我得到以下警告:
(node) warning: possible EventEmitter memory leak detected. 11 listeners added. Use emitter.setMaxListeners() to increase limit.
Trace:
at EventEmitter.<anonymous> (events.js:139:15)
at EventEmitter.<anonymous> (node.js:385:29)
at Server.<anonymous> (server.js:20:17)
at Server.emit (events.js:70:17)
at HTTPParser.onIncoming (http.js:1514:12)
at HTTPParser.onHeadersComplete (http.js:102:31)
at Socket.ondata (http.js:1410:22)
at TCP.onread (net.js:354:27)
我在server.js中写了这样的代码:
http.createServer(
function (req, res) { ... }).listen(3013);
如何解决这个问题?
缺省情况下，任何单个事件最多可以注册10个侦听器。
如果这是你的代码，你可以通过:
const emitter = new EventEmitter()
emitter.setMaxListeners(100)
// or 0 to turn off the limit
emitter.setMaxListeners(0)
但如果这不是你的代码，你可以使用技巧来增加全局默认限制:
require('events').EventEmitter.prototype._maxListeners = 100;
当然，你可以关闭限制，但要小心:
// turn off limits by default (BE CAREFUL)
require('events').EventEmitter.prototype._maxListeners = 0;
顺便说一句。代码应该在应用程序的最开始。
ADD:从节点0.11开始，这段代码也可以改变默认限制:
require('events').EventEmitter.defaultMaxListeners = 0
You said you are using process.on('uncaughtException', callback);
Where are you executing this statement? Is it within the callback passed to http.createServer?If yes, different copy of the same callback will get attached to the uncaughtException event upon each new request, because the function (req, res) { ... } gets executed everytime a new request comes in and so will the statement process.on('uncaughtException', callback);Note that the process object is global to all your requests and adding listeners to its event everytime a new request comes in will not make any sense. You might not want such kind of behaviour. In case you want to attach a new listener for each new request, you should remove all previous listeners attached to the event as they no longer would be required using: process.removeAllListeners('uncaughtException');
感谢RLaaa给了我一个如何解决警告的真正问题/根本原因的想法。在我的例子中，是MySQL有bug的代码。
假设你写了一个承诺，里面的代码是这样的:
pool.getConnection((err, conn) => {
if(err) reject(err)
const q = 'SELECT * from `a_table`'
conn.query(q, [], (err, rows) => {
conn.release()
if(err) reject(err)
// do something
})
conn.on('error', (err) => {
reject(err)
})
})
注意，代码中有一个conn.on('error')侦听器。代码一遍又一遍地添加监听器取决于调用查询的次数。
同时if(err) reject(err)做同样的事情。
所以我删除了conn.on('error')监听器，瞧…解决了!
希望这对你有所帮助。
