java - Java中Http连接池中的连接驱逐策略

Question

我正在尝试在 java 中为 Web 服务实现 http 连接池。该服务将接收请求，然后调用其他http服务。

public final class HttpClientPool {
 private static HttpClientPool instance = null;
 private PoolingHttpClientConnectionManager manager;
 private IdleConnectionMonitorThread monitorThread;
 private final CloseableHttpClient client;

 public static HttpClientPool getInstance() {
  if (instance == null) {
   synchronized(HttpClientPool.class) {
    if (instance == null) {
     instance = new HttpClientPool();
    }
   }
  }
  return instance;
 }

 private HttpClientPool() {
  manager = new PoolingHttpClientConnectionManager();
  client = HttpClients.custom().setConnectionManager(manager).build();
  monitorThread = new IdleConnectionMonitorThread(manager);
  monitorThread.setDaemon(true);
  monitorThread.start();
 }

 public CloseableHttpClient getClient() {
  return client;
 }
}


class IdleConnectionMonitorThread extends Thread {
 private final HttpClientConnectionManager connMgr;
 private volatile boolean shutdown;

 IdleConnectionMonitorThread(HttpClientConnectionManager connMgr) {
  super();
  this.connMgr = connMgr;
 }

 @Override
 public void run() {
  try {
   while (!shutdown) {
    synchronized(this) {
     wait(5000);
     // Close expired connections
     connMgr.closeExpiredConnections();
     // Optionally, close connections
     // that have been idle longer than 30 sec
     connMgr.closeIdleConnections(60, TimeUnit.SECONDS);
    }
   }
  } catch (InterruptedException ex) {
   //
  }
 }

 void shutdown() {
  shutdown = true;
  synchronized(this) {
   notifyAll();
  }
 }
}

1. 如 Connection Management 中所述连接驱逐策略的文档，而不是使用 IdleConnectionMonitorThread 如果我使用 manager.setValidateAfterInactivity 会怎样。以上两种方法各有什么优缺点？

2. 上面的 Http 连接池实现正确吗？

Answer 1

将#setValidateAfterInactivity 设置为正值，持久连接将根据租用请求进行验证。也就是说，过时的和不可重用的连接不会自动从池中逐出，直到尝试重新使用它们为止。

运行一个专用线程，以指定的时间间隔迭代持久连接，并从池中删除过期或空闲的连接，可确保主动驱逐连接，但代价是额外的线程和稍高的池锁争用。