HBASE-23304: RPCs needed for client meta information lookup

This patch implements the RPCs needed for the meta information
lookup during connection init. New tests added to cover the RPC
code paths. HBASE-23305 builds on this to implement the client
side logic.

Fixed a bunch of checkstyle nits around the places the patch
touches.

Author: bharathv

hbase-client/src/main/java/org/apache/hadoop/hbase/shaded/protobuf/ProtobufUtil.java

@@ -376,7 +376,9 @@ private static IOException makeIOExceptionOfException(Throwable e) {
    * @see #toServerName(org.apache.hadoop.hbase.shaded.protobuf.generated.HBaseProtos.ServerName)
    */
   public static HBaseProtos.ServerName toServerName(final ServerName serverName) {
-    if (serverName == null) return null;
+    if (serverName == null) {
+      return null;
+    }
     HBaseProtos.ServerName.Builder builder =
       HBaseProtos.ServerName.newBuilder();
     builder.setHostName(serverName.getHostname());

hbase-protocol-shaded/src/main/protobuf/Master.proto

@@ -1200,3 +1200,47 @@ service HbckService {
   rpc FixMeta(FixMetaRequest)
     returns(FixMetaResponse);
 }
+
+/** Request and response to get the clusterID for this cluster */
+message GetClusterIdRequest {
+}
+message GetClusterIdResponse {
+  /** Not set if cluster ID could not be determined. */
+  optional string cluster_id = 1;
+}
+
+/** Request and response to get the currently active master name for this cluster */
+message GetActiveMasterRequest {
+}
+message GetActiveMasterResponse {
+  /** Not set if an active master could not be determined. */
+  optional ServerName server_name = 1;
+}
+
+/** Request and response to get the current list of meta region locations */
+message GetMetaRegionLocationsRequest {
+}
+message GetMetaRegionLocationsResponse {
+  /** Not set if meta region locations could not be determined. */
+  repeated RegionLocation meta_locations = 1;
+}
+
+/**
+ * Implements all the RPCs needed by clients to look up cluster meta information needed for connection establishment.
+ */
+service ClientMetaService {
+  /**
+   * Get Cluster ID for this cluster.
+   */
+  rpc GetClusterId(GetClusterIdRequest) returns(GetClusterIdResponse);
+
+  /**
+   * Get active master server name for this cluster.
+   */
+  rpc GetActiveMaster(GetActiveMasterRequest) returns(GetActiveMasterResponse);
+
+  /**
+   * Get current meta replicas' region locations.
+   */
+  rpc GetMetaRegionLocations(GetMetaRegionLocationsRequest) returns(GetMetaRegionLocationsResponse);
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterRpcServices.java

@@ -1,4 +1,4 @@
-/**
+/*
  *
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
@@ -19,7 +19,6 @@
 package org.apache.hadoop.hbase.master;
 
