diff options
| -rw-r--r-- | README | 34 | ||||
| -rw-r--r-- | polldance.js | 174 |
2 files changed, 152 insertions, 56 deletions
@@ -4,10 +4,11 @@ Date: January 28th, 2013 Authors: Justin Karneges <justin@fanout.io> Katsuyuki Ohmuro <harmony7@pex2.jp> -PollDance is a general purpose AJAX library, implementing multiple transports +PollDance is a general-purpose AJAX library, implementing multiple transports to ensure cross-domain access works in all major browsers. It also provides conveniences for long-polling applications such as retries, exponential -backoff between requests, and randomized request delaying. +backoff between requests, randomized request delaying, and workarounds for +browser "busy" indications. Dependencies: @@ -29,27 +30,28 @@ Limitations: Usage: var req = new PollDance.Request(); - req.on('finished', function(code, result) { ... }); + req.on('finished', function(code, result, headers) { ... }); req.on('error', function(reason) { ... }); var headers = { ... }; var body = 'some data'; + req.maxTries = 2; // try twice req.start('POST', 'http://example.com/path', headers, body); -Non-JSON results: +Non-JSON Results: By default, this library will parse response body data as JSON and return an - object to the application. Call setRawResponse(true) to disable this - behavior and have a string returned instead. - -Polling: - - Call setAttempts(number) to enable multiple request attempts, with - exponential backoff. Pass -1 to indicate infinite attempts. Transport - errors or HTTP responses in the 5xx range will cause a retry to occur. Any - other error will be returned to the application. Request objects may be - reused. If reused, a random delay is inserted before starting the next - request. By default this is a value between 0-1000ms. Call setMaxDelay(ms) - to change the upper bound. + object to the application. Set the rawResponse property to true to disable + this behavior and have a string returned instead. + +Polling and Retries: + + Set the maxTries property to enable multiple request attempts, with + exponential backoff. Set maxTries to -1 to indicate infinite attempts. + Transport errors or HTTP responses in the 5xx range will cause a retry to + occur. Any other error will be returned to the application. Request objects + may be reused. If reused, a random delay is inserted before starting the + next request. By default this is a value between 0-1000ms. Set the maxDelay + property to change the upper bound. JSON-P Protocol: diff --git a/polldance.js b/polldance.js index 2991fac..852b935 100644 --- a/polldance.js +++ b/polldance.js @@ -7,9 +7,7 @@ window.console = { log: function () { }, dir: function () { } }; } - // PollDance.Request has on('finished', int code, object result) and on('error', int reason) callback members - // error reasons: 0=http, 1=timeout - // note: failed json parse on http body results in empty object {}, not error + // PollDance.Request has on('finished', int code, object result, object headers) and on('error', int reason) callback members var JsonCallbacks = { id: 0, @@ -35,7 +33,7 @@ newCallbackInfo: function () { var callbackInfo = { id: "cb-" + this.id, - scriptId: "fo-jsonp-script-" + this.id + scriptId: "pd-jsonp-script-" + this.id }; this.id++; return callbackInfo; @@ -93,63 +91,116 @@ } }; + var ErrorTypes = { + "TransportError": 0, + "FormatError": 1, + "TimeoutError": 2 + }; + var TransportTypes = { "Auto": 0, "Xhr": 1, - "Xdr": 2, - "Jsonp": 3 + "Jsonp": 2 }; - var Request = function () { + var Request = function (config) { if (!(this instanceof Request)) { throw new Error("Constructor called as a function"); } + this._events = new Events(); + this._delayNext = false; + + this.rawResponse = false; + this.maxTries = 1; + this.maxDelay = 1000; + + if (config !== undefined) { + if (config.transport !== undefined) + this.transport = config.transport; + if (config.rawResponse !== undefined) + this.rawResponse = config.rawResponse; + if (config.maxTries !== undefined) + this.maxTries = config.maxTries; + if (config.maxDelay !== undefined) + this.maxDelay = config.maxDelay; + } }; Request.prototype.transport = TransportTypes.Auto; Request.prototype.start = function (method, url, headers, body) { var self = this; + + self._tries = 0; + + var delaytime; + if (self._delayNext) { + self._delayNext = false; + delaytime = Math.floor(Math.random() * self.maxDelay); + console.log("polling again in " + delaytime + "ms"); + } else { + delaytime = 0; // always queue the call, to prevent browser "busy" + } + + self._method = method; + self._url = url; + self._headers = headers; + self._body = body; + + self._timer = setTimeout(function() { self._connect(); }, delaytime); + }; + Request.prototype._connect = function () { + var self = this; self._timer = window.setTimeout(function () { self._timeout(); }, TIMEOUT); - if (corsAvailable) { + ++self._tries; + + if (self.transport == TransportTypes.Auto) { + if (corsAvailable) { + self.transport = TransportTypes.Xhr; + } else { + self.transport = TransportTypes.Jsonp; + } + } + + if (self.transport == TransportTypes.Xhr) { self._xhr = new XMLHttpRequest(); self._xhr.onreadystatechange = function () { self._xhr_readystatechange(); }; - self._xhr.open(method, url, true); + self._xhr.open(self._method, self._url, true); - for (var key in headers) { - if (headers.hasOwnProperty(key)) { - self._xhr.setRequestHeader(key, headers[key]); + for (var key in self._headers) { + if (self._headers.hasOwnProperty(key)) { + self._xhr.setRequestHeader(key, self._headers[key]); } } - self._xhr.send(body); + self._xhr.send(self._body); - console.log("PollDance.Request start: " + url + " " + body); + console.log("PollDance.Request start: " + self._url + " " + body); - } else { + } else { // Jsonp this._callbackInfo = JsonCallbacks.newCallbackInfo(); var paramList = []; paramList.push("callback=" + encodeURIComponent("PollDance._getJsonpCallback(\"" + this._callbackInfo.id + "\")")); - if (method != "GET") { - paramList.push("method=" + encodeURIComponent(method)); + if (self._method != "GET") { + paramList.push("method=" + encodeURIComponent(self._method)); } - if (headers) { - paramList.push("headers=" + encodeURIComponent(JSON.stringify(headers))); + if (self._headers) { + paramList.push("headers=" + encodeURIComponent(JSON.stringify(self._headers))); } - if (body) { - paramList.push("body=" + encodeURIComponent(body)); + if (self._body) { + paramList.push("body=" + encodeURIComponent(self._body)); } var params = paramList.join("&"); var src; - if (url.indexOf("?") != -1) { - src = url + "&" + params; + if (self._url.indexOf("?") != -1) { + src = self._url + "&" + params; } else { - src = url + "?" + params; + src = self._url + "?" + params; } console.log("PollDance.Request json-p " + this._callbackInfo.id + " " + src); @@ -185,11 +236,11 @@ script.parentNode.removeChild(script); }; Request.prototype._cancelreq = function () { - if (corsAvailable) { + if (this.transport == TransportTypes.Xhr) { this._xhr.onreadystatechange = function () { } this._xhr.abort(); this._xhr = null; - } else { + } else { // Jsonp console.log("PollDance.Request json-p " + this._callbackInfo.id + " cancel"); this._removeJsonpCallback(this._callbackInfo); this._callbackInfo = null; @@ -203,18 +254,19 @@ window.clearTimeout(this._timer); this._timer = null; - var status = xhr.status; - - if (status) { - var result; - try { - result = JSON.parse(xhr.responseText); - } catch (e) { - result = {}; + if (xhr.status) { + if (xhr.status >= 500 && xhr.status <= 599 && (this.maxTries == -1 || this._tries < this.maxTries)) { + this._retry(); + } else { + // TODO: xhr.getAllResponseHeaders() + this._handle_response(xhr.status, xhr.statusText, {}, xhr.responseText); } - this._finished(status, result); } else { - this._error(0); + if (this.maxTries == -1 || this._tries < this.maxTries) { + this._retry(); + } else { + this._error(ErrorTypes.TransportError); + } } } }; @@ -227,17 +279,59 @@ this._removeJsonpCallback(this._callbackInfo); this._callbackInfo = null; - this._finished(result.status, result.value); + var headers; + if (result.headers !== undefined) { + headers = result.headers; + } else { + headers = {}; + } + + this._handle_response(result.code, result.status, headers, result.body); + }; + Request.prototype._handle_response(code, status, headers, body) { + var result; + if (this.rawResponse) { + result = body; + } else { + try { + result = JSON.parse(body); + } catch (e) { + this._error(ErrorTypes.FormatError); + return; + } + } + this._finished(code, result, headers); }; Request.prototype._timeout = function () { this._timer = null; this._cancelreq(); - this._error(1); + + if (this.maxTries == -1 || this._tries < this.maxTries) { + this._retry(); + } else { + this._error(ErrorTypes.TimeoutError); + } + }; + Request.prototype._retry = function() { + if (this._tries === 1) { + this._retryTime = 1; + } else if (this._tries < 8) { + this._retryTime = this._retryTime * 2; + } + + var delaytime = this._retryTime * 1000; + delaytime += Math.floor(Math.random() * self.maxDelay); + console.log("trying again in " + delaytime + "ms"); + + var self = this; + self._timer = setTimeout(function() { self._connect(); }, delaytime); }; - Request.prototype._finished = function (code, result) { - this._events.trigger('finished', this, code, result); + Request.prototype._finished = function (code, result, headers) { + this._delayNext = true; + this._events.trigger('finished', this, code, result, headers); }; Request.prototype._error = function (reason) { + this._delayNext = true; this._events.trigger('error', this, reason); }; |