Revert "RATIS-2325. Create GrpcStubPool for GrpcServerProtocolClient (#1283)"

This reverts commit d11604c.

Author: szetszwo

ratis-grpc/src/main/java/org/apache/ratis/grpc/GrpcConfigKeys.java

@@ -282,15 +282,6 @@ static GrpcTlsConfig tlsConf(Parameters parameters) {
     static void setTlsConf(Parameters parameters, GrpcTlsConfig conf) {
       parameters.put(TLS_CONF_PARAMETER, conf, TLS_CONF_CLASS);
     }
-
-    String STUB_POOL_SIZE_KEY = PREFIX + ".stub.pool.size";
-    int STUB_POOL_SIZE_DEFAULT = 10;
-    static int stubPoolSize(RaftProperties properties) {
-      return get(properties::getInt, STUB_POOL_SIZE_KEY, STUB_POOL_SIZE_DEFAULT, getDefaultLog());
-    }
-    static void setStubPoolSize(RaftProperties properties, int size) {
-      setInt(properties::setInt, STUB_POOL_SIZE_KEY, size);
-    }
   }
 
   String MESSAGE_SIZE_MAX_KEY = PREFIX + ".message.size.max";

ratis-grpc/src/main/java/org/apache/ratis/grpc/server/GrpcServerProtocolClient.java

@@ -45,7 +45,6 @@
 class GrpcServerProtocolClient implements Closeable {
   // Common channel
   private final ManagedChannel channel;
-  private final GrpcStubPool<RaftServerProtocolServiceStub> pool;
   // Channel and stub for heartbeat
   private ManagedChannel hbChannel;
   private RaftServerProtocolServiceStub hbAsyncStub;
@@ -58,7 +57,7 @@ class GrpcServerProtocolClient implements Closeable {
   //visible for using in log / error messages AND to use in instrumented tests
   private final RaftPeerId raftPeerId;
 
-  GrpcServerProtocolClient(RaftPeer target, int connections, int flowControlWindow,
+  GrpcServerProtocolClient(RaftPeer target, int flowControlWindow,
       TimeDuration requestTimeout, SslContext sslContext, boolean separateHBChannel) {
     raftPeerId = target.getId();
     LOG.info("Build channel for {}", target);
@@ -71,7 +70,6 @@ class GrpcServerProtocolClient implements Closeable {
       hbAsyncStub = RaftServerProtocolServiceGrpc.newStub(hbChannel);
     }
     requestTimeoutDuration = requestTimeout;
-    this.pool = new GrpcStubPool<>(target, connections, RaftServerProtocolServiceGrpc::newStub, sslContext);
   }
 
   private ManagedChannel buildChannel(RaftPeer target, int flowControlWindow, SslContext sslContext) {
@@ -96,7 +94,6 @@ public void close() {
       GrpcUtil.shutdownManagedChannel(hbChannel);
     }
     GrpcUtil.shutdownManagedChannel(channel);
-    pool.close();
   }
 
   public RequestVoteReplyProto requestVote(RequestVoteRequestProto request) {
@@ -115,36 +112,8 @@ public StartLeaderElectionReplyProto startLeaderElection(StartLeaderElectionRequ
   }
 
   void readIndex(ReadIndexRequestProto request, StreamObserver<ReadIndexReplyProto> s) {
-    GrpcStubPool.PooledStub<RaftServerProtocolServiceStub> p;
-    try {
-      p = pool.acquire();
-    } catch (InterruptedException e) {
-      Thread.currentThread().interrupt();
-      s.onError(e); return;
-    }
-    p.getStub().withDeadlineAfter(requestTimeoutDuration.getDuration(), requestTimeoutDuration.getUnit())
-            .readIndex(request, new StreamObserver<ReadIndexReplyProto>() {
-              @Override
-              public void onNext(ReadIndexReplyProto v) {
-                s.onNext(v);
-              }
-              @Override
-              public void onError(Throwable t) {
-                try {
-                  s.onError(t);
-                } finally {
-                  p.release();
-                }
-              }
-              @Override
-              public void onCompleted() {
-                try {
-                  s.onCompleted();
-                } finally {
-                  p.release();
-                }
-              }
-            });
+    asyncStub.withDeadlineAfter(requestTimeoutDuration.getDuration(), requestTimeoutDuration.getUnit())
+        .readIndex(request, s);
   }
 
   CallStreamObserver<AppendEntriesRequestProto> appendEntries(

ratis-grpc/src/main/java/org/apache/ratis/grpc/server/GrpcServicesImpl.java

@@ -108,7 +108,6 @@ public static final class Builder {
     private int serverPort;
     private SslContext serverSslContextForServer;
     private SslContext serverSslContextForClient;
-    private int serverStubPoolSize;
 
     private SizeInBytes messageSizeMax;
     private SizeInBytes flowControlWindow;
@@ -131,7 +130,6 @@ public Builder setServer(RaftServer raftServer) {
       this.flowControlWindow = GrpcConfigKeys.flowControlWindow(properties, LOG::info);
       this.requestTimeoutDuration = RaftServerConfigKeys.Rpc.requestTimeout(properties);
       this.separateHeartbeatChannel = GrpcConfigKeys.Server.heartbeatChannel(properties);
-      this.serverStubPoolSize = GrpcConfigKeys.Server.stubPoolSize(properties);
 
       final SizeInBytes appenderBufferSize = RaftServerConfigKeys.Log.Appender.bufferByteLimit(properties);
       final SizeInBytes gap = SizeInBytes.ONE_MB;
@@ -152,7 +150,7 @@ public Builder setCustomizer(Customizer customizer) {
     }
 
     private GrpcServerProtocolClient newGrpcServerProtocolClient(RaftPeer target) {
-      return new GrpcServerProtocolClient(target, serverStubPoolSize, flowControlWindow.getSizeInt(),
+      return new GrpcServerProtocolClient(target, flowControlWindow.getSizeInt(),
           requestTimeoutDuration, serverSslContextForClient, separateHeartbeatChannel);
     }