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/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Google Safe Browsing.
*
* The Initial Developer of the Original Code is Google Inc.
* Portions created by the Initial Developer are Copyright (C) 2006
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Tony Chang <tc@google.com> (original author)
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
// 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.
const HTTP_FOUND = 302;
const HTTP_SEE_OTHER = 303;
const HTTP_TEMPORARY_REDIRECT = 307;
/**
* @param maxErrors Number the number of errors needed to trigger backoff
* @param errorPeriod Number time (ms) in which maxErros have to occur to
* trigger the backoff behavior
* @param timeoutIncrement Number time (ms) the starting timeout period
* we double this time for consecutive errors
* @param maxTimeout Number time (ms) maximum timeout period
*/
function RequestBackoff(maxErrors, errorPeriod, timeoutIncrement, maxTimeout) {
this.MAX_ERRORS_ = maxErrors;
this.ERROR_PERIOD_ = errorPeriod;
this.TIMEOUT_INCREMENT_ = timeoutIncrement;
this.MAX_TIMEOUT_ = maxTimeout;
// Queue of ints keeping the time of errors.
this.errorTimes_ = [];
this.errorTimeout_ = 0;
this.nextRequestTime_ = 0;
this.backoffTriggered_ = false;
}
/**
* Reset the object for reuse.
*/
RequestBackoff.prototype.reset = function() {
this.errorTimes_ = [];
this.errorTimeout_ = 0;
this.nextRequestTime_ = 0;
this.backoffTriggered_ = false;
}
/**
* Check to see if we can make a request.
*/
RequestBackoff.prototype.canMakeRequest = function() {
return Date.now() > this.nextRequestTime_;
}
/**
* Notify this object of the last server response. If it's an error, we
* check to see if we should trigger a backoff.
* @return Boolean true if this counts as an error.
*/
RequestBackoff.prototype.noteServerResponse = function(status) {
var isError = this.isErrorStatus_(status);
if (isError) {
var now = Date.now();
this.errorTimes_.push(now);
// We only care about keeping track of MAX_ERRORS
if (this.errorTimes_.length > this.MAX_ERRORS_)
this.errorTimes_.shift();
// See if we hit the backoff case
// This either means we hit MAX_ERRORS in ERROR_PERIOD
// *or* we were already in a backoff state, in which case we
// increase our timeout.
if ((this.errorTimes_.length == this.MAX_ERRORS_ &&
now - this.errorTimes_[0] < this.ERROR_PERIOD_)
|| this.backoffTriggered_) {
this.errorTimeout_ = (this.errorTimeout_ * 2) + this.TIMEOUT_INCREMENT_;
this.errorTimeout_ = Math.min(this.errorTimeout_, this.MAX_TIMEOUT_);
this.nextRequestTime_ = now + this.errorTimeout_;
this.backoffTriggered_ = true;
}
} else {
// Reset error timeout, allow requests to go through, and switch out
// of backoff state.
this.errorTimeout_ = 0;
this.nextRequestTime_ = 0;
this.backoffTriggered_ = false;
}
return isError;
}
/**
* We consider 302, 303, 307, 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 ((500 <= status && status <= 599) ||
HTTP_FOUND == status ||
HTTP_SEE_OTHER == status ||
HTTP_TEMPORARY_REDIRECT == status);
}
#ifdef 0
// Some unittests (e.g., paste into JS shell)
var jslib = Cc["@mozilla.org/url-classifier/jslib;1"].
getService().wrappedJSObject;
var _Datenow = jslib.Date.now;
function setNow(time) {
jslib.Date.now = function() {
return time;
}
}
// 2 errors, 5ms time period, 5ms backoff interval, 20ms max delay
var rb = new jslib.RequestBackoff(2, 5, 5, 20);
setNow(1);
rb.noteServerResponse(200)
if (!rb.canMakeRequest()) throw "expected ok";
setNow(2);
rb.noteServerResponse(500);
if (!rb.canMakeRequest()) throw "expected ok";
setNow(3);
rb.noteServerResponse(200)
if (!rb.canMakeRequest()) throw "expected ok";
// Trigger backoff
setNow(4);
rb.noteServerResponse(502)
if (rb.canMakeRequest()) throw "expected failed";
if (rb.nextRequestTime_ != 9) throw "wrong next request time";
// Trigger backoff again
setNow(10);
if (!rb.canMakeRequest()) throw "expected ok";
rb.noteServerResponse(503)
if (rb.canMakeRequest()) throw "expected failed";
if (rb.nextRequestTime_ != 25) throw "wrong next request time";
// Trigger backoff a third time and hit max timeout
setNow(30);
if (!rb.canMakeRequest()) throw "expected ok";
rb.noteServerResponse(302)
if (rb.canMakeRequest()) throw "expected failed";
if (rb.nextRequestTime_ != 50) throw "wrong next request time";
// Request goes through
setNow(100);
if (!rb.canMakeRequest()) throw "expected ok";
rb.noteServerResponse(200)
if (!rb.canMakeRequest()) throw "expected ok";
if (rb.nextRequestTime_ != 0) throw "wrong next request time";
// Another error (shouldn't trigger backoff)
setNow(101);
rb.noteServerResponse(500);
if (!rb.canMakeRequest()) throw "expected ok";
// Another error, but not in ERROR_PERIOD, so it should be ok
setNow(107);
rb.noteServerResponse(500);
if (!rb.canMakeRequest()) throw "expected ok";
jslib.Date.now = _Datenow;
#endif
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