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.ambari.server.agent;
  
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  
  import org.apache.ambari.server.HostNotRegisteredException;
  import org.apache.ambari.server.state.Host;
  
  import com.google.common.base.Preconditions;
  import com.google.inject.Singleton;
  
  @Singleton
  public class AgentSessionManager {
  
    private final ConcurrentMap<String, Host> registeredHosts = new ConcurrentHashMap<>(); // session ID -> host
    private final ConcurrentMap<Long, String> registeredSessionIds = new ConcurrentHashMap<>();
  
    public void register(String sessionId, Host host) {
      Preconditions.checkNotNull(sessionId);
      Preconditions.checkNotNull(host);
      Preconditions.checkNotNull(host.getHostId());
  
      String oldSessionId = registeredSessionIds.put(host.getHostId(), sessionId);
      if (oldSessionId != null) {
        registeredHosts.remove(oldSessionId);
      }
      registeredHosts.put(sessionId, host);
    }
  
    public boolean isRegistered(String sessionId) {
      return registeredHosts.containsKey(sessionId);
    }
  
    public Host getHost(String sessionId) throws HostNotRegisteredException {
      Preconditions.checkNotNull(sessionId);
  
      Host host = registeredHosts.get(sessionId);
      if (host != null) {
        return host;
      }
  
      throw HostNotRegisteredException.forSessionId(sessionId);
    }
  
    public String getSessionId(Long hostId) throws HostNotRegisteredException {
      Preconditions.checkNotNull(hostId);
  
      String sessionId = registeredSessionIds.get(hostId);
      if (sessionId != null) {
        return sessionId;
      }
  
      throw HostNotRegisteredException.forHostId(hostId);
    }
  
    public void unregisterByHost(Long hostId) {
      Preconditions.checkNotNull(hostId);
  
      String sessionId = registeredSessionIds.remove(hostId);
      if (sessionId != null) {
        registeredHosts.remove(sessionId);
      }
    }
  }
  