 import static org.apache.hadoop.hbase.master.MasterWalManager.META_FILTER;
-
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.net.BindException;
@@ -31,13 +30,15 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Optional;
 import java.util.Set;
 import java.util.stream.Collectors;
 import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.ClusterMetricsBuilder;
 import org.apache.hadoop.hbase.DoNotRetryIOException;
 import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.HRegionLocation;
 import org.apache.hadoop.hbase.MetaTableAccessor;
 import org.apache.hadoop.hbase.NamespaceDescriptor;
 import org.apache.hadoop.hbase.Server;
@@ -117,11 +118,9 @@
 import org.apache.zookeeper.KeeperException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-
 import org.apache.hbase.thirdparty.com.google.protobuf.RpcController;
 import org.apache.hbase.thirdparty.com.google.protobuf.ServiceException;
 import org.apache.hbase.thirdparty.com.google.protobuf.UnsafeByteOperations;
-
 import org.apache.hadoop.hbase.shaded.protobuf.ProtobufUtil;
 import org.apache.hadoop.hbase.shaded.protobuf.ResponseConverter;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.AccessControlProtos;
@@ -162,6 +161,7 @@
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.BalanceResponse;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.ClearDeadServersRequest;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.ClearDeadServersResponse;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.ClientMetaService;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.CreateNamespaceRequest;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.CreateNamespaceResponse;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.CreateTableRequest;
@@ -186,12 +186,18 @@
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.ExecProcedureResponse;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.FixMetaRequest;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.FixMetaResponse;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetActiveMasterRequest;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetActiveMasterResponse;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetClusterIdRequest;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetClusterIdResponse;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetClusterStatusRequest;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetClusterStatusResponse;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetCompletedSnapshotsRequest;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetCompletedSnapshotsResponse;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetLocksRequest;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetLocksResponse;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetMetaRegionLocationsRequest;
+import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetMetaRegionLocationsResponse;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetNamespaceDescriptorRequest;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetNamespaceDescriptorResponse;
 import org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos.GetProcedureResultRequest;
@@ -352,9 +358,10 @@
  */
 @InterfaceAudience.Private
 @SuppressWarnings("deprecation")
-public class MasterRpcServices extends RSRpcServices
-      implements MasterService.BlockingInterface, RegionServerStatusService.BlockingInterface,
-        LockService.BlockingInterface, HbckService.BlockingInterface {
+public class MasterRpcServices extends RSRpcServices implements
+    MasterService.BlockingInterface, RegionServerStatusService.BlockingInterface,
+    LockService.BlockingInterface, HbckService.BlockingInterface,
+    ClientMetaService.BlockingInterface {
   private static final Logger LOG = LoggerFactory.getLogger(MasterRpcServices.class.getName());
   private static final Logger AUDITLOG =
       LoggerFactory.getLogger("SecurityLogger."+MasterRpcServices.class.getName());
@@ -363,7 +370,7 @@ public class MasterRpcServices extends RSRpcServices
 
   /**
    * @return Subset of configuration to pass initializing regionservers: e.g.
-   * the filesystem to use and root directory to use.
+   *     the filesystem to use and root directory to use.
    */
   private RegionServerStartupResponse.Builder createConfigurationSubset() {
     RegionServerStartupResponse.Builder resp = addConfig(
@@ -489,15 +496,17 @@ boolean synchronousBalanceSwitch(final boolean b) throws IOException {
   protected List<BlockingServiceAndInterface> getServices() {
     List<BlockingServiceAndInterface> bssi = new ArrayList<>(5);
     bssi.add(new BlockingServiceAndInterface(
-      MasterService.newReflectiveBlockingService(this),
-      MasterService.BlockingInterface.class));
+        MasterService.newReflectiveBlockingService(this),
+        MasterService.BlockingInterface.class));
     bssi.add(new BlockingServiceAndInterface(
-      RegionServerStatusService.newReflectiveBlockingService(this),
-      RegionServerStatusService.BlockingInterface.class));
+        RegionServerStatusService.newReflectiveBlockingService(this),
+        RegionServerStatusService.BlockingInterface.class));
     bssi.add(new BlockingServiceAndInterface(LockService.newReflectiveBlockingService(this),
         LockService.BlockingInterface.class));
     bssi.add(new BlockingServiceAndInterface(HbckService.newReflectiveBlockingService(this),
         HbckService.BlockingInterface.class));
+    bssi.add(new BlockingServiceAndInterface(ClientMetaService.newReflectiveBlockingService(this),
+        ClientMetaService.BlockingInterface.class));
     bssi.addAll(super.getServices());
     return bssi;
   }
@@ -624,7 +633,9 @@ public AssignRegionResponse assignRegion(RpcController controller,
 
       final byte[] regionName = req.getRegion().getValue().toByteArray();
       final RegionInfo regionInfo = master.getAssignmentManager().getRegionInfo(regionName);
-      if (regionInfo == null) throw new UnknownRegionException(Bytes.toStringBinary(regionName));
+      if (regionInfo == null) {
+        throw new UnknownRegionException(Bytes.toStringBinary(regionName));
+      }
 
       final AssignRegionResponse arr = AssignRegionResponse.newBuilder().build();
       if (master.cpHost != null) {
@@ -669,7 +680,7 @@ public CreateNamespaceResponse createNamespace(RpcController controller,
 
