客户端连接控制
<dubbo:reference interface="com.foo.BarService" connections="10" />
或
<dubbo:service interface="com.foo.BarService" connections="10" />
- 限制客户端服务使用连接不能超过 10 个。
- 如果 <dubbo:service> 和 <dubbo:reference> 都配了 connections,<dubbo:reference> 优先。
- 配置参数为connections。
public class DubboProtocol extends AbstractProtocol {
private ExchangeClient[] getClients(URL url) {
// whether to share connection
boolean service_share_connect = false;
// String CONNECTIONS_KEY = "connections";
int connections = url.getParameter(Constants.CONNECTIONS_KEY, 0);
// if not configured, connection is shared, otherwise, one connection for one service
if (connections == 0) {
service_share_connect = true;
connections = 1;
}
// 如果设置了最大连接数,就不走共享连接,直接创建指定个数的连接。
ExchangeClient[] clients = new ExchangeClient[connections];
for (int i = 0; i < clients.length; i++) {
if (service_share_connect) {
clients[i] = getSharedClient(url);
} else {
clients[i] = initClient(url);
}
}
return clients;
}
private ExchangeClient initClient(URL url) {
// client type setting.
String str = url.getParameter(Constants.CLIENT_KEY, url.getParameter(Constants.SERVER_KEY, Constants.DEFAULT_REMOTING_CLIENT));
url = url.addParameter(Constants.CODEC_KEY, DubboCodec.NAME);
// enable heartbeat by default
url = url.addParameterIfAbsent(Constants.HEARTBEAT_KEY, String.valueOf(Constants.DEFAULT_HEARTBEAT));
// BIO is not allowed since it has severe performance issue.
if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
throw new RpcException("Unsupported client type: " + str + "," +
" supported client type is " + StringUtils.join(ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions(), " "));
}
ExchangeClient client;
try {
// connection should be lazy
if (url.getParameter(Constants.LAZY_CONNECT_KEY, false)) {
client = new LazyConnectExchangeClient(url, requestHandler);
} else {
client = Exchangers.connect(url, requestHandler);
}
} catch (RemotingException e) {
throw new RpcException("Fail to create remoting client for service(" + url + "): " + e.getMessage(), e);
}
return client;
}
}
- 客户端的连接数控制是通过创建ExchangeClient的过程中进行控制。
- 如果设置了connections的变量,那么就只创建指定数量的的ExchangeClient对象。
服务端连接控制
<dubbo:provider protocol="dubbo" accepts="10" />
或
<dubbo:protocol name="dubbo" accepts="10" />
- 限制服务器端接受的连接不能超过 10 个。
- 配置参数为accepts。
public class NettyServer extends AbstractServer implements Server {
private Map<String, Channel> channels; // <ip:port, channel>
private ServerBootstrap bootstrap;
private io.netty.channel.Channel channel;
private EventLoopGroup bossGroup;
private EventLoopGroup workerGroup;
public NettyServer(URL url, ChannelHandler handler) throws RemotingException {
super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
}
}
public abstract class AbstractServer extends AbstractEndpoint implements Server {
protected static final String SERVER_THREAD_POOL_NAME = "DubboServerHandler";
private static final Logger logger = LoggerFactory.getLogger(AbstractServer.class);
ExecutorService executor;
private InetSocketAddress localAddress;
private InetSocketAddress bindAddress;
// 服务端连接控制
private int accepts;
private int idleTimeout = 600; //600 seconds
public void connected(Channel ch) throws RemotingException {
// If the server has entered the shutdown process, reject any new connection
if (this.isClosing() || this.isClosed()) {
logger.warn("Close new channel " + ch + ", cause: server is closing or has been closed. For example, receive a new connect request while in shutdown process.");
ch.close();
return;
}
Collection<Channel> channels = getChannels();
// 超过服务端连接控制,直接关闭连接。
if (accepts > 0 && channels.size() > accepts) {
logger.error("Close channel " + ch + ", cause: The server " + ch.getLocalAddress() + " connections greater than max config " + accepts);
ch.close();
return;
}
super.connected(ch);
}
}
- 服务端的连接控制数通过NettyServer的connected()方法在处理连接事件的时候进行判断。
- 如果连接数的数量超过了accepts的值那么就抛出异常并关闭连接数。
连接数说明
- 客户端没有配置connections,使用共享连接,以 ip+port 确定一个连接。
- 客户端配置了connections,客户端配置了两个引用(两个reference)且一个配置了connections=“2”,另一个没有配置connections,则没有配置connects的引用使用共享连接产生一个Client连接,配置connections=“2”使用独立连接,且连接数为2,则产生两个Client连接,所以一共产生三个Client连接。
参考
《Dubbo进阶二》——RPC协议之网络传输原理
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