HBASE-23604: Cleanup AsyncRegistry interface

Cleans up the method names to make more sense and adds a little
more javadocs for context. In future patches we can revisit
the name of the actual class to make it more self explanatory.

Author: bharathv

hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncConnectionImpl.java

@@ -257,7 +257,7 @@ AdminService.Interface getAdminStub(ServerName serverName) throws IOException {
   CompletableFuture<MasterService.Interface> getMasterStub() {
     return ConnectionUtils.getOrFetch(masterStub, masterStubMakeFuture, false, () -> {
       CompletableFuture<MasterService.Interface> future = new CompletableFuture<>();
-      addListener(registry.getMasterAddress(), (addr, error) -> {
+      addListener(registry.getActiveMaster(), (addr, error) -> {
         if (error != null) {
           future.completeExceptionally(error);
         } else if (addr == null) {
@@ -368,7 +368,7 @@ public Connection toConnection() {
   @Override
   public CompletableFuture<Hbck> getHbck() {
     CompletableFuture<Hbck> future = new CompletableFuture<>();
-    addListener(registry.getMasterAddress(), (sn, error) -> {
+    addListener(registry.getActiveMaster(), (sn, error) -> {
       if (error != null) {
         future.completeExceptionally(error);
       } else {

hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncMetaRegionLocator.java

@@ -60,7 +60,7 @@ class AsyncMetaRegionLocator {
    */
   CompletableFuture<RegionLocations> getRegionLocations(int replicaId, boolean reload) {
     return ConnectionUtils.getOrFetch(metaRegionLocations, metaRelocateFuture, reload,
-      registry::getMetaRegionLocation, locs -> isGood(locs, replicaId), "meta region location");
+      registry::getMetaRegionLocations, locs -> isGood(locs, replicaId), "meta region location");
   }
 
   private HRegionLocation getCacheLocation(HRegionLocation loc) {

hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncRegistry.java

@@ -24,16 +24,17 @@
 import org.apache.yetus.audience.InterfaceAudience;
 
 /**
- * Implementations hold cluster information such as this cluster's id, location of hbase:meta, etc..
+ * Registry for meta information needed for connection setup to a HBase cluster. Implementations
+ * hold cluster information such as this cluster's id, location of hbase:meta, etc..
  * Internal use only.
  */
 @InterfaceAudience.Private
 interface AsyncRegistry extends Closeable {
 
   /**
-   * Get the location of meta region.
+   * Get the location of meta region(s).
    */
-  CompletableFuture<RegionLocations> getMetaRegionLocation();
+  CompletableFuture<RegionLocations> getMetaRegionLocations();
 
   /**
    * Should only be called once.
@@ -43,9 +44,9 @@ interface AsyncRegistry extends Closeable {
   CompletableFuture<String> getClusterId();
 
   /**
-   * Get the address of HMaster.
+   * Get the address of active HMaster.
    */
-  CompletableFuture<ServerName> getMasterAddress();
+  CompletableFuture<ServerName> getActiveMaster();
 
   /**
    * Closes this instance and releases any system resources associated with it

hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncRegistryFactory.java

@@ -22,12 +22,12 @@
 import org.apache.hadoop.hbase.util.ReflectionUtils;
 
 /**
- * Get instance of configured Registry.
+ * Factory class to get the instance of configured registry.
  */
 @InterfaceAudience.Private
 final class AsyncRegistryFactory {
 
-  static final String REGISTRY_IMPL_CONF_KEY = "hbase.client.registry.impl";
+  static final String CLIENT_REGISTRY_IMPL_CONF_KEY = "hbase.client.registry.impl";
 
   private AsyncRegistryFactory() {
   }
@@ -37,7 +37,7 @@ private AsyncRegistryFactory() {
    */
   static AsyncRegistry getRegistry(Configuration conf) {
     Class<? extends AsyncRegistry> clazz =
-        conf.getClass(REGISTRY_IMPL_CONF_KEY, ZKAsyncRegistry.class, AsyncRegistry.class);
+        conf.getClass(CLIENT_REGISTRY_IMPL_CONF_KEY, ZKAsyncRegistry.class, AsyncRegistry.class);
     return ReflectionUtils.newInstance(clazz, conf);
   }
 }

hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncTableRegionLocatorImpl.java

@@ -55,7 +55,7 @@ public CompletableFuture<HRegionLocation> getRegionLocation(byte[] row, int repl
   @Override
   public CompletableFuture<List<HRegionLocation>> getAllRegionLocations() {
     if (TableName.isMetaTableName(tableName)) {
-      return conn.registry.getMetaRegionLocation()
+      return conn.registry.getMetaRegionLocations()
         .thenApply(locs -> Arrays.asList(locs.getRegionLocations()));
     }
     return AsyncMetaTableAccessor.getTableHRegionLocations(conn.getTable(TableName.META_TABLE_NAME),

hbase-client/src/main/java/org/apache/hadoop/hbase/client/RawAsyncHBaseAdmin.java

