1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/toolkit/components/url-classifier/content/request-backoff.js Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,115 @@
1.4 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.5 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.6 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.7 +
1.8 +// This implements logic for stopping requests if the server starts to return
1.9 +// too many errors. If we get MAX_ERRORS errors in ERROR_PERIOD minutes, we
1.10 +// back off for TIMEOUT_INCREMENT minutes. If we get another error
1.11 +// immediately after we restart, we double the timeout and add
1.12 +// TIMEOUT_INCREMENT minutes, etc.
1.13 +//
1.14 +// This is similar to the logic used by the search suggestion service.
1.15 +
1.16 +// HTTP responses that count as an error. We also include any 5xx response
1.17 +// as an error.
1.18 +const HTTP_FOUND = 302;
1.19 +const HTTP_SEE_OTHER = 303;
1.20 +const HTTP_TEMPORARY_REDIRECT = 307;
1.21 +
1.22 +/**
1.23 + * @param maxErrors Number of times to request before backing off.
1.24 + * @param retryIncrement Time (ms) for each retry before backing off.
1.25 + * @param maxRequests Number the number of requests needed to trigger backoff
1.26 + * @param requestPeriod Number time (ms) in which maxRequests have to occur to
1.27 + * trigger the backoff behavior
1.28 + * @param timeoutIncrement Number time (ms) the starting timeout period
1.29 + * we double this time for consecutive errors
1.30 + * @param maxTimeout Number time (ms) maximum timeout period
1.31 + */
1.32 +function RequestBackoff(maxErrors, retryIncrement,
1.33 + maxRequests, requestPeriod,
1.34 + timeoutIncrement, maxTimeout) {
1.35 + this.MAX_ERRORS_ = maxErrors;
1.36 + this.RETRY_INCREMENT_ = retryIncrement;
1.37 + this.MAX_REQUESTS_ = maxRequests;
1.38 + this.REQUEST_PERIOD_ = requestPeriod;
1.39 + this.TIMEOUT_INCREMENT_ = timeoutIncrement;
1.40 + this.MAX_TIMEOUT_ = maxTimeout;
1.41 +
1.42 + // Queue of ints keeping the time of all requests
1.43 + this.requestTimes_ = [];
1.44 +
1.45 + this.numErrors_ = 0;
1.46 + this.errorTimeout_ = 0;
1.47 + this.nextRequestTime_ = 0;
1.48 +}
1.49 +
1.50 +/**
1.51 + * Reset the object for reuse.
1.52 + */
1.53 +RequestBackoff.prototype.reset = function() {
1.54 + this.numErrors_ = 0;
1.55 + this.errorTimeout_ = 0;
1.56 + this.nextRequestTime_ = 0;
1.57 +}
1.58 +
1.59 +/**
1.60 + * Check to see if we can make a request.
1.61 + */
1.62 +RequestBackoff.prototype.canMakeRequest = function() {
1.63 + var now = Date.now();
1.64 + if (now < this.nextRequestTime_) {
1.65 + return false;
1.66 + }
1.67 +
1.68 + return (this.requestTimes_.length < this.MAX_REQUESTS_ ||
1.69 + (now - this.requestTimes_[0]) > this.REQUEST_PERIOD_);
1.70 +}
1.71 +
1.72 +RequestBackoff.prototype.noteRequest = function() {
1.73 + var now = Date.now();
1.74 + this.requestTimes_.push(now);
1.75 +
1.76 + // We only care about keeping track of MAX_REQUESTS
1.77 + if (this.requestTimes_.length > this.MAX_REQUESTS_)
1.78 + this.requestTimes_.shift();
1.79 +}
1.80 +
1.81 +RequestBackoff.prototype.nextRequestDelay = function() {
1.82 + return Math.max(0, this.nextRequestTime_ - Date.now());
1.83 +}
1.84 +
1.85 +/**
1.86 + * Notify this object of the last server response. If it's an error,
1.87 + */
1.88 +RequestBackoff.prototype.noteServerResponse = function(status) {
1.89 + if (this.isErrorStatus(status)) {
1.90 + this.numErrors_++;
1.91 +
1.92 + if (this.numErrors_ < this.MAX_ERRORS_)
1.93 + this.errorTimeout_ = this.RETRY_INCREMENT_;
1.94 + else if (this.numErrors_ == this.MAX_ERRORS_)
1.95 + this.errorTimeout_ = this.TIMEOUT_INCREMENT_;
1.96 + else
1.97 + this.errorTimeout_ *= 2;
1.98 +
1.99 + this.errorTimeout_ = Math.min(this.errorTimeout_, this.MAX_TIMEOUT_);
1.100 + this.nextRequestTime_ = Date.now() + this.errorTimeout_;
1.101 + } else {
1.102 + // Reset error timeout, allow requests to go through.
1.103 + this.reset();
1.104 + }
1.105 +}
1.106 +
1.107 +/**
1.108 + * We consider 302, 303, 307, 4xx, and 5xx http responses to be errors.
1.109 + * @param status Number http status
1.110 + * @return Boolean true if we consider this http status an error
1.111 + */
1.112 +RequestBackoff.prototype.isErrorStatus = function(status) {
1.113 + return ((400 <= status && status <= 599) ||
1.114 + HTTP_FOUND == status ||
1.115 + HTTP_SEE_OTHER == status ||
1.116 + HTTP_TEMPORARY_REDIRECT == status);
1.117 +}
1.118 +
