显式的绑定

有时，使用的域不是应该用于特定事件触发器的域。 或者，事件触发器可以在域的上下文中创建，但可以绑定到其他域。

例如，可能有一个域用于 HTTP 服务器，但也许我们希望为每个请求使用单独的域。

这可以通过显式绑定来实现。

// 为服务器创建顶层的域
const domain = require('domain');
const http = require('http');
const serverDomain = domain.create();

serverDomain.run(() => {
  // 服务器是在 serverDomain 的作用域中创建
  http.createServer((req, res) => {
    // req 和 res 也在 serverDomain 的作用域中创建，
    // 但是，我们希望每个请求都有单独的域。
    // 首先创建它，然后添加 req 和 res。
    const reqd = domain.create();
    reqd.add(req);
    reqd.add(res);
    reqd.on('error', (er) => {
      console.error('Error', er, req.url);
      try {
        res.writeHead(500);
        res.end('Error occurred, sorry.');
      } catch (er2) {
        console.error('Error sending 500', er2, req.url);
      }
    });
  }).listen(1337);
});

Sometimes, the domain in use is not the one that ought to be used for a specific event emitter. Or, the event emitter could have been created in the context of one domain, but ought to instead be bound to some other domain.

For example, there could be one domain in use for an HTTP server, but perhaps we would like to have a separate domain to use for each request.

That is possible via explicit binding.

// Create a top-level domain for the server
const domain = require('domain');
const http = require('http');
const serverDomain = domain.create();

serverDomain.run(() => {
  // Server is created in the scope of serverDomain
  http.createServer((req, res) => {
    // Req and res are also created in the scope of serverDomain
    // however, we'd prefer to have a separate domain for each request.
    // create it first thing, and add req and res to it.
    const reqd = domain.create();
    reqd.add(req);
    reqd.add(res);
    reqd.on('error', (er) => {
      console.error('Error', er, req.url);
      try {
        res.writeHead(500);
        res.end('Error occurred, sorry.');
      } catch (er2) {
        console.error('Error sending 500', er2, req.url);
      }
    });
  }).listen(1337);
});