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.web;
  
  import static java.net.HttpURLConnection.HTTP_INTERNAL_ERROR;
  import static java.net.HttpURLConnection.HTTP_NO_CONTENT;
  import static java.util.logging.Level.WARNING;
  import static org.openqa.selenium.json.Json.MAP_TYPE;
  
  import com.google.common.net.MediaType;
  import java.io.UncheckedIOException;
  import java.util.Map;
  import java.util.logging.Logger;
  import org.openqa.selenium.internal.Require;
  import org.openqa.selenium.json.Json;
  import org.openqa.selenium.remote.http.Contents;
  import org.openqa.selenium.remote.http.HttpHandler;
  import org.openqa.selenium.remote.http.HttpMethod;
  import org.openqa.selenium.remote.http.HttpRequest;
  import org.openqa.selenium.remote.http.HttpResponse;
  
  /**
   * An {@link HttpHandler} that obeys the contracted required by a Kubernetes health check, but which
   * reads a selenium `/status` endpoint.
   */
  public class StatusBasedReadinessCheck implements HttpHandler {
  
    private static final Logger LOG = Logger.getLogger(StatusBasedReadinessCheck.class.getName());
    private static final Json JSON = new Json();
    private final HttpHandler handler;
    private final HttpMethod method;
    private final String url;
  
    public StatusBasedReadinessCheck(HttpHandler handler, HttpMethod method, String url) {
      this.handler = Require.nonNull("handler", handler);
      this.method = Require.nonNull("HTTP method", method);
      this.url = Require.nonNull("URL for status", url);
    }
  
    @Override
    public HttpResponse execute(HttpRequest req) throws UncheckedIOException {
      try {
        HttpResponse response = handler.execute(new HttpRequest(method, url));
        Map<String, Object> valueWrapped = JSON.toType(Contents.string(response), MAP_TYPE);
  
        Object value = valueWrapped.get("value");
        if (value instanceof Map) {
          Object ready = ((Map<?, ?>) value).get("ready");
          if (Boolean.TRUE.equals(ready)) {
            return new HttpResponse().setStatus(HTTP_NO_CONTENT);
          }
        }
  
        return new HttpResponse()
            .setStatus(HTTP_INTERNAL_ERROR)
            .setHeader("Content-Type", MediaType.PLAIN_TEXT_UTF_8.toString())
            .setContent(
                Contents.utf8String("Unable to determine status of server from " + valueWrapped));
      } catch (Exception e) {
        LOG.log(WARNING, "Unable to read status", e);
        return new HttpResponse()
            .setStatus(HTTP_INTERNAL_ERROR)
            .setHeader("Content-Type", MediaType.PLAIN_TEXT_UTF_8.toString())
            .setContent(Contents.utf8String("Unable to determine status of server"));
      }
    }
  }
  