[HUDI-3730][RFC-55] Improve hudi-sync classes design and simplify configs

rfc/rfc-55/rfc-55.md

@@ -0,0 +1,157 @@
+<!--
+  Licensed to the Apache Software Foundation (ASF) under one or more
+  contributor license agreements.  See the NOTICE file distributed with
+  this work for additional information regarding copyright ownership.
+  The ASF licenses this file to You under the Apache License, Version 2.0
+  (the "License"); you may not use this file except in compliance with
+  the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+-->
+# RFC-55: Improve hudi-sync classes design and simplify configs
+
+## Proposers
+
+- @<proposer1 @fengjian428>
+- @<proposer2 @xushiyan>
+
+## Approvers
+
+ - @<approver1 @vinothchandar>
+ - @<approver2 @codope>
+
+## Status
+
+JIRA: [HUDI-3730](https://issues.apache.org/jira/browse/HUDI-3730)
+
+## Abstract
+
+![hudi-sync-flows.png](hudi-sync-flows.png)
+
+Hudi support sync to various metastores via different processing framework like Spark, Flink, and Kafka connect. 
+
+There are some room for improvement
+
+* The way to generate Sync configs are inconsistent in different framework
+* The abstraction of SyncClasses was designed for HiveSync, hence there are duplicated code, unused method, and parameters.
+
+We need a standard way to run hudi sync. We also need a unified abstraction of XXXSyncTool , XXXSyncClient and XXXSyncConfig to handle supported metastores, like hive metastore, bigquery, datahub, etc.
+
+## Classes design
+
+![hudi-sync-class-diagram.png](hudi-sync-class-diagram.png)
+
+Below are the proposed key classes to handle the main sync logic. They are extensible for different metastores.
+
+### `HoodieSyncTool`
+
+*Renamed from `AbstractSyncTool`.*
+
+```java
+public abstract class HoodieSyncTool implements AutoCloseable {
+
+  protected HoodieSyncClient syncClient;
+
+  /**
+   * Sync tool class is the entrypoint to run meta sync.
+   *
+   * @param props A bag of properties passed by users. It can contain all hoodie.* and any other config.
+   * @param hadoopConf Hadoop specific configs.
+   */
+  public HoodieSyncTool(Properties props, Configuration hadoopConf);
+
+  public abstract void syncHoodieTable();
+
+  public static void main(String[] args) {
+     // instantiate HoodieSyncConfig and concrete sync tool, and run sync.
+  }
+}
+```
+
+### `HoodieSyncConfig`
+
+```java
+public class HoodieSyncConfig extends HoodieConfig {
+
+  public static class HoodieSyncConfigParams {
+    // POJO class to take command line parameters
+    @Parameter()
+    private String basePath; // common essential parameters
+
+    public Properties toProps();
+  }
+
+   /**
+    * XXXSyncConfig is meant to be created and used by XXXSyncTool exclusively and internally.
+    * 
+    * @param props passed from XXXSyncTool.
+    * @param hadoopConf passed from XXXSyncTool.
+    */
+  public HoodieSyncConfig(Properties props, Configuration hadoopConf);
+}
+
+public class HiveSyncConfig extends HoodieSyncConfig {
+
+  public static class HiveSyncConfigParams {
+
+    @Parameter()
+    private String syncMode;
+
+    // delegate common parameters to other XXXParams class
+    // this overcomes single-inheritance's inconvenience
+    // see https://jcommander.org/#_parameter_delegates
+    @ParametersDelegate()
+    private HoodieSyncConfigParams hoodieSyncConfigParams = new HoodieSyncConfigParams();
+
+    public Properties toProps();
+  }
+
+  public HoodieSyncConfig(Properties props);
+}
+```
+
+### `HoodieSyncClient`
+
+*Renamed from `AbstractSyncHoodieClient`.*
+
+```java
+public abstract class HoodieSyncClient implements AutoCloseable {
+  // metastore-agnostic APIs
+}
+```
+
+## Config simplification
+
+- rename all sync related configs to suffix as `hoodie.sync.*`
+  - no more `hoodie.meta.sync.*` or `hoodie.meta_sync.*`
+  - no more variable name or class name like `metaSyncEnabled` or `metaSyncTool`; standardize as `hoodieSync*` to align with module name `hudi-sync`
+- remove all sync related option constants from `DataSourceOptions`
+- `database` and `table` should not be required by sync tool; they should be inferred from table properties
+- users should not need to set PartitionValueExtractor; partition values should be inferred automatically
+- remove `USE_JDBC` and fully adopt `SYNC_MODE`
+- remove `HIVE_SYNC_ENDABLED` and related arguments from sync tools and delta streamers. Use `SYNC_ENABLED`
+- migrate repeated sync config to original config
+   - `META_SYNC_BASE_FILE_FORMAT` -> `org.apache.hudi.common.table.HoodieTableConfig.BASE_FILE_FORMAT`
+   - `META_SYNC_PARTITION_FIELDS` -> `org.apache.hudi.common.table.HoodieTableConfig.PARTITION_FIELDS`
+   - `META_SYNC_ASSUME_DATE_PARTITION` -> `org.apache.hudi.common.config.HoodieMetadataConfig.ASSUME_DATE_PARTITIONING`
+   - `META_SYNC_DECODE_PARTITION` -> `org.apache.hudi.common.table.HoodieTableConfig.URL_ENCODE_PARTITIONING`
+   - `META_SYNC_USE_FILE_LISTING_FROM_METADATA` -> `org.apache.hudi.common.config.HoodieMetadataConfig.ENABLE`
+
+## Rollout/Adoption Plan
+
+- Users who set `USE_JDBC` will need to change to set `SYNC_MODE=jdbc`
+- Users who set `--enable-hive-sync` or `HIVE_SYNC_ENABLED` will need to drop the argument or config and change to `--enable-sync` or `SYNC_ENABLED`.
+- Users who import from `DataSourceOptions` for meta sync constants will need to import relevant configs from `HoodieSyncConfig` and subclasses.
+- Users who set `AwsGlueCatalogSyncTool` as sync tool class need to update the class name to `AWSGlueCatalogSyncTool`
+
+## Test Plan
+
+- CI covers most operations for Hive sync with HMS
+- end-to-end testing with setup for Glue Catalog, BigQuery, DataHub instance
+- manual testing with partitions added and removed