[HUDI-1190] Introduce @PublicAPIClass and @PublicAPIMethod annotations to mark public APIs (#1965)

- Maturity levels one of : evolving, stable, deprecated
- Took a pass and marked out most of the existing public API

hudi-spark/src/main/java/org/apache/hudi/HoodieDataSourceHelpers.java

@@ -33,12 +33,14 @@ import java.util.stream.Collectors;
 /**
  * List of helpers to aid, construction of instanttime for read and write operations using datasource.
  */
+@PublicAPIClass(maturity = ApiMaturityLevel.STABLE)
 public class HoodieDataSourceHelpers {
 
   /**
    * Checks if the Hoodie table has new data since given timestamp. This can be subsequently fed to an incremental
    * view read, to perform incremental processing.
    */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.STABLE)
   public static boolean hasNewCommits(FileSystem fs, String basePath, String commitTimestamp) {
     return listCommitsSince(fs, basePath, commitTimestamp).size() > 0;
   }
@@ -46,6 +48,7 @@ public class HoodieDataSourceHelpers {
   /**
    * Get a list of instant times that have occurred, from the given instant timestamp.
    */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.STABLE)
   public static List<String> listCommitsSince(FileSystem fs, String basePath, String instantTimestamp) {
     HoodieTimeline timeline = allCompletedCommitsCompactions(fs, basePath);
     return timeline.findInstantsAfter(instantTimestamp, Integer.MAX_VALUE).getInstants()
@@ -55,6 +58,7 @@ public class HoodieDataSourceHelpers {
   /**
    * Returns the last successful write operation's instant time.
    */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.STABLE)
   public static String latestCommit(FileSystem fs, String basePath) {
     HoodieTimeline timeline = allCompletedCommitsCompactions(fs, basePath);
     return timeline.lastInstant().get().getTimestamp();
@@ -64,6 +68,7 @@ public class HoodieDataSourceHelpers {
    * Obtain all the commits, compactions that have occurred on the timeline, whose instant times could be fed into the
    * datasource options.
    */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.STABLE)
   public static HoodieTimeline allCompletedCommitsCompactions(FileSystem fs, String basePath) {
     HoodieTableMetaClient metaClient = new HoodieTableMetaClient(fs.getConf(), basePath, true);
     if (metaClient.getTableType().equals(HoodieTableType.MERGE_ON_READ)) {

hudi-spark/src/main/java/org/apache/hudi/keygen/KeyGenerator.java

@@ -18,7 +18,10 @@
 
 package org.apache.hudi.keygen;
 
+import org.apache.hudi.ApiMaturityLevel;
 import org.apache.hudi.AvroConversionHelper;
+import org.apache.hudi.PublicAPIClass;
+import org.apache.hudi.PublicAPIMethod;
 import org.apache.hudi.common.config.TypedProperties;
 import org.apache.hudi.common.model.HoodieKey;
 
@@ -32,6 +35,7 @@ import java.util.List;
 /**
  * Abstract class to extend for plugging in extraction of {@link HoodieKey} from an Avro record.
  */
+@PublicAPIClass(maturity = ApiMaturityLevel.STABLE)
 public abstract class KeyGenerator implements Serializable, KeyGeneratorInterface {
 
   private static final String STRUCT_NAME = "hoodieRowTopLevelField";
@@ -47,6 +51,7 @@ public abstract class KeyGenerator implements Serializable, KeyGeneratorInterfac
   /**
    * Generate a Hoodie Key out of provided generic record.
    */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.STABLE)
   public abstract HoodieKey getKey(GenericRecord record);
 
   /**
@@ -54,6 +59,7 @@ public abstract class KeyGenerator implements Serializable, KeyGeneratorInterfac
    *
    * @return list of field names, when concatenated make up the record key.
    */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.EVOLVING)
   public List<String> getRecordKeyFieldNames() {
     throw new UnsupportedOperationException("Bootstrap not supported for key generator. "
         + "Please override this method in your custom key generator.");
@@ -64,6 +70,7 @@ public abstract class KeyGenerator implements Serializable, KeyGeneratorInterfac
    * @param row instance of {@link Row} from which record key is requested.
    * @return the record key of interest from {@link Row}.
    */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.EVOLVING)
   public String getRecordKey(Row row) {
     if (null == converterFn) {
       converterFn = AvroConversionHelper.createConverterToAvro(row.schema(), STRUCT_NAME, NAMESPACE);
@@ -77,6 +84,7 @@ public abstract class KeyGenerator implements Serializable, KeyGeneratorInterfac
    * @param row instance of {@link Row} from which partition path is requested
    * @return the partition path of interest from {@link Row}.
    */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.EVOLVING)
   public String getPartitionPath(Row row) {
     if (null == converterFn) {
       converterFn = AvroConversionHelper.createConverterToAvro(row.schema(), STRUCT_NAME, NAMESPACE);