content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF 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.apache.activemq.transport.discovery.http;
  
  import java.io.IOException;
  import java.io.PrintWriter;
  import java.util.ArrayList;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  import jakarta.servlet.ServletException;
  import jakarta.servlet.http.HttpServlet;
  import jakarta.servlet.http.HttpServletRequest;
  import jakarta.servlet.http.HttpServletResponse;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class DiscoveryRegistryServlet extends HttpServlet {
      private static final long serialVersionUID = 1L;
  
      private static final Logger LOG = LoggerFactory.getLogger(HTTPDiscoveryAgent.class);
      long maxKeepAge = 1000*60*60; // 1 hour.
      ConcurrentMap<String, ConcurrentMap<String, Long>> serviceGroups = new ConcurrentHashMap<String, ConcurrentMap<String, Long>>();
  
      @Override
      protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          String group = req.getPathInfo();
          String service = req.getHeader("service");
          LOG.debug("Registering: group="+group+", service="+service);
  
          ConcurrentMap<String, Long> services = getServiceGroup(group);
          services.put(service, System.currentTimeMillis());
      }
  
      private ConcurrentMap<String, Long> getServiceGroup(String group) {
          return serviceGroups.computeIfAbsent(group, k -> new ConcurrentHashMap<String, Long>());
      }
  
      @Override
      protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          try {
              long freshness = 1000*30;
              String p = req.getParameter("freshness");
              if( p!=null ) {
                  freshness = Long.parseLong(p);
              }
  
              String group = req.getPathInfo();
              LOG.debug("group="+group);
              ConcurrentMap<String, Long> services = getServiceGroup(group);
              PrintWriter writer = resp.getWriter();
  
              long now = System.currentTimeMillis();
              long dropTime = now-maxKeepAge;
              long minimumTime = now-freshness;
  
              ArrayList<String> dropList = new ArrayList<String>();
              for (Map.Entry<String, Long> entry : services.entrySet()) {
                  if( entry.getValue() > minimumTime ) {
                      writer.println(entry.getKey());
                  } else if( entry.getValue() < dropTime ) {
                      dropList.add(entry.getKey());
                  }
              }
  
              // We might as well get rid of the really old entries.
              for (String service : dropList) {
                  services.remove(service);
              }
  
  
          } catch (Exception e) {
              resp.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR, "Error occured: "+e);
          }
      }
  
      @Override
      protected void doDelete(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
          String group = req.getPathInfo();
          String service = req.getHeader("service");
          LOG.debug("Unregistering: group="+group+", service="+service);
  
          ConcurrentMap<String, Long> services = getServiceGroup(group);
          services.remove(service);
      }
  
  }
  