我正在评估Node.js是否可能取代我当前在Java Web应用程序上的推送功能。我编写了一个简单的长轮询服务器,它的工作方式类似于客户端和Java后端之间的中介。客户端发出订阅请求,然后Java服务器可以通过调用Node.js来通知订阅的客户端。到目前为止,它似乎运行良好,但我收到了以下消息,指出内存泄漏:
(node) warning: possible EventEmitter memory leak detected. 11 listeners added.
Use emitter.setMaxListeners() to increase limit.
Trace
at EventEmitter.addListener (events.js:168:15)
at EventEmitter.once (events.js:189:8)
at route (C:UsersJuan Pablopushserver.js:42:12)
at Server.onRequest (C:UsersJuan Pablopushserver.js:32:3)
at Server.EventEmitter.emit (events.js:91:17)
at HTTPParser.parser.onIncoming (http.js:1793:12)
at HTTPParser.parserOnHeadersComplete [as onHeadersComplete] (http.js:111:23
)
at Socket.socket.ondata (http.js:1690:22)
at TCP.onread (net.js:402:27)
我有一行代码,每当发出通知事件时,都会记录现有的侦听器。我已经运行了一段时间,它显示每个订阅的客户端只有一个侦听器(应该是这样),但当我收到警告消息时,代码中没有这一行。代码完全相同,只是那一行很难。
这是推送服务器的代码(这有点初级,因为我还在学习Node.js):
var http = require('http');
var url = require("url");
var qs = require("querystring");
var events = require('events');
var util = require('util');
var emitter = new events.EventEmitter;
function onRequest(request, response)
{
var pathname = url.parse(request.url).pathname;
console.log("Request for " + pathname + " received.");
request.setEncoding("utf8");
if (request.method == 'POST')
{
var postData = "";
request.addListener("data", function(postDataChunk)
{
postData += postDataChunk;
console.log("Received POST data chunk '"+ postDataChunk + "'.");
});
request.addListener("end", function()
{
route(pathname, response, postData);
});
}
else if (request.method=='GET')
{
var urlParts = url.parse(request.url, true);
route(pathname, response, urlParts.query);
}
}
function route(pathname, response, data)
{
switch (pathname)
{
case "/subscription":
emitter.once("event:notify", function(ids)
{
response.writeHead(200, {"Content-Type": "text/html", "Access-Control-Allow-Origin": "*"});
response.write(JSON.stringify(ids));
response.end();
});
break;
case "/notification":
//show how many listeners exist
console.log(util.inspect(emitter.listeners('event:notify'));
emitter.emit("event:notify", data.ids);
response.writeHead(200, {"Content-Type": "text/html", "Access-Control-Allow-Origin": "*"});
response.write(JSON.stringify(true));
response.end();
break;
default:
console.log("No request handler found for " + pathname);
response.writeHead(404, {"Content-Type": "text/plain", "Access-Control-Allow-Origin": "*"});
response.write("404 - Not found");
response.end();
break;
}
}
http.createServer(onRequest).listen(8888);
console.log('Server running at http://127.0.0.1:8888/');
我的印象是,一旦使用emitter.once,它就会自动删除事件侦听器,所以我不知道如果只有一个客户端连接,怎么会添加11个侦听器。我认为,如果客户端在等待通知时断开连接,那么相关的连接资源可能不会被释放。
我想知道我是否必须手动处理断开连接,以及是否真的有泄漏。欢迎任何建议。谢谢
如果有人感兴趣,上面的代码确实会泄漏。当客户端在发送通知之前断开连接时,就会发生泄漏。要解决此问题,有必要在客户端突然断开连接时删除事件侦听器,例如:
case "/subscription":
var notify = function(ids)
{
response.writeHead(200, {"Content-Type": "text/html", "Access-Control-Allow-Origin": "*"});
response.write(JSON.stringify(ids));
response.end();
}
emitter.once("event:notify", notify);
//event will be removed when connection is closed
request.on("close", function()
{
emitter.removeListener("event:notify", notify);
});
break;