首先,明确三点:
1.http连接池不是万能的,过多的长连接会占用服务器资源,导致其他服务受阻
2.http连接池只适用于请求是经常访问同一主机(或同一个接口)的情况下
3.并发数不高的情况下资源利用率低下
那么,当你的业务符合上面3点,那么你可以考虑使用http连接池来提高服务器性能
使用http连接池的优点:
1.复用http连接,省去了tcp的3次握手和4次挥手的时间,极大降低请求响应的时间
2.自动管理tcp连接,不用人为地释放/创建连接
使用http连接池的大致流程 :
1.创建PoolingHttpClientConnectionManager实例
2.给manager设置参数
3.给manager设置重试策略
4.给manager设置连接管理策略
5.开启监控线程,及时关闭被服务器单向断开的连接
6.构建HttpClient实例
7.创建HttpPost/HttpGet实例,并设置参数
8.获取响应,做适当的处理
9.将用完的连接放回连接池
public class HttpConnectionPoolUtil {
private static Logger logger = LoggerFactory.getLogger(HttpConnectionPoolUtil.class);
private static final int CONNECT_TIMEOUT = Config.getHttpConnectTimeout();// 设置连接建立的超时时间为10s
private static final int SOCKET_TIMEOUT = Config.getHttpSocketTimeout();
private static final int MAX_CONN = Config.getHttpMaxPoolSize(); // 最大连接数
private static final int Max_PRE_ROUTE = Config.getHttpMaxPoolSize();
private static final int MAX_ROUTE = Config.getHttpMaxPoolSize();
private static CloseableHttpClient httpClient; // 发送请求的客户端单例
private static PoolingHttpClientConnectionManager manager; //连接池管理类
private static ScheduledExecutorService monitorExecutor;
private final static Object syncLock = new Object(); // 相当于线程锁,用于线程安全
/**
* 对http请求进行基本设置
* @param httpRequestBase http请求
*/
private static void setRequestConfig(HttpRequestBase httpRequestBase){
RequestConfig requestConfig = RequestConfig.custom().setConnectionRequestTimeout(CONNECT_TIMEOUT)
.setConnectTimeout(CONNECT_TIMEOUT)
.setSocketTimeout(SOCKET_TIMEOUT).build();
httpRequestBase.setConfig(requestConfig);
}
public static CloseableHttpClient getHttpClient(String url){
String hostName = url.split("/")[2];
System.out.println(hostName);
int port = 80;
if (hostName.contains(":")){
String[] args = hostName.split(":");
hostName = args[0];
port = Integer.parseInt(args[1]);
}
if (httpClient == null){
//多线程下多个线程同时调用getHttpClient容易导致重复创建httpClient对象的问题,所以加上了同步锁
synchronized (syncLock){
if (httpClient == null){
httpClient = createHttpClient(hostName, port);
//开启监控线程,对异常和空闲线程进行关闭
monitorExecutor = Executors.newScheduledThreadPool(1);
monitorExecutor.scheduleAtFixedRate(new TimerTask() {
@Override
public void run() {
//关闭异常连接
manager.closeExpiredConnections();
//关闭5s空闲的连接
manager.closeIdleConnections(Config.getHttpIdelTimeout(), TimeUnit.MILLISECONDS);
logger.info("close expired and idle for over 5s connection");
}
}, Config.getHttpMonitorInterval(), Config.getHttpMonitorInterval(), TimeUnit.MILLISECONDS);
}
}
}
return httpClient;
}
/**
* 根据host和port构建httpclient实例
* @param host 要访问的域名
* @param port 要访问的端口
* @return
*/
public static CloseableHttpClient createHttpClient(String host, int port){
ConnectionSocketFactory plainSocketFactory = PlainConnectionSocketFactory.getSocketFactory();
LayeredConnectionSocketFactory sslSocketFactory = SSLConnectionSocketFactory.getSocketFactory();
Registry<ConnectionSocketFactory> registry = RegistryBuilder.<ConnectionSocketFactory> create().register("http", plainSocketFactory)
.register("https", sslSocketFactory).build();
manager = new PoolingHttpClientConnectionManager(registry);
//设置连接参数
manager.setMaxTotal(MAX_CONN); // 最大连接数