@@ -709,7 +709,7 @@ public CompletableFuture<Boolean> isTableDisabled(TableName tableName) {
   @Override
   public CompletableFuture<Boolean> isTableAvailable(TableName tableName) {
     if (TableName.isMetaTableName(tableName)) {
-      return connection.registry.getMetaRegionLocation().thenApply(locs -> Stream
+      return connection.registry.getMetaRegionLocations().thenApply(locs -> Stream
         .of(locs.getRegionLocations()).allMatch(loc -> loc != null && loc.getServerName() != null));
     }
     CompletableFuture<Boolean> future = new CompletableFuture<>();
@@ -847,7 +847,7 @@ public CompletableFuture<List<RegionInfo>> getRegions(ServerName serverName) {
   @Override
   public CompletableFuture<List<RegionInfo>> getRegions(TableName tableName) {
     if (tableName.equals(META_TABLE_NAME)) {
-      return connection.registry.getMetaRegionLocation()
+      return connection.registry.getMetaRegionLocations()
         .thenApply(locs -> Stream.of(locs.getRegionLocations()).map(HRegionLocation::getRegion)
           .collect(Collectors.toList()));
     } else {
@@ -1076,7 +1076,7 @@ private CompletableFuture<List<HRegionLocation>> getTableHRegionLocations(TableN
       CompletableFuture<List<HRegionLocation>> future = new CompletableFuture<>();
       // For meta table, we use zk to fetch all locations.
       AsyncRegistry registry = AsyncRegistryFactory.getRegistry(connection.getConfiguration());
-      addListener(registry.getMetaRegionLocation(), (metaRegions, err) -> {
+      addListener(registry.getMetaRegionLocations(), (metaRegions, err) -> {
         if (err != null) {
           future.completeExceptionally(err);
         } else if (metaRegions == null || metaRegions.isEmpty() ||
@@ -1104,7 +1104,7 @@ private CompletableFuture<Void> compact(TableName tableName, byte[] columnFamily
 
     switch (compactType) {
       case MOB:
-        addListener(connection.registry.getMasterAddress(), (serverName, err) -> {
+        addListener(connection.registry.getActiveMaster(), (serverName, err) -> {
           if (err != null) {
             future.completeExceptionally(err);
             return;
@@ -2347,7 +2347,7 @@ CompletableFuture<HRegionLocation> getRegionLocation(byte[] regionNameOrEncodedR
         String encodedName = Bytes.toString(regionNameOrEncodedRegionName);
         if (encodedName.length() < RegionInfo.MD5_HEX_LENGTH) {
           // old format encodedName, should be meta region
-          future = connection.registry.getMetaRegionLocation()
+          future = connection.registry.getMetaRegionLocations()
             .thenApply(locs -> Stream.of(locs.getRegionLocations())
               .filter(loc -> loc.getRegion().getEncodedName().equals(encodedName)).findFirst());
         } else {
@@ -2358,7 +2358,7 @@ CompletableFuture<HRegionLocation> getRegionLocation(byte[] regionNameOrEncodedR
         RegionInfo regionInfo =
           MetaTableAccessor.parseRegionInfoFromRegionName(regionNameOrEncodedRegionName);
         if (regionInfo.isMetaRegion()) {
-          future = connection.registry.getMetaRegionLocation()
+          future = connection.registry.getMetaRegionLocations()
             .thenApply(locs -> Stream.of(locs.getRegionLocations())
               .filter(loc -> loc.getRegion().getReplicaId() == regionInfo.getReplicaId())
               .findFirst());
@@ -2931,7 +2931,7 @@ public CompletableFuture<CompactionState> getCompactionState(TableName tableName
 
     switch (compactType) {
       case MOB:
-        addListener(connection.registry.getMasterAddress(), (serverName, err) -> {
+        addListener(connection.registry.getActiveMaster(), (serverName, err) -> {
           if (err != null) {
             future.completeExceptionally(err);
             return;

hbase-client/src/main/java/org/apache/hadoop/hbase/client/ZKAsyncRegistry.java

@@ -191,7 +191,7 @@ private void getMetaRegionLocation(CompletableFuture<RegionLocations> future,
   }
 
   @Override
-  public CompletableFuture<RegionLocations> getMetaRegionLocation() {
+  public CompletableFuture<RegionLocations> getMetaRegionLocations() {
     CompletableFuture<RegionLocations> future = new CompletableFuture<>();
     addListener(
       zk.list(znodePaths.baseZNode)
@@ -217,7 +217,7 @@ private static ZooKeeperProtos.Master getMasterProto(byte[] data) throws IOExcep
   }
 
   @Override
-  public CompletableFuture<ServerName> getMasterAddress() {
+  public CompletableFuture<ServerName> getActiveMaster() {
     return getAndConvert(znodePaths.masterAddressZNode, ZKAsyncRegistry::getMasterProto)
         .thenApply(proto -> {
           if (proto == null) {

hbase-client/src/test/java/org/apache/hadoop/hbase/client/DoNothingAsyncRegistry.java

