services: add support for channelz.GetServer()

api/src/main/java/io/grpc/InternalChannelz.java

@@ -179,6 +179,12 @@ public final class InternalChannelz {
     return new ServerList(serverList, !iterator.hasNext());
   }
 
+  /** Returns a server. */
+  @Nullable
+  public InternalInstrumented<ServerStats> getServer(long id) {
+    return servers.get(id);
+  }
+
   /** Returns socket refs for a server. */
   @Nullable
   public ServerSocketsList getServerSockets(long serverId, long fromId, int maxPageSize) {

services/src/main/java/io/grpc/services/ChannelzService.java

@@ -22,6 +22,7 @@ import io.grpc.InternalChannelz;
 import io.grpc.InternalChannelz.ChannelStats;
 import io.grpc.InternalChannelz.ServerList;
 import io.grpc.InternalChannelz.ServerSocketsList;
+import io.grpc.InternalChannelz.ServerStats;
 import io.grpc.InternalChannelz.SocketStats;
 import io.grpc.InternalInstrumented;
 import io.grpc.Status;
@@ -29,6 +30,8 @@ import io.grpc.StatusRuntimeException;
 import io.grpc.channelz.v1.ChannelzGrpc;
 import io.grpc.channelz.v1.GetChannelRequest;
 import io.grpc.channelz.v1.GetChannelResponse;
+import io.grpc.channelz.v1.GetServerRequest;
+import io.grpc.channelz.v1.GetServerResponse;
 import io.grpc.channelz.v1.GetServerSocketsRequest;
 import io.grpc.channelz.v1.GetServerSocketsResponse;
 import io.grpc.channelz.v1.GetServersRequest;
@@ -126,6 +129,33 @@ public final class ChannelzService extends ChannelzGrpc.ChannelzImplBase {
     responseObserver.onCompleted();
   }
 
+  /** Returns a server. */
+  @Override
+  public void getServer(
+      GetServerRequest request, StreamObserver<GetServerResponse> responseObserver) {
+    InternalInstrumented<ServerStats> s = channelz.getServer(request.getServerId());
+    if (s == null) {
+      responseObserver.onError(
+          Status.NOT_FOUND.withDescription("Can't find server " + request.getServerId())
+              .asRuntimeException());
+      return;
+    }
+
+    GetServerResponse resp;
+    try {
+      resp = GetServerResponse
+          .newBuilder()
+          .setServer(ChannelzProtoUtil.toServer(s))
+          .build();
+    } catch (StatusRuntimeException e) {
+      responseObserver.onError(e);
+      return;
+    }
+
+    responseObserver.onNext(resp);
+    responseObserver.onCompleted();
+  }
+
   /** Returns a subchannel. */
   @Override
   public void getSubchannel(

services/src/test/java/io/grpc/services/ChannelzServiceTest.java

@@ -25,6 +25,8 @@ import io.grpc.InternalChannelz;
 import io.grpc.Status;
 import io.grpc.channelz.v1.GetChannelRequest;
 import io.grpc.channelz.v1.GetChannelResponse;
+import io.grpc.channelz.v1.GetServerRequest;
+import io.grpc.channelz.v1.GetServerResponse;
 import io.grpc.channelz.v1.GetServersRequest;
 import io.grpc.channelz.v1.GetServersResponse;
 import io.grpc.channelz.v1.GetSocketRequest;
@@ -127,6 +129,24 @@ public class ChannelzServiceTest {
         getServersHelper(0));
   }
 
+  @Test
+  public void getServer() throws ExecutionException, InterruptedException {
+    TestServer server = new TestServer();
+    assertServerNotFound(server.getLogId().getId());
+
+    channelz.addServer(server);
+    assertEquals(
+        GetServerResponse
+            .newBuilder()
+            .setServer(ChannelzProtoUtil.toServer(server))
+            .build(),
+        getServerHelper(server.getLogId().getId()));
+
+    channelz.removeServer(server);
+    assertServerNotFound(server.getLogId().getId());
+  }
+
+
   @Test
   public void getSocket() throws Exception {
     TestSocket socket = new TestSocket();
@@ -212,6 +232,26 @@ public class ChannelzServiceTest {
     return responseCaptor.getValue();
   }
 
+  private void assertServerNotFound(long id) {
+    @SuppressWarnings("unchecked")
+    StreamObserver<GetServerResponse> observer = mock(StreamObserver.class);
+    ArgumentCaptor<Exception> exceptionCaptor = ArgumentCaptor.forClass(Exception.class);
+    service.getServer(GetServerRequest.newBuilder().setServerId(id).build(), observer);
+    verify(observer).onError(exceptionCaptor.capture());
+    Status s = Status.fromThrowable(exceptionCaptor.getValue());
+    assertWithMessage(s.toString()).that(s.getCode()).isEqualTo(Status.Code.NOT_FOUND);
+  }
+
+  private GetServerResponse getServerHelper(long id) {
+    @SuppressWarnings("unchecked")
+    StreamObserver<GetServerResponse> observer = mock(StreamObserver.class);
+    ArgumentCaptor<GetServerResponse> response = ArgumentCaptor.forClass(GetServerResponse.class);
+    service.getServer(GetServerRequest.newBuilder().setServerId(id).build(), observer);
+    verify(observer).onNext(response.capture());
+    verify(observer).onCompleted();
+    return response.getValue();
+  }
+
   private void assertSocketNotFound(long id) {
     @SuppressWarnings("unchecked")
     StreamObserver<GetSocketResponse> observer = mock(StreamObserver.class);