code: // Licensed to the Software Freedom Conservancy (SFC) under one
  // or more contributor license agreements.  See the NOTICE file
  // distributed with this work for additional information
  // regarding copyright ownership.  The SFC licenses this file
  // to you under the Apache License, Version 2.0 (the
  // "License"); you may not use this file except in compliance
  // with the License.  You may obtain a copy of the License at
  //
  //   http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing,
  // software distributed under the License is distributed on an
  // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  // KIND, either express or implied.  See the License for the
  // specific language governing permissions and limitations
  // under the License.
  
  package org.openqa.selenium.grid.distributor.remote;
  
  import static org.openqa.selenium.remote.http.Contents.asJson;
  import static org.openqa.selenium.remote.http.HttpMethod.DELETE;
  import static org.openqa.selenium.remote.http.HttpMethod.GET;
  import static org.openqa.selenium.remote.http.HttpMethod.POST;
  
  import java.net.URL;
  import java.util.logging.Logger;
  import org.openqa.selenium.SessionNotCreatedException;
  import org.openqa.selenium.grid.data.CreateSessionResponse;
  import org.openqa.selenium.grid.data.DistributorStatus;
  import org.openqa.selenium.grid.data.NodeId;
  import org.openqa.selenium.grid.data.SessionRequest;
  import org.openqa.selenium.grid.distributor.Distributor;
  import org.openqa.selenium.grid.node.Node;
  import org.openqa.selenium.grid.security.AddSecretFilter;
  import org.openqa.selenium.grid.security.Secret;
  import org.openqa.selenium.grid.web.Values;
  import org.openqa.selenium.internal.Either;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.remote.http.Filter;
  import org.openqa.selenium.remote.http.HttpClient;
  import org.openqa.selenium.remote.http.HttpHandler;
  import org.openqa.selenium.remote.http.HttpRequest;
  import org.openqa.selenium.remote.http.HttpResponse;
  import org.openqa.selenium.remote.tracing.HttpTracing;
  import org.openqa.selenium.remote.tracing.Tracer;
  
  public class RemoteDistributor extends Distributor {
  
    private static final Logger LOG = Logger.getLogger("Selenium Distributor (Remote)");
    private final HttpHandler client;
    private final Filter addSecret;
  
    public RemoteDistributor(
        Tracer tracer, HttpClient.Factory factory, URL url, Secret registrationSecret) {
      super(tracer, factory, registrationSecret);
      this.client = factory.createClient(url);
  
      this.addSecret = new AddSecretFilter(registrationSecret);
    }
  
    @Override
    public boolean isReady() {
      try {
        return client.execute(new HttpRequest(GET, "/readyz")).isSuccessful();
      } catch (Exception e) {
        return false;
      }
    }
  
    @Override
    public RemoteDistributor add(Node node) {
      HttpRequest request = new HttpRequest(POST, "/se/grid/distributor/node");
      HttpTracing.inject(tracer, tracer.getCurrentContext(), request);
      request.setContent(asJson(node.getStatus()));
  
      HttpResponse response = client.with(addSecret).execute(request);
  
      Values.get(response, Void.class);
  
      LOG.info(String.format("Added node %s.", node.getId()));
  
      return this;
    }
  
    @Override
    public boolean drain(NodeId nodeId) {
      Require.nonNull("Node ID", nodeId);
      HttpRequest request = new HttpRequest(POST, "/se/grid/distributor/node/" + nodeId + "/drain");
      HttpTracing.inject(tracer, tracer.getCurrentContext(), request);
      request.setContent(asJson(nodeId));
  
      HttpResponse response = client.with(addSecret).execute(request);
  
      return Values.get(response, Boolean.class);
    }
  
    @Override
    public void remove(NodeId nodeId) {
      Require.nonNull("Node ID", nodeId);
      HttpRequest request = new HttpRequest(DELETE, "/se/grid/distributor/node/" + nodeId);
      HttpTracing.inject(tracer, tracer.getCurrentContext(), request);
  
      HttpResponse response = client.with(addSecret).execute(request);
  
      Values.get(response, Void.class);
    }
  
    @Override
    public DistributorStatus getStatus() {
      HttpRequest request = new HttpRequest(GET, "/se/grid/distributor/status");
      HttpTracing.inject(tracer, tracer.getCurrentContext(), request);
  
      HttpResponse response = client.execute(request);
  
      return Values.get(response, DistributorStatus.class);
    }
  
    @Override
    public Either<SessionNotCreatedException, CreateSessionResponse> newSession(
        SessionRequest sessionRequest) throws SessionNotCreatedException {
      HttpRequest req =
          new HttpRequest(POST, "/se/grid/distributor/session").setContent(asJson(sessionRequest));
      HttpTracing.inject(tracer, tracer.getCurrentContext(), req);
  
      HttpResponse res = client.execute(req);
  
      if (res.isSuccessful()) {
        return Either.right(Values.get(res, CreateSessionResponse.class));
      } else {
        return Either.left(Values.get(res, SessionNotCreatedException.class));
      }
    }
  }
  