b1d1b
Reviewed-on: http://gerrit.cloudera.org:8080/16031
Reviewed-by: Grant Henke <granthenke@apache.org>
Tested-by: Grant Henke <granthenke@apache.org>
---
M java/kudu-backup/src/main/scala/org/apache/kudu/backup/KuduBackupRDD.scala
M java/kudu-client/src/main/java/org/apache/kudu/client/AsyncKuduClient.java
M java/kudu-client/src/main/java/org/apache/kudu/client/KuduScanToken.java
M java/kudu-client/src/main/java/org/apache/kudu/client/ProtobufHelper.java
M java/kudu-client/src/main/java/org/apache/kudu/client/RemoteTablet.java
M java/kudu-client/src/main/java/org/apache/kudu/client/TableLocationsCache.java
M java/kudu-client/src/test/java/org/apache/kudu/client/TestScanToken.java
M java/kudu-spark/src/main/scala/org/apache/kudu/spark/kudu/DefaultSource.scala
M java/kudu-spark/src/main/scala/org/apache/kudu/spark/kudu/KuduRDD.scala
M java/kudu-spark/src/main/scala/org/apache/kudu/spark/kudu/KuduReadOptions.scala
M src/kudu/client/CMakeLists.txt
M src/kudu/client/client.cc
M src/kudu/client/client.h
M src/kudu/client/client.proto
M src/kudu/client/meta_cache.cc
M src/kudu/client/meta_cache.h
M src/kudu/client/scan_token-internal.cc
M src/kudu/client/scan_token-internal.h
M src/kudu/client/scan_token-test.cc
19 files changed, 1,024 insertions(+), 136 deletions(-)

Approvals:
  Grant Henke: Looks good to me, approved; Verified

-- 
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: I88c1b8392de37dd5e8b7bd8b78a21603ff8b1d1b
Gerrit-Change-Number: 16031
Gerrit-PatchSet: 21
Gerrit-Owner: Grant Henke <granthenke@apache.org>
Gerrit-Reviewer: Alexey Serbin <aserbin@cloudera.com>
Gerrit-Reviewer: Andrew Wong <awong@cloudera.com>
Gerrit-Reviewer: Grant Henke <granthenke@apache.org>
Gerrit-Reviewer: Greg Solovyev <gsolovyev@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins (120)
Gerrit-Reviewer: Tidy Bot (241)
Gerrit-Reviewer: Todd Lipcon <todd@apache.org>

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