HBASE-23604: Clarify AsyncRegistry usage in the code. (#957)

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

@@ -83,7 +83,7 @@ class AsyncConnectionImpl implements AsyncConnection {
 
   private final User user;
 
-  final AsyncRegistry registry;
+  final ConnectionRegistry registry;
 
   private final int rpcTimeout;
 
@@ -118,7 +118,7 @@ class AsyncConnectionImpl implements AsyncConnection {
 
   private final ClusterStatusListener clusterStatusListener;
 
-  public AsyncConnectionImpl(Configuration conf, AsyncRegistry registry, String clusterId,
+  public AsyncConnectionImpl(Configuration conf, ConnectionRegistry registry, String clusterId,
       User user) {
     this.conf = conf;
     this.user = user;
@@ -248,7 +248,7 @@ 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) {
@@ -342,7 +342,7 @@ public AsyncBufferedMutatorBuilder getBufferedMutatorBuilder(TableName tableName
   @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

@@ -36,14 +36,14 @@
 @InterfaceAudience.Private
 class AsyncMetaRegionLocator {
 
-  private final AsyncRegistry registry;
+  private final ConnectionRegistry registry;
 
   private final AtomicReference<RegionLocations> metaRegionLocations = new AtomicReference<>();
 
   private final AtomicReference<CompletableFuture<RegionLocations>> metaRelocateFuture =
     new AtomicReference<>();
 
-  AsyncMetaRegionLocator(AsyncRegistry registry) {
+  AsyncMetaRegionLocator(ConnectionRegistry registry) {
     this.registry = registry;
   }
 
@@ -58,7 +58,7 @@ 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/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/ConnectionFactory.java

@@ -281,7 +281,7 @@ public static CompletableFuture<AsyncConnection> createAsyncConnection(Configura
   public static CompletableFuture<AsyncConnection> createAsyncConnection(Configuration conf,
       final User user) {
     CompletableFuture<AsyncConnection> future = new CompletableFuture<>();
-    AsyncRegistry registry = AsyncRegistryFactory.getRegistry(conf);
+    ConnectionRegistry registry = ConnectionRegistryFactory.getRegistry(conf);
     addListener(registry.getClusterId(), (clusterId, error) -> {
       if (error != null) {
         registry.close();

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

@@ -217,7 +217,7 @@ class ConnectionImplementation implements ClusterConnection, Closeable {
   /**
    * Cluster registry of basic info such as clusterid and meta region location.
    */
-  private final AsyncRegistry registry;
+  private final ConnectionRegistry registry;
 
   private final ClientBackoffPolicy backoffPolicy;
 
@@ -303,7 +303,7 @@ class ConnectionImplementation implements ClusterConnection, Closeable {
         this.conf.get(BufferedMutator.CLASSNAME_KEY);
 
     try {
-      this.registry = AsyncRegistryFactory.getRegistry(conf);
+      this.registry = ConnectionRegistryFactory.getRegistry(conf);
       retrieveClusterId();
 
       this.rpcClient = RpcClientFactory.createClient(this.conf, this.clusterId, this.metrics);
@@ -434,7 +434,7 @@ public Admin getAdmin() throws IOException {
 
   @Override
   public Hbck getHbck() throws IOException {
-    return getHbck(get(registry.getMasterAddress()));
+    return getHbck(get(registry.getActiveMaster()));
   }
 
   @Override
@@ -811,7 +811,7 @@ private RegionLocations locateMeta(final TableName tableName,
       }
 
       // Look up from zookeeper
-      locations = get(this.registry.getMetaRegionLocation());
+      locations = get(this.registry.getMetaRegionLocations());
       if (locations != null) {
         cacheLocation(tableName, locations);
       }
@@ -1162,7 +1162,7 @@ private void isMasterRunning(MasterProtos.MasterService.BlockingInterface stub)
      */
     private MasterProtos.MasterService.BlockingInterface makeStubNoRetries()
         throws IOException, KeeperException {
-      ServerName sn = get(registry.getMasterAddress());
+      ServerName sn = get(registry.getActiveMaster());
       if (sn == null) {
         String msg = "ZooKeeper available but no active master location found";
         LOG.info(msg);
@@ -1211,7 +1211,7 @@ MasterProtos.MasterService.BlockingInterface makeStub() throws IOException {
 
   @Override
   public AdminProtos.AdminService.BlockingInterface getAdminForMaster() throws IOException {
-    return getAdmin(get(registry.getMasterAddress()));
+    return getAdmin(get(registry.getActiveMaster()));
   }
 
   @Override

hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncRegistry.java → hbase-client/src/main/java/org/apache/hadoop/hbase/client/ConnectionRegistry.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 {
+interface ConnectionRegistry 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 → hbase-client/src/main/java/org/apache/hadoop/hbase/client/ConnectionRegistryFactory.java

@@ -1,4 +1,4 @@
-/**
+/*
  * 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
@@ -18,26 +18,28 @@
 package org.apache.hadoop.hbase.client;
 
 import org.apache.hadoop.conf.Configuration;
-import org.apache.yetus.audience.InterfaceAudience;
 import org.apache.hadoop.hbase.util.ReflectionUtils;
+import org.apache.yetus.audience.InterfaceAudience;
 
 /**
- * Get instance of configured Registry.
+ * Factory class to get the instance of configured connection registry.
  */
 @InterfaceAudience.Private
-final class AsyncRegistryFactory {
+final class ConnectionRegistryFactory {
 
