1 files changed, 116 insertions, 0 deletions
diff --git a/toolkit/components/url-classifier/content/request-backoff.js b/toolkit/components/url-classifier/content/request-backoff.js
new file mode 100644
index 000000000..17e815cf1
--- /dev/null
+++ b/toolkit/components/url-classifier/content/request-backoff.js
@@ -0,0 +1,116 @@
+/* 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);
+}
+