manager.setDefaultMaxPerRoute(Max_PRE_ROUTE); // 路由最大连接数
HttpHost httpHost = new HttpHost(host, port);
manager.setMaxPerRoute(new HttpRoute(httpHost), MAX_ROUTE);
//请求失败时,进行请求重试
HttpRequestRetryHandler handler = new HttpRequestRetryHandler() {
@Override
public boolean retryRequest(IOException e, int i, HttpContext httpContext) {
if (i > 3){
//重试超过3次,放弃请求
logger.error("retry has more than 3 time, give up request");
return false;
}
if (e instanceof NoHttpResponseException){
//服务器没有响应,可能是服务器断开了连接,应该重试
logger.error("receive no response from server, retry");
return true;
}
if (e instanceof SSLHandshakeException){
// SSL握手异常
logger.error("SSL hand shake exception");
return false;
}
if (e instanceof InterruptedIOException){
//超时
logger.error("InterruptedIOException");
return false;
}
if (e instanceof UnknownHostException){
// 服务器不可达
logger.error("server host unknown");
return false;
}
if (e instanceof ConnectTimeoutException){
// 连接超时
logger.error("Connection Time out");
return false;
}
if (e instanceof SSLException){
logger.error("SSLException");
return false;
}
HttpClientContext context = HttpClientContext.adapt(httpContext);
HttpRequest request = context.getRequest();
if (!(request instanceof HttpEntityEnclosingRequest)){
//如果请求不是关闭连接的请求
return true;
}
return false;
}
};
CloseableHttpClient client = HttpClients.custom().setConnectionManager(manager).setRetryHandler(handler).build();
return client;
}
/**
* 设置post请求的参数
* @param httpPost
* @param params
*/
private static void setPostParams(HttpPost httpPost, Map<String, String> params){
List<NameValuePair> nvps = new ArrayList<NameValuePair>();
Set<String> keys = params.keySet();
for (String key: keys){
nvps.add(new BasicNameValuePair(key, params.get(key)));
}
try {
httpPost.setEntity(new UrlEncodedFormEntity(nvps, "utf-8"));
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
public static JsonObject post(String url, Map<String, String> params){
HttpPost httpPost = new HttpPost(url);
setRequestConfig(httpPost);
setPostParams(httpPost, params);
CloseableHttpResponse response = null;
InputStream in = null;
JsonObject object = null;
try {
response = getHttpClient(url).execute(httpPost, HttpClientContext.create());
HttpEntity entity = response.getEntity();
if (entity != null) {
in = entity.getContent();
String result = IOUtils.toString(in, "utf-8");
Gson gson = new Gson();
object = gson.fromJson(result, JsonObject.class);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try{
if (in != null) in.close();
if (response != null) response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return object;
}
/**
* 关闭连接池
*/
public static void closeConnectionPool(){
try {
httpClient.close();
manager.close();
monitorExecutor.shutdown();
} catch (IOException e) {
e.printStackTrace();
}
}
}
关键的地方有以下几点:
1.httpclient实例必须是单例,且该实例必须使用HttpClients.custom().setConnectionManager()来绑定一个PollingHttpClientConnectionManager,这样该client每次发送请求都会通过manager来获取连接,如果连接池中没有可用连接的话,则该会阻塞线程,直到有可用的连接
2.httpclients4.5.x版本直接调用ClosableHttpResponse.close()就能直接把连接放回连接池,而不是关闭连接,以前的版本貌似要调用其他方法才能把连接放回连接池
3.由于服务器一般不会允许无限期的长连接,所以需要开启监控线程,每隔一段时间就检测一下连接池中连接的情况,及时关闭异常连接和长时间空闲的连接,避免占用服务器资源.