   @Override
   public CreateTableResponse createTable(RpcController controller, CreateTableRequest req)
-  throws ServiceException {
+      throws ServiceException {
     TableDescriptor tableDescriptor = ProtobufUtil.toTableDescriptor(req.getTableSchema());
     byte [][] splitKeys = ProtobufUtil.getSplitKeysArray(req);
     try {
@@ -1063,7 +1074,7 @@ public GetSchemaAlterStatusResponse getSchemaAlterStatus(
    * Get list of TableDescriptors for requested tables.
    * @param c Unused (set to null).
    * @param req GetTableDescriptorsRequest that contains:
-   * - tableNames: requested tables, or if empty, all are requested
+   *     - tableNames: requested tables, or if empty, all are requested.
    * @return GetTableDescriptorsResponse
    * @throws ServiceException
    */
@@ -1207,9 +1218,9 @@ public IsProcedureDoneResponse isProcedureDone(RpcController controller,
   /**
    * Checks if the specified snapshot is done.
    * @return true if the snapshot is in file system ready to use,
-   *   false if the snapshot is in the process of completing
+   *     false if the snapshot is in the process of completing
    * @throws ServiceException wrapping UnknownSnapshotException if invalid snapshot, or
-   *  a wrapped HBaseSnapshotException with progress failure reason.
+   *     a wrapped HBaseSnapshotException with progress failure reason.
    */
   @Override
   public IsSnapshotDoneResponse isSnapshotDone(RpcController controller,
@@ -1451,7 +1462,9 @@ public OfflineRegionResponse offlineRegion(RpcController controller,
 
       final byte[] regionName = request.getRegion().getValue().toByteArray();
       final RegionInfo hri = master.getAssignmentManager().getRegionInfo(regionName);
-      if (hri == null) throw new UnknownRegionException(Bytes.toStringBinary(regionName));
+      if (hri == null) {
+        throw new UnknownRegionException(Bytes.toStringBinary(regionName));
+      }
 
       if (master.cpHost != null) {
         master.cpHost.preRegionOffline(hri);
@@ -2292,8 +2305,8 @@ public RegionSpaceUseReportResponse reportRegionSpaceUse(RpcController controlle
             report.getRegionSize(), now);
         }
       } else {
-        LOG.debug(
-          "Received region space usage report but HMaster is not ready to process it, skipping");
+        LOG.debug("Received region space usage report but HMaster is not ready to process it, "
+            + "skipping");
       }
       return RegionSpaceUseReportResponse.newBuilder().build();
     } catch (Exception e) {
@@ -2329,8 +2342,8 @@ public GetSpaceQuotaRegionSizesResponse getSpaceQuotaRegionSizes(
         }
         return builder.build();
       } else {
-        LOG.debug(
-          "Received space quota region size report but HMaster is not ready to process it, skipping");
+        LOG.debug("Received space quota region size report but HMaster is not ready to process it,"
+            + "skipping");
       }
       return builder.build();
     } catch (Exception e) {
@@ -2874,4 +2887,34 @@ private boolean shouldSubmitSCP(ServerName serverName) {
     return true;
   }
 
+  @Override
+  public GetClusterIdResponse getClusterId(RpcController rpcController, GetClusterIdRequest request)
+      throws ServiceException {
+    GetClusterIdResponse.Builder resp = GetClusterIdResponse.newBuilder();
+    String clusterId = master.getClusterId();
+    if (clusterId != null) {
+      resp.setClusterId(clusterId);
+    }
+    return resp.build();
+  }
+
+  @Override
+  public GetActiveMasterResponse getActiveMaster(RpcController rpcController,
+      GetActiveMasterRequest request) throws ServiceException {
+    GetActiveMasterResponse.Builder resp = GetActiveMasterResponse.newBuilder();
+    Optional<ServerName> serverName = master.getActiveMaster();
+    serverName.ifPresent(name -> resp.setServerName(ProtobufUtil.toServerName(name)));
+    return resp.build();
+  }
+
+  @Override
+  public GetMetaRegionLocationsResponse getMetaRegionLocations(RpcController rpcController,
+      GetMetaRegionLocationsRequest request) throws ServiceException {
+    GetMetaRegionLocationsResponse.Builder response = GetMetaRegionLocationsResponse.newBuilder();
+    Optional<List<HRegionLocation>> metaLocations =
+        master.getMetaRegionLocationCache().getMetaRegionLocations();
+    metaLocations.ifPresent(hRegionLocations -> hRegionLocations.forEach(
+      location -> response.addMetaLocations(ProtobufUtil.toRegionLocation(location))));
+    return response.build();
+  }
 }