/**
    * 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.hadoop.hbase.ipc;
  
  import java.util.Iterator;
  import java.util.LinkedList;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.net.Address;
  import org.apache.hadoop.hbase.util.EnvironmentEdgeManager;
  import org.apache.hadoop.hbase.util.Pair;
  
  /**
   * A class to manage a list of servers that failed recently.
   */
  @InterfaceAudience.Private
  public class FailedServers {
    private final LinkedList<Pair<Long, Address>> failedServers = new
        LinkedList<Pair<Long, Address>>();
    private final int recheckServersTimeout;
    private static final Log LOG = LogFactory.getLog(FailedServers.class);
  
    public FailedServers(Configuration conf) {
      this.recheckServersTimeout = conf.getInt(
          RpcClient.FAILED_SERVER_EXPIRY_KEY, RpcClient.FAILED_SERVER_EXPIRY_DEFAULT);
    }
  
    /**
     * Add an address to the list of the failed servers list.
     */
    public synchronized void addToFailedServers(Address address, Throwable throwable) {
      final long expiry = EnvironmentEdgeManager.currentTime() + recheckServersTimeout;
      failedServers.addFirst(new Pair<Long, Address>(expiry, address));
      if (LOG.isDebugEnabled()) {
        LOG.debug(
          "Added failed server with address " + address + " to list caused by "
              + throwable.toString());
      }
    }
  
    /**
     * Check if the server should be considered as bad. Clean the old entries of the list.
     *
     * @return true if the server is in the failed servers list
     */
    public synchronized boolean isFailedServer(final Address address) {
      if (failedServers.isEmpty()) {
        return false;
      }
  
      final long now = EnvironmentEdgeManager.currentTime();
  
      // iterate, looking for the search entry and cleaning expired entries
      Iterator<Pair<Long, Address>> it = failedServers.iterator();
      while (it.hasNext()) {
        Pair<Long, Address> cur = it.next();
        if (cur.getFirst() < now) {
          it.remove();
        } else {
          if (address.equals(cur.getSecond())) {
            return true;
          }
        }
      }
  
      return false;
    }
  }