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;
  
  import static org.openqa.selenium.remote.http.Contents.asJson;
  
  import com.google.common.collect.ImmutableMap;
  import java.io.UncheckedIOException;
  import java.util.Objects;
  import org.openqa.selenium.grid.data.NodeId;
  import org.openqa.selenium.remote.http.HttpHandler;
  import org.openqa.selenium.remote.http.HttpRequest;
  import org.openqa.selenium.remote.http.HttpResponse;
  
  public class DrainNode implements HttpHandler {
  
    private final Distributor distributor;
    private final NodeId nodeId;
  
    public DrainNode(Distributor distributor, NodeId nodeId) {
      this.distributor = Objects.requireNonNull(distributor);
      this.nodeId = Objects.requireNonNull(nodeId);
    }
  
    @Override
    public HttpResponse execute(HttpRequest req) throws UncheckedIOException {
      HttpResponse response = new HttpResponse();
      boolean value = distributor.drain(nodeId);
  
      if (value) {
        response.setContent(
            asJson(
                ImmutableMap.of(
                    "value", value, "message", "Node status was successfully set to draining.")));
      } else {
        response.setContent(
            asJson(
                ImmutableMap.of(
                    "value",
                    value,
                    "message",
                    "Unable to drain node. Please check the node exists by using /status. If so, try"
                        + " again.")));
      }
  
      return response;
    }
  }
  