Add new key generator "LeafSegmentKeyGenerator" and related functions.

[wgy8283335]

Fixes #1775.

Changes proposed in this pull request:

• Add new key generator "LeafSegmentKeyGenerator" and related functions.

[wgy8283335]

@terrymanu .
The test failed, due to LeafSegmentKeyGenrator test depends on zookeeper. Do u have any suggestion for me?
13:26:17.983 [pool-1-thread-1-SendThread(127.0.0.1:2181)] DEBUG org.apache.zookeeper.ClientCnxnSocketNIO - Ignoring exception during shutdown output
java.nio.channels.ClosedChannelException: null
at sun.nio.ch.SocketChannelImpl.shutdownOutput(SocketChannelImpl.java:797)
at sun.nio.ch.SocketAdaptor.shutdownOutput(SocketAdaptor.java:407)
at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:207)
at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1185)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1110)

[terrymanu]

You can try to use curator-test which can startup a zookeeper in memory, or use mock to do unit-test

[wgy8283335]

@terrymanu .THX, I will try it later.

[coveralls]

Pull Request Test Coverage Report for Build 8249

• 97 of 138 (70.29%) changed or added relevant lines in 4 files are covered.
• 234 unchanged lines in 20 files lost coverage.
• Overall coverage increased (+0.2%) to 60.843%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
sharding-core/sharding-core-common/src/main/java/org/apache/shardingsphere/core/strategy/keygen/LeafSegmentKeyGenerator.java	48	54	88.89%
sharding-core/sharding-core-common/src/main/java/org/apache/shardingsphere/core/strategy/keygen/LeafExceptionHandler.java	0	10	0.0%
sharding-core/sharding-core-common/src/main/java/org/apache/shardingsphere/core/strategy/keygen/LeafCuratorZookeeper.java	41	66	62.12%

Files with Coverage Reduction	New Missed Lines	%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/sql/segment/dml/order/item/ExpressionOrderByItemSegment.java	1	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/sql/segment/dml/order/item/ColumnOrderByItemSegment.java	2	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/filler/common/dml/OrderByFiller.java	2	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/filler/common/dml/GroupByFiller.java	2	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/sql/segment/dml/order/item/OrderByItemSegment.java	4	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/sql/statement/dml/SelectStatement.java	5	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/sql/segment/dml/order/item/IndexOrderByItemSegment.java	5	0.0%
sharding-proxy/sharding-proxy-frontend/sharding-proxy-frontend-postgresql/src/main/java/org/apache/shardingsphere/shardingproxy/frontend/postgresql/command/query/binary/parse/PostgreSQLComParseExecutor.java	6	0.0%
sharding-core/sharding-core-parse/sharding-core-parse-common/src/main/java/org/apache/shardingsphere/core/parse/sql/segment/dml/column/ColumnSegment.java	7	0.0%
sharding-core/sharding-core-rewrite/src/main/java/org/apache/shardingsphere/core/rewrite/rewriter/ShardingSQLRewriter.java	8	74.24%

Totals
Change from base Build 8228:	0.2%
Covered Lines:	8167
Relevant Lines:	13423

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💛 - Coveralls

[terrymanu]

Nice work, thank you.
Let @tristaZero to review it.

[tristaZero]

@wgy8283335 Thanks, i think it is great after a quick look.
I will give you feedback as soon sa possiable.

[wgy8283335]

@tristaZero. Thank you.

[tristaZero]

@wgy8283335

After reading your pr carefully and digging into the Leaf-segement and Leaf-Snowflake, i give my opinions about this pr, and also want to have
a discuss in detail with you, please let me know your feedback. Thanks.

1.The package of sharding-core-common should be basic package which is used by other packages, so it is better to move all the classes related to LeafSegmentKeyGenerator to sharding-orchestration-core.

2.When LeafSegmentKeyGenerator is in sharding-orchestration-core, maybe we can consider to use CuratorZookeeperRegistryCenter instead of LeafCuratorZookeeper. The function of incrementCacheId in LeafCuratorZookeeper can considered to move to LeafSegmentKeyGenerator, and moving tryLock() to CuratorZookeeperRegistryCenter is ok?

3.The API of generateKey() now is to return null in LeafSegmentKeyGenerator, but it is not allowed to modify APIs. Therefore using generateKey(), not generateKey(tableName) is a better choice.

4.Actually, LeafSegmentKeyGenerator really needs tableName as a key in zk. So i suggest set tableName in properties of LeafSegmentKeyGenerator and getTableName() from properties to use it in zk.

5.The another important thing is multiple schemas. If user use same tableName in multiple schemas, the node value of same table name in zk will be overwrite. So please consider use schemaName and tableName as note key.