我正在使用Google AppEngine的Channel API。由于用户的网络连接,我在重新启动丢失的连接时遇到了一些问题。当你断开互联网连接时,通道会调用onError,但不会调用onClose。就JavaScript对象而言,通道套接字是开放的。
你如何处理由于互联网问题而失去的连接?我想到的是1)当与应用程序中某个通道无关的RPC第一次成功时(这表明互联网再次活跃),通过触发关闭通道并重新打开它;或者2)使用一直运行并ping服务器以获取网络状态的计时器(这就是引入长轮询的目的,以避免以这种方式消耗不需要的资源)。任何其他想法都很好。
观察:当互联网连接断开时,onError会以增量间隔(10秒、20秒、40秒)调用两次。一旦恢复了互联网连接,频道就不会恢复连接。它停止工作,没有任何迹象表明它已经死了。
谢谢。
当您看到javascript控制台时,大概会看到"400未知SID错误"。如果是这样,下面是我的解决方法。这是AngularJS的服务模块,但请查看oneror回调。请尝试这个变通方法,并让我知道它是否有效。
补充道:我忽略了回答你的主要问题,但在我看来,除非真的在"互联网"上ping,否则很难确定你是否连接到了互联网。因此,您可能希望使用一些类似于以下代码的重试逻辑,并进行一些调整。在下面的例子中,我只重试了3次,但您可以通过一些回退来完成更多操作。然而,我认为最好的处理方法是,当应用程序消耗最大重试次数时,你可以向用户指示应用程序丢失了连接,最好显示一个按钮或链接来重新连接到频道服务。
此外,您还可以跟踪服务器端的连接,请参阅:https://developers.google.com/appengine/docs/java/channel/#Java_Tracking_client_connections_and_disconnections
app.factory('channelService', ['$http', '$rootScope', '$timeout',
function($http, $rootScope, $timeout) {
var service = {};
var isConnectionAlive = false;
var callbacks = new Array();
var retryCount = 0;
var MAX_RETRY_COUNT = 3;
service.registerCallback = function(pattern, callback) {
callbacks.push({pattern: pattern, func: callback});
};
service.messageCallback = function(message) {
for (var i = 0; i < callbacks.length; i++) {
var callback = callbacks[i];
if (message.data.match(callback.pattern)) {
$rootScope.$apply(function() {
callback.func(message);
});
}
}
};
service.channelTokenCallback = function(channelToken) {
var channel = new goog.appengine.Channel(channelToken);
service.socket = channel.open();
isConnectionAlive = false;
service.socket.onmessage = service.messageCallback;
service.socket.onerror = function(error) {
console.log('Detected an error on the channel.');
console.log('Channel Error: ' + error.description + '.');
console.log('Http Error Code: ' + error.code);
isConnectionAlive = false;
if (error.description == 'Invalid+token.' || error.description == 'Token+timed+out.') {
console.log('It should be recovered with onclose handler.');
} else {
// In this case, we need to manually close the socket.
// See also: https://code.google.com/p/googleappengine/issues/detail?id=4940
console.log('Presumably it is "Unknown SID Error". Try closing the socket manually.');
service.socket.close();
}
};
service.socket.onclose = function() {
isConnectionAlive = false;
console.log('Reconnecting to a new channel');
openNewChannel();
};
console.log('A channel was opened successfully. Will check the ping in 20 secs.');
$timeout(checkConnection, 20000, false);
};
function openNewChannel(isRetry) {
console.log('Retrieving a clientId.');
if (isRetry) {
retryCount++;
} else {
retryCount = 0;
}
$http.get('/rest/channel')
.success(service.channelTokenCallback)
.error(function(data, status) {
console.log('Can not retrieve a clientId');
if (status != 403 && retryCount <= MAX_RETRY_COUNT) {
console.log('Retrying to obtain a client id')
openNewChannel(true);
}
})
}
function pingCallback() {
console.log('Got a ping from the server.');
isConnectionAlive = true;
}
function checkConnection() {
if (isConnectionAlive) {
console.log('Connection is alive.');
return;
}
if (service.socket == undefined) {
console.log('will open a new connection in 1 sec');
$timeout(openNewChannel, 1000, false);
return;
}
// Ping didn't arrive
// Assuming onclose handler automatically open a new channel.
console.log('Not receiving a ping, closing the connection');
service.socket.close();
}
service.registerCallback(/P/, pingCallback);
openNewChannel();
return service;
}]);