request.reusedSocket

• <boolean> 请求是否通过重用的套接字发送。

当通过启用保持活动的代理发送请求时，可能会重用底层套接字。 但是如果服务器在不幸的时间关闭连接，客户端可能会遇到 'ECONNRESET' 错误。

const http = require('http');

// 服务器默认有 5 秒保持活动超时
http
  .createServer((req, res) => {
    res.write('hello\n');
    res.end();
  })
  .listen(3000);

setInterval(() => {
  // 调整保持活动代理
  http.get('http://localhost:3000', { agent }, (res) => {
    res.on('data', (data) => {
      // 什么都不做
    });
  });
}, 5000); // 以 5 秒的间隔发送请求，因此很容易达到空闲超时

通过标记请求是否重用套接字，可以基于它进行自动错误重试。

const http = require('http');
const agent = new http.Agent({ keepAlive: true });

function retriableRequest() {
  const req = http
    .get('http://localhost:3000', { agent }, (res) => {
      // ...
    })
    .on('error', (err) => {
      // 检查是否需要重试
      if (req.reusedSocket && err.code === 'ECONNRESET') {
        retriableRequest();
      }
    });
}

retriableRequest();

• <boolean> Whether the request is send through a reused socket.

When sending request through a keep-alive enabled agent, the underlying socket might be reused. But if server closes connection at unfortunate time, client may run into a 'ECONNRESET' error.

const http = require('http');

// Server has a 5 seconds keep-alive timeout by default
http
  .createServer((req, res) => {
    res.write('hello\n');
    res.end();
  })
  .listen(3000);

setInterval(() => {
  // Adapting a keep-alive agent
  http.get('http://localhost:3000', { agent }, (res) => {
    res.on('data', (data) => {
      // Do nothing
    });
  });
}, 5000); // Sending request on 5s interval so it's easy to hit idle timeout

By marking a request whether it reused socket or not, we can do automatic error retry base on it.

const http = require('http');
const agent = new http.Agent({ keepAlive: true });

function retriableRequest() {
  const req = http
    .get('http://localhost:3000', { agent }, (res) => {
      // ...
    })
    .on('error', (err) => {
      // Check if retry is needed
      if (req.reusedSocket && err.code === 'ECONNRESET') {
        retriableRequest();
      }
    });
}

retriableRequest();