@@ -33,7 +33,7 @@ public DoNothingAsyncRegistry(Configuration conf) {
   }
 
   @Override
-  public CompletableFuture<RegionLocations> getMetaRegionLocation() {
+  public CompletableFuture<RegionLocations> getMetaRegionLocations() {
     return CompletableFuture.completedFuture(null);
   }
 
@@ -43,7 +43,7 @@ public CompletableFuture<String> getClusterId() {
   }
 
   @Override
-  public CompletableFuture<ServerName> getMasterAddress() {
+  public CompletableFuture<ServerName> getActiveMaster() {
     return CompletableFuture.completedFuture(null);
   }
 

hbase-client/src/test/java/org/apache/hadoop/hbase/client/TestAsyncMetaRegionLocatorFailFast.java

@@ -50,7 +50,7 @@ public FaultyAsyncRegistry(Configuration conf) {
     }
 
     @Override
-    public CompletableFuture<RegionLocations> getMetaRegionLocation() {
+    public CompletableFuture<RegionLocations> getMetaRegionLocations() {
       return FutureUtils.failedFuture(new DoNotRetryRegionException("inject error"));
     }
   }

hbase-client/src/test/java/org/apache/hadoop/hbase/client/TestAsyncRegistryLeak.java

@@ -70,7 +70,7 @@ public void close() {
 
   @BeforeClass
   public static void setUp() {
-    CONF.setClass(AsyncRegistryFactory.REGISTRY_IMPL_CONF_KEY, AsyncRegistryForTest.class,
+    CONF.setClass(AsyncRegistryFactory.CLIENT_REGISTRY_IMPL_CONF_KEY, AsyncRegistryForTest.class,
       AsyncRegistry.class);
   }
 

hbase-server/src/test/java/org/apache/hadoop/hbase/client/DummyAsyncRegistry.java

@@ -27,10 +27,10 @@
  */
 public class DummyAsyncRegistry implements AsyncRegistry {
 
-  public static final String REGISTRY_IMPL_CONF_KEY = AsyncRegistryFactory.REGISTRY_IMPL_CONF_KEY;
+  public static final String REGISTRY_IMPL_CONF_KEY = AsyncRegistryFactory.CLIENT_REGISTRY_IMPL_CONF_KEY;
 
   @Override
-  public CompletableFuture<RegionLocations> getMetaRegionLocation() {
+  public CompletableFuture<RegionLocations> getMetaRegionLocations() {
     return null;
   }
 
@@ -40,7 +40,7 @@ public CompletableFuture<String> getClusterId() {
   }
 
   @Override
-  public CompletableFuture<ServerName> getMasterAddress() {
+  public CompletableFuture<ServerName> getActiveMaster() {
     return null;
   }
 

hbase-server/src/test/java/org/apache/hadoop/hbase/client/RegionReplicaTestHelper.java

@@ -50,7 +50,7 @@ public String explainFailure() throws IOException {
         @Override
         public boolean evaluate() throws IOException {
           try {
-            RegionLocations locs = registry.getMetaRegionLocation().get();
+            RegionLocations locs = registry.getMetaRegionLocations().get();
             if (locs.size() < regionReplication) {
               return false;
             }

hbase-server/src/test/java/org/apache/hadoop/hbase/client/TestZKAsyncRegistry.java

@@ -84,10 +84,10 @@ public void test() throws InterruptedException, ExecutionException, IOException
     assertEquals("Expected " + expectedClusterId + ", found=" + clusterId, expectedClusterId,
       clusterId);
     assertEquals(TEST_UTIL.getHBaseCluster().getMaster().getServerName(),
-      REGISTRY.getMasterAddress().get());
+      REGISTRY.getActiveMaster().get());
     RegionReplicaTestHelper
       .waitUntilAllMetaReplicasHavingRegionLocation(TEST_UTIL.getConfiguration(), REGISTRY, 3);
-    RegionLocations locs = REGISTRY.getMetaRegionLocation().get();
+    RegionLocations locs = REGISTRY.getMetaRegionLocations().get();
     assertEquals(3, locs.getRegionLocations().length);
     IntStream.range(0, 3).forEach(i -> {
       HRegionLocation loc = locs.getRegionLocation(i);
@@ -121,7 +121,7 @@ public void testNoMetaAvailable() throws InterruptedException {
     conf.set("zookeeper.znode.metaserver", "whatever");
     try (ZKAsyncRegistry registry = new ZKAsyncRegistry(conf)) {
       try {
-        registry.getMetaRegionLocation().get();
+        registry.getMetaRegionLocations().get();
         fail("Should have failed since we set an incorrect meta znode prefix");
       } catch (ExecutionException e) {
         assertThat(e.getCause(), instanceOf(IOException.class));