-  static final String REGISTRY_IMPL_CONF_KEY = "hbase.client.registry.impl";
+  static final String CLIENT_CONNECTION_REGISTRY_IMPL_CONF_KEY =
+      "hbase.client.connection.registry.impl";
 
-  private AsyncRegistryFactory() {
+  private ConnectionRegistryFactory() {
   }
 
   /**
-   * @return The cluster registry implementation to use.
+   * @return The connection registry implementation to use.
    */
-  static AsyncRegistry getRegistry(Configuration conf) {
-    Class<? extends AsyncRegistry> clazz =
-        conf.getClass(REGISTRY_IMPL_CONF_KEY, ZKAsyncRegistry.class, AsyncRegistry.class);
+  static ConnectionRegistry getRegistry(Configuration conf) {
+    Class<? extends ConnectionRegistry> clazz = conf.getClass(
+        CLIENT_CONNECTION_REGISTRY_IMPL_CONF_KEY, ZKConnectionRegistry.class,
+        ConnectionRegistry.class);
     return ReflectionUtils.newInstance(clazz, conf);
   }
 }

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

@@ -722,7 +722,7 @@ public CompletableFuture<Boolean> isTableAvailable(TableName tableName, byte[][]
   private CompletableFuture<Boolean> isTableAvailable(TableName tableName,
       Optional<byte[][]> splitKeys) {
     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<>();
@@ -882,7 +882,7 @@ 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 {
@@ -1098,8 +1098,9 @@ private CompletableFuture<List<HRegionLocation>> getTableHRegionLocations(TableN
     if (TableName.META_TABLE_NAME.equals(tableName)) {
       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) -> {
+      ConnectionRegistry registry = ConnectionRegistryFactory.getRegistry(
+          connection.getConfiguration());
+      addListener(registry.getMetaRegionLocations(), (metaRegions, err) -> {
         if (err != null) {
           future.completeExceptionally(err);
         } else if (metaRegions == null || metaRegions.isEmpty() ||
@@ -1127,7 +1128,7 @@ 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;
@@ -2358,7 +2359,7 @@ 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 {
@@ -2369,7 +2370,7 @@ 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());
@@ -2942,7 +2943,7 @@ 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 → hbase-client/src/main/java/org/apache/hadoop/hbase/client/ZKConnectionRegistry.java

@@ -50,15 +50,15 @@
  * Zookeeper based registry implementation.
  */
 @InterfaceAudience.Private
-class ZKAsyncRegistry implements AsyncRegistry {
+class ZKConnectionRegistry implements ConnectionRegistry {
 
-  private static final Logger LOG = LoggerFactory.getLogger(ZKAsyncRegistry.class);
+  private static final Logger LOG = LoggerFactory.getLogger(ZKConnectionRegistry.class);
 
   private final ReadOnlyZKClient zk;
 
   private final ZNodePaths znodePaths;
 
-  ZKAsyncRegistry(Configuration conf) {
+  ZKConnectionRegistry(Configuration conf) {
     this.znodePaths = new ZNodePaths(conf);
     this.zk = new ReadOnlyZKClient(conf);
   }
@@ -93,7 +93,7 @@ private static String getClusterId(byte[] data) throws DeserializationException
 
   @Override
   public CompletableFuture<String> getClusterId() {
-    return getAndConvert(znodePaths.clusterIdZNode, ZKAsyncRegistry::getClusterId);
+    return getAndConvert(znodePaths.clusterIdZNode, ZKConnectionRegistry::getClusterId);
   }
 
   @VisibleForTesting
@@ -144,7 +144,7 @@ private void getMetaRegionLocation(CompletableFuture<RegionLocations> future,
       int replicaId = znodePaths.getMetaReplicaIdFromZnode(metaReplicaZNode);
       String path = ZNodePaths.joinZNode(znodePaths.baseZNode, metaReplicaZNode);
       if (replicaId == DEFAULT_REPLICA_ID) {
-        addListener(getAndConvert(path, ZKAsyncRegistry::getMetaProto), (proto, error) -> {
+        addListener(getAndConvert(path, ZKConnectionRegistry::getMetaProto), (proto, error) -> {
           if (error != null) {
             future.completeExceptionally(error);
             return;
@@ -162,7 +162,7 @@ private void getMetaRegionLocation(CompletableFuture<RegionLocations> future,
           tryComplete(remaining, locs, future);
         });
       } else {
-        addListener(getAndConvert(path, ZKAsyncRegistry::getMetaProto), (proto, error) -> {
+        addListener(getAndConvert(path, ZKConnectionRegistry::getMetaProto), (proto, error) -> {
           if (future.isDone()) {
             return;
           }
@@ -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)
@@ -217,8 +217,8 @@ private static ZooKeeperProtos.Master getMasterProto(byte[] data) throws IOExcep
   }
 
   @Override
-  public CompletableFuture<ServerName> getMasterAddress() {
-    return getAndConvert(znodePaths.masterAddressZNode, ZKAsyncRegistry::getMasterProto)
+  public CompletableFuture<ServerName> getActiveMaster() {
+    return getAndConvert(znodePaths.masterAddressZNode, ZKConnectionRegistry::getMasterProto)
         .thenApply(proto -> {
           if (proto == null) {
             return null;