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-rw-r--r--toolkit/components/url-classifier/content/request-backoff.js116
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diff --git a/toolkit/components/url-classifier/content/request-backoff.js b/toolkit/components/url-classifier/content/request-backoff.js
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This implements logic for stopping requests if the server starts to return
+// too many errors. If we get MAX_ERRORS errors in ERROR_PERIOD minutes, we
+// back off for TIMEOUT_INCREMENT minutes. If we get another error
+// immediately after we restart, we double the timeout and add
+// TIMEOUT_INCREMENT minutes, etc.
+//
+// This is similar to the logic used by the search suggestion service.
+
+// HTTP responses that count as an error. We also include any 5xx response
+// as an error.
+this.HTTP_FOUND = 302;
+this.HTTP_SEE_OTHER = 303;
+this.HTTP_TEMPORARY_REDIRECT = 307;
+
+/**
+ * @param maxErrors Number of times to request before backing off.
+ * @param retryIncrement Time (ms) for each retry before backing off.
+ * @param maxRequests Number the number of requests needed to trigger backoff
+ * @param requestPeriod Number time (ms) in which maxRequests have to occur to
+ * trigger the backoff behavior (0 to disable maxRequests)
+ * @param timeoutIncrement Number time (ms) the starting timeout period
+ * we double this time for consecutive errors
+ * @param maxTimeout Number time (ms) maximum timeout period
+ */
+this.RequestBackoff =
+function RequestBackoff(maxErrors, retryIncrement,
+ maxRequests, requestPeriod,
+ timeoutIncrement, maxTimeout) {
+ this.MAX_ERRORS_ = maxErrors;
+ this.RETRY_INCREMENT_ = retryIncrement;
+ this.MAX_REQUESTS_ = maxRequests;
+ this.REQUEST_PERIOD_ = requestPeriod;
+ this.TIMEOUT_INCREMENT_ = timeoutIncrement;
+ this.MAX_TIMEOUT_ = maxTimeout;
+
+ // Queue of ints keeping the time of all requests
+ this.requestTimes_ = [];
+
+ this.numErrors_ = 0;
+ this.errorTimeout_ = 0;
+ this.nextRequestTime_ = 0;
+}
+
+/**
+ * Reset the object for reuse. This deliberately doesn't clear requestTimes_.
+ */
+RequestBackoff.prototype.reset = function() {
+ this.numErrors_ = 0;
+ this.errorTimeout_ = 0;
+ this.nextRequestTime_ = 0;
+}
+
+/**
+ * Check to see if we can make a request.
+ */
+RequestBackoff.prototype.canMakeRequest = function() {
+ var now = Date.now();
+ if (now < this.nextRequestTime_) {
+ return false;
+ }
+
+ return (this.requestTimes_.length < this.MAX_REQUESTS_ ||
+ (now - this.requestTimes_[0]) > this.REQUEST_PERIOD_);
+}
+
+RequestBackoff.prototype.noteRequest = function() {
+ var now = Date.now();
+ this.requestTimes_.push(now);
+
+ // We only care about keeping track of MAX_REQUESTS
+ if (this.requestTimes_.length > this.MAX_REQUESTS_)
+ this.requestTimes_.shift();
+}
+
+RequestBackoff.prototype.nextRequestDelay = function() {
+ return Math.max(0, this.nextRequestTime_ - Date.now());
+}
+
+/**
+ * Notify this object of the last server response. If it's an error,
+ */
+RequestBackoff.prototype.noteServerResponse = function(status) {
+ if (this.isErrorStatus(status)) {
+ this.numErrors_++;
+
+ if (this.numErrors_ < this.MAX_ERRORS_)
+ this.errorTimeout_ = this.RETRY_INCREMENT_;
+ else if (this.numErrors_ == this.MAX_ERRORS_)
+ this.errorTimeout_ = this.TIMEOUT_INCREMENT_;
+ else
+ this.errorTimeout_ *= 2;
+
+ this.errorTimeout_ = Math.min(this.errorTimeout_, this.MAX_TIMEOUT_);
+ this.nextRequestTime_ = Date.now() + this.errorTimeout_;
+ } else {
+ // Reset error timeout, allow requests to go through.
+ this.reset();
+ }
+}
+
+/**
+ * We consider 302, 303, 307, 4xx, and 5xx http responses to be errors.
+ * @param status Number http status
+ * @return Boolean true if we consider this http status an error
+ */
+RequestBackoff.prototype.isErrorStatus = function(status) {
+ return ((400 <= status && status <= 599) ||
+ HTTP_FOUND == status ||
+ HTTP_SEE_OTHER == status ||
+ HTTP_TEMPORARY_REDIRECT == status);
+}
+