WebSocket连接超时

Question

我正在尝试实现failafe websocket包装器.而我遇到的问题是处理超时错误.逻辑应该是:如果套接字在$ timeoutInMiliseconds期间没有打开 - 它必须关闭并重新打开$ N次.

我写的是这样的.

var maxReconects = 0;
var ws = new WebSocket(url);
var onCloseHandler = function() {
    if ( maxReconects < N ) {
        maxReconects++;
        // construct new Websocket 
        ....
    }
};
ws.onclose = onCloseHandler;
var timeout = setTimeout(function() {
                console.log("Socket connection timeout",ws.readyState);
                timedOut = true;
                ws.close();  <--- ws.readyState is 0 here 
                timedOut = false;
},timeoutInMiliseconds); 

但问题是正确处理超时websockets - 如果我试图关闭未连接的套接字我在chrome中收到警告:

"与'ws://127.0.0.1:9010/timeout'的WebSocket连接失败:在建立连接之前WebSocket已关闭."

我不知道如何避免它 - ws接口没有中止功能.

我尝试过的另一个方法是在超时时关闭套接字,如果它没有连接,只是将其标记为不使用更多,如果接收到readyState不止一个就关闭它 - 但是它可能产生可能的泄漏,并且对于这样简单的任务来说很复杂.

Answer 1

我编写了以下代码，用于打开带有 timeout 和 retries 的 websocket 故障安全，有关更多详细信息，请参阅代码中的注释。

用法- 打开具有 5000 毫秒超时和 10 次重试（最大）的 websocket：

initWebsocket('ws:\\localhost:8090', null, 5000, 10).then(function(socket){
    console.log('socket initialized!');
    //do something with socket...

    //if you want to use the socket later again and assure that it is still open:
    initWebsocket('ws:\\localhost:8090', socket, 5000, 10).then(function(socket){
        //if socket is still open, you are using the same "socket" object here
        //if socket was closed, you are using a new opened "socket" object
    }

}, function(){
    console.log('init of socket failed!');
});

initWebsocket()在库或类似的地方定义的方法：

/**
 * inits a websocket by a given url, returned promise resolves with initialized websocket, rejects after failure/timeout.
 *
 * @param url the websocket url to init
 * @param existingWebsocket if passed and this passed websocket is already open, this existingWebsocket is resolved, no additional websocket is opened
 * @param timeoutMs the timeout in milliseconds for opening the websocket
 * @param numberOfRetries the number of times initializing the socket should be retried, if not specified or 0, no retries are made
 *        and a failure/timeout causes rejection of the returned promise
 * @return {Promise}
 */
function initWebsocket(url, existingWebsocket, timeoutMs, numberOfRetries) {
    timeoutMs = timeoutMs ? timeoutMs : 1500;
    numberOfRetries = numberOfRetries ? numberOfRetries : 0;
    var hasReturned = false;
    var promise = new Promise((resolve, reject) => {
        setTimeout(function () {
            if(!hasReturned) {
                console.info('opening websocket timed out: ' + url);
                rejectInternal();
            }
        }, timeoutMs);
        if (!existingWebsocket || existingWebsocket.readyState != existingWebsocket.OPEN) {
            if (existingWebsocket) {
                existingWebsocket.close();
            }
            var websocket = new WebSocket(url);
            websocket.onopen = function () {
                if(hasReturned) {
                    websocket.close();
                } else {
                    console.info('websocket to opened! url: ' + url);
                    resolve(websocket);
                }
            };
            websocket.onclose = function () {
                console.info('websocket closed! url: ' + url);
                rejectInternal();
            };
            websocket.onerror = function () {
                console.info('websocket error! url: ' + url);
                rejectInternal();
            };
        } else {
            resolve(existingWebsocket);
        }

        function rejectInternal() {
            if(numberOfRetries <= 0) {
                reject();
            } else if(!hasReturned) {
                hasReturned = true;
                console.info('retrying connection to websocket! url: ' + url + ', remaining retries: ' + (numberOfRetries-1));
                initWebsocket(url, null, timeoutMs, numberOfRetries-1).then(resolve, reject);
            }
        }
    });
    promise.then(function () {hasReturned = true;}, function () {hasReturned = true;});
    return promise;
};

更好的解决方案是将功能封装在自己的类中FailsafeWebsocket或其他任何东西中。然而，这个解决方案在我的项目中已经足够了 - 也许它也可以帮助其他人。

Answer 2

您的timeout变量被分配给setTimeout(...正在词法调用的函数。当您的代码到达时，var onCloseHander = ...您的timeout函数已经被调用。

解决这个问题的方法是创建一个makeTimeout函数：

var makeTimeout = function (timeoutInMiliseconds) {
    return window.setTimeout(function() {
        // do stuff
    }, timeoutInMiliseconds)
};

var timeoutId = makeTimeout(100)将调用该setTimeout函数并将其设置timeoutId为超时 ID 的值。如果您需要取消此超时，可以通过调用 来完成window.clearTimeout(timeoutId)。