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Print error when EventEmitters get too many listeners

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This commit is contained in:
Ryan Dahl 2010-12-31 18:32:52 -08:00
parent e1f4b3f009
commit 9da75f39d9
2 changed files with 40 additions and 1 deletions
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8
doc/api/events.markdown
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@ -61,6 +61,14 @@ Remove a listener from the listener array for the specified event.
Removes all listeners from the listener array for the specified event.
#### emitter.setMaxListeners(n)
By default EventEmitters will print a warning if more than 10 listeners are
added to it. This is a useful default which helps finding memory leaks.
Obviously not all Emitters should be limited to 10. This function allows
that to be increased. Set to zero for unlimited.
#### emitter.listeners(event)
Returns an array of listeners for the specified event. This array can be

33
lib/events.js
View File

@ -1,7 +1,18 @@
var EventEmitter = exports.EventEmitter = process.EventEmitter;
var isArray = Array.isArray;
// By default EventEmitters will print a warning if more than
// 10 listeners are added to it. This is a useful default which
// helps finding memory leaks.
//
// Obviously not all Emitters should be limited to 10. This function allows
// that to be increased. Set to zero for unlimited.
var defaultMaxListeners = 10;
EventEmitter.prototype.setMaxListeners = function(n) {
this._events.maxListeners = n;
};
EventEmitter.prototype.emit = function(type) {
// If there is no 'error' event listener then throw.
if (type === 'error') {
@ -71,6 +82,26 @@ EventEmitter.prototype.addListener = function(type, listener) {
// Optimize the case of one listener. Don't need the extra array object.
this._events[type] = listener;
} else if (isArray(this._events[type])) {
// Check for listener leak
if (!this._events[type].warned) {
var m;
if (this._events.maxListeners !== undefined) {
m = this._events.maxListeners;
} else {
m = defaultMaxListeners;
}
if (m && m > 0 && this._events[type].length > m) {
this._events[type].warned = true;
console.error('(node) warning: possible EventEmitter memory ' +
'leak detected. %d listeners added. ' +
'Use emitter.setMaxListeners() to increase limit.',
this._events[type].length);
console.trace();
}
}
// If we've already got an array, just append.
this._events[type].push(listener);
} else {