forked from mirrors/gecko-dev
116 lines
3.8 KiB
JavaScript
116 lines
3.8 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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// This implements logic for stopping requests if the server starts to return
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// too many errors. If we get MAX_ERRORS errors in ERROR_PERIOD minutes, we
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// back off for TIMEOUT_INCREMENT minutes. If we get another error
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// immediately after we restart, we double the timeout and add
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// TIMEOUT_INCREMENT minutes, etc.
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//
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// This is similar to the logic used by the search suggestion service.
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// HTTP responses that count as an error. We also include any 5xx response
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// as an error.
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this.HTTP_FOUND = 302;
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this.HTTP_SEE_OTHER = 303;
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this.HTTP_TEMPORARY_REDIRECT = 307;
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/**
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* @param maxErrors Number of times to request before backing off.
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* @param retryIncrement Time (ms) for each retry before backing off.
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* @param maxRequests Number the number of requests needed to trigger backoff
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* @param requestPeriod Number time (ms) in which maxRequests have to occur to
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* trigger the backoff behavior (0 to disable maxRequests)
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* @param timeoutIncrement Number time (ms) the starting timeout period
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* we double this time for consecutive errors
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* @param maxTimeout Number time (ms) maximum timeout period
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*/
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this.RequestBackoff =
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function RequestBackoff(maxErrors, retryIncrement,
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maxRequests, requestPeriod,
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timeoutIncrement, maxTimeout) {
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this.MAX_ERRORS_ = maxErrors;
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this.RETRY_INCREMENT_ = retryIncrement;
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this.MAX_REQUESTS_ = maxRequests;
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this.REQUEST_PERIOD_ = requestPeriod;
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this.TIMEOUT_INCREMENT_ = timeoutIncrement;
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this.MAX_TIMEOUT_ = maxTimeout;
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// Queue of ints keeping the time of all requests
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this.requestTimes_ = [];
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this.numErrors_ = 0;
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this.errorTimeout_ = 0;
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this.nextRequestTime_ = 0;
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}
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/**
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* Reset the object for reuse. This deliberately doesn't clear requestTimes_.
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*/
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RequestBackoff.prototype.reset = function() {
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this.numErrors_ = 0;
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this.errorTimeout_ = 0;
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this.nextRequestTime_ = 0;
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}
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/**
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* Check to see if we can make a request.
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*/
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RequestBackoff.prototype.canMakeRequest = function() {
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var now = Date.now();
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if (now < this.nextRequestTime_) {
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return false;
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}
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return (this.requestTimes_.length < this.MAX_REQUESTS_ ||
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(now - this.requestTimes_[0]) > this.REQUEST_PERIOD_);
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}
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RequestBackoff.prototype.noteRequest = function() {
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var now = Date.now();
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this.requestTimes_.push(now);
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// We only care about keeping track of MAX_REQUESTS
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if (this.requestTimes_.length > this.MAX_REQUESTS_)
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this.requestTimes_.shift();
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}
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RequestBackoff.prototype.nextRequestDelay = function() {
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return Math.max(0, this.nextRequestTime_ - Date.now());
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}
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/**
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* Notify this object of the last server response. If it's an error,
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*/
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RequestBackoff.prototype.noteServerResponse = function(status) {
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if (this.isErrorStatus(status)) {
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this.numErrors_++;
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if (this.numErrors_ < this.MAX_ERRORS_)
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this.errorTimeout_ = this.RETRY_INCREMENT_;
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else if (this.numErrors_ == this.MAX_ERRORS_)
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this.errorTimeout_ = this.TIMEOUT_INCREMENT_;
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else
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this.errorTimeout_ *= 2;
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this.errorTimeout_ = Math.min(this.errorTimeout_, this.MAX_TIMEOUT_);
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this.nextRequestTime_ = Date.now() + this.errorTimeout_;
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} else {
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// Reset error timeout, allow requests to go through.
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this.reset();
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}
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}
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/**
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* We consider 302, 303, 307, 4xx, and 5xx http responses to be errors.
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* @param status Number http status
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* @return Boolean true if we consider this http status an error
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*/
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RequestBackoff.prototype.isErrorStatus = function(status) {
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return ((400 <= status && status <= 599) ||
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HTTP_FOUND == status ||
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HTTP_SEE_OTHER == status ||
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HTTP_TEMPORARY_REDIRECT == status);
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}
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