Implement exponential back-off mechanism and enforce it at the URLRequestHttpJob level.

chrome/common/net/url_fetcher_protect.cc

-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "chrome/common/net/url_fetcher_protect.h"
-
-#include "base/logging.h"
-
-// URLFetcherProtectEntry ----------------------------------------------------
-
-using base::TimeDelta;
-using base::TimeTicks;
-
-// Default parameters.  Time is in milliseconds.
-// static
-const int URLFetcherProtectEntry::kDefaultSlidingWindowPeriod = 2000;
-
-const int URLFetcherProtectEntry::kDefaultMaxSendThreshold = 20;
-const int URLFetcherProtectEntry::kDefaultMaxRetries = 0;
-
-const int URLFetcherProtectEntry::kDefaultInitialTimeout = 100;
-const double URLFetcherProtectEntry::kDefaultMultiplier = 2.0;
-const int URLFetcherProtectEntry::kDefaultConstantFactor = 100;
-const int URLFetcherProtectEntry::kDefaultMaximumTimeout = 60000;
-
-
-URLFetcherProtectEntry::URLFetcherProtectEntry()
-    : sliding_window_period_(kDefaultSlidingWindowPeriod),
-      max_send_threshold_(kDefaultMaxSendThreshold),
-      max_retries_(kDefaultMaxRetries),
-      initial_timeout_(kDefaultInitialTimeout),
-      multiplier_(kDefaultMultiplier),
-      constant_factor_(kDefaultConstantFactor),
-      maximum_timeout_(kDefaultMaximumTimeout) {
-  ResetBackoff();
-}
-
-URLFetcherProtectEntry::URLFetcherProtectEntry(int sliding_window_period,
-                                               int max_send_threshold,
-                                               int max_retries,
-                                               int initial_timeout,
-                                               double multiplier,
-                                               int constant_factor,
-                                               int maximum_timeout)
-    : sliding_window_period_(sliding_window_period),
-      max_send_threshold_(max_send_threshold),
-      max_retries_(max_retries),
-      initial_timeout_(initial_timeout),
-      multiplier_(multiplier),
-      constant_factor_(constant_factor),
-      maximum_timeout_(maximum_timeout) {
-  ResetBackoff();
-}
-
-URLFetcherProtectEntry::~URLFetcherProtectEntry() {}
-
-int64 URLFetcherProtectEntry::UpdateBackoff(EventType event_type) {
-  // request may be sent in different threads
-  AutoLock lock(lock_);
-
-  TimeDelta t;
-  switch (event_type) {
-    case SEND:
-      t = AntiOverload();
-      break;
-    case SUCCESS:
-      t = ResetBackoff();
-      break;
-    case FAILURE:
-      t = IncreaseBackoff();
-      break;
-    default:
-      NOTREACHED();
-  }
-
-  int64 wait = t.InMilliseconds();
-  DCHECK(wait >= 0);
-  return wait;
-}
-
-TimeDelta URLFetcherProtectEntry::AntiOverload() {
-  TimeDelta sw = TimeDelta::FromMilliseconds(sliding_window_period_);
-  TimeTicks now = TimeTicks::Now();
-  // Estimate when the next request will be sent.
-  release_time_ = now;
-  if (send_log_.size() > 0) {
-    release_time_ = std::max(release_time_, send_log_.back());
-  }
-  // Checks if there are too many send events in recent time.
-  if (send_log_.size() >= static_cast<unsigned>(max_send_threshold_)) {
-    release_time_ = std::max(release_time_, send_log_.front() + sw);
-  }
-  // Logs the new send event.
-  send_log_.push(release_time_);
-  // Drops the out-of-date events in the event list.
-  while (!send_log_.empty() &&
-         (send_log_.front() + sw <= send_log_.back())) {
-    send_log_.pop();
-  }
-  return release_time_ - now;
-}
-
-TimeDelta URLFetcherProtectEntry::ResetBackoff() {
-  timeout_period_ = initial_timeout_;
-  release_time_ = TimeTicks::Now();
-  return TimeDelta::FromMilliseconds(0);
-}
-
-TimeDelta URLFetcherProtectEntry::IncreaseBackoff() {
-  TimeTicks now = TimeTicks::Now();
-
-  release_time_ = std::max(release_time_, now) +
-                  TimeDelta::FromMilliseconds(timeout_period_);
-
-  // Calculates the new backoff time.
-  timeout_period_ = static_cast<int>
-      (multiplier_ * timeout_period_ + constant_factor_);
-  if (maximum_timeout_ && timeout_period_ > maximum_timeout_)
-    timeout_period_ = maximum_timeout_;
-
-  return release_time_ - now;
-}
-
-// URLFetcherProtectManager --------------------------------------------------
-
-// static
-scoped_ptr<URLFetcherProtectManager> URLFetcherProtectManager::protect_manager_;
-Lock URLFetcherProtectManager::lock_;
-
-URLFetcherProtectManager::~URLFetcherProtectManager() {
-  // Deletes all entries
-  ProtectService::iterator i;
-  for (i = services_.begin(); i != services_.end(); ++i) {
-    if (i->second)
-      delete i->second;
-  }
-}
-
-// static
-URLFetcherProtectManager* URLFetcherProtectManager::GetInstance() {
-  AutoLock lock(lock_);
-
-  if (protect_manager_.get() == NULL) {
-    protect_manager_.reset(new URLFetcherProtectManager());
-  }
-  return protect_manager_.get();
-}
-
-URLFetcherProtectEntry* URLFetcherProtectManager::Register(
-    const std::string& id) {
-  AutoLock lock(lock_);
-
-  ProtectService::iterator i = services_.find(id);
-
-  if (i != services_.end()) {
-    // The entry exists.
-    return i->second;
-  }
-
-  // Creates a new entry.
-  URLFetcherProtectEntry* entry = new URLFetcherProtectEntry();
-  services_[id] = entry;
-  return entry;
-}
-
-URLFetcherProtectEntry* URLFetcherProtectManager::Register(
-    const std::string& id, URLFetcherProtectEntry* entry) {
-  AutoLock lock(lock_);
-
-  ProtectService::iterator i = services_.find(id);
-  if (i != services_.end()) {
-    // The entry exists.
-    delete i->second;
-  }
-
-  services_[id] = entry;
-  return entry;
-}
-
-URLFetcherProtectManager::URLFetcherProtectManager() {}