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.sessionmap.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.io.UncheckedIOException;
  import java.lang.reflect.Type;
  import java.net.MalformedURLException;
  import java.net.URI;
  import org.openqa.selenium.NoSuchSessionException;
  import org.openqa.selenium.grid.config.Config;
  import org.openqa.selenium.grid.data.Session;
  import org.openqa.selenium.grid.log.LoggingOptions;
  import org.openqa.selenium.grid.server.NetworkOptions;
  import org.openqa.selenium.grid.sessionmap.SessionMap;
  import org.openqa.selenium.grid.sessionmap.config.SessionMapOptions;
  import org.openqa.selenium.grid.web.Values;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.remote.SessionId;
  import org.openqa.selenium.remote.http.HttpClient;
  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 RemoteSessionMap extends SessionMap {
  
    private final HttpClient client;
  
    public RemoteSessionMap(Tracer tracer, HttpClient client) {
      super(tracer);
      this.client = Require.nonNull("HTTP client", client);
    }
  
    public static SessionMap create(Config config) {
      Tracer tracer = new LoggingOptions(config).getTracer();
      URI uri = new SessionMapOptions(config).getSessionMapUri();
      HttpClient.Factory clientFactory = new NetworkOptions(config).getHttpClientFactory(tracer);
  
      try {
        return new RemoteSessionMap(tracer, clientFactory.createClient(uri.toURL()));
      } catch (MalformedURLException e) {
        throw new UncheckedIOException(e);
      }
    }
  
    @Override
    public boolean isReady() {
      try {
        return client.execute(new HttpRequest(GET, "/readyz")).isSuccessful();
      } catch (RuntimeException e) {
        return false;
      }
    }
  
    @Override
    public boolean add(Session session) {
      Require.nonNull("Session", session);
  
      HttpRequest request = new HttpRequest(POST, "/se/grid/session");
      request.setContent(asJson(session));
  
      return makeRequest(request, Boolean.class);
    }
  
    @Override
    public Session get(SessionId id) {
      Require.nonNull("Session ID", id);
  
      Session session = makeRequest(new HttpRequest(GET, "/se/grid/session/" + id), Session.class);
      if (session == null) {
        throw new NoSuchSessionException("Unable to find session with ID: " + id);
      }
      return session;
    }
  
    @Override
    public URI getUri(SessionId id) throws NoSuchSessionException {
      Require.nonNull("Session ID", id);
  
      URI value = makeRequest(new HttpRequest(GET, "/se/grid/session/" + id + "/uri"), URI.class);
      if (value == null) {
        throw new NoSuchSessionException("Unable to find session with ID: " + id);
      }
      return value;
    }
  
    @Override
    public void remove(SessionId id) {
      Require.nonNull("Session ID", id);
  
      makeRequest(new HttpRequest(DELETE, "/se/grid/session/" + id), Void.class);
    }
  
    private <T> T makeRequest(HttpRequest request, Type typeOfT) {
      HttpTracing.inject(tracer, tracer.getCurrentContext(), request);
  
      HttpResponse response = client.execute(request);
      return Values.get(response, typeOfT);
    }
  }
  