Add chrome to the repository.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@15 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 169 insertions, 0 deletions

diff --git a/chrome/browser/url_fetcher_protect.h b/chrome/browser/url_fetcher_protect.h
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+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// This file implements backoff in the suggest system so that we don't
+// DOS the Suggest servers when using URLFetcher.
+
+#ifndef CHROME_BROWSER_URL_FETCHER_PROTECT_H__
+#define CHROME_BROWSER_URL_FETCHER_PROTECT_H__
+
+#include <map>
+#include <queue>
+#include <string>
+
+#include "base/lock.h"
+#include "base/logging.h"
+#include "base/scoped_ptr.h"
+#include "base/time.h"
+
+
+// This class is used to manage one service's rate protection. It maintains
+// a queue of connection successes and failures and analyzes the requests
+// over some period of time, in order to deduce the backoff time of every
+// request.
+// The backoff algorithm consists of two parts. Firstly, avoid too many
+// send events in a sliding window. That will prevent traffic overload.
+// Secondly, exponential backoff is used when receiving an error message
+// from server. Exponential backoff period is calculated using the following
+// formula:
+//
+//             initial backoff time      (the first time to receive error)
+//  backoff =  k * current_backoff + c   (the second, third, ... error)
+//             maximum backoff time      (when backoff > maximum backoff time)
+//
+// where |k| is the multiplier, and |c| is the constant factor.
+class ProtectEntry {
+ public:
+  enum EventType {
+    SEND,      // request will be sent out
+    SUCCESS,   // successful response
+    FAILURE    // no response or error
+  };
+
+  ProtectEntry();
+  ProtectEntry(int sliding_window_period, int max_send_threshold,
+               int max_retries, int initial_timeout,
+               double multiplier, int constant_factor,
+               int maximum_timeout);
+
+
+  virtual ~ProtectEntry() { }
+
+  // When a connection event happens, log it to the queue, and recalculate
+  // the timeout period. It returns the backoff time, in milliseconds, that
+  // indicates to the sender how long should it wait before sending the request.
+  // If the request is allowed to be sent immediately, the backoff time is 0.
+  int UpdateBackoff(EventType event_type);
+
+  // Returns the max retries allowed.
+  int max_retries() const {
+    return max_retries_;
+  }
+
+ private:
+  // When a request comes, calculate the release time for it.
+  // Returns the backoff time before sending.
+  TimeDelta AntiOverload();
+  // Resets backoff when service is ok.
+  // Returns the backoff time before sending.
+  TimeDelta ResetBackoff();
+  // Calculates new backoff when encountering a failure.
+  // Returns the backoff time before sending.
+  TimeDelta IncreaseBackoff();
+
+  // Default parameters.  Time is in milliseconds.
+  static const int kDefaultSlidingWindowPeriod;
+  static const int kDefaultMaxSendThreshold;
+  static const int kDefaultMaxRetries;
+  static const int kDefaultInitialTimeout;
+  static const double kDefaultMultiplier;
+  static const int kDefaultConstantFactor;
+  static const int kDefaultMaximumTimeout;
+
+  // time to consider events when checking backoff
+  int sliding_window_period_;
+
+  // maximum number of requests allowed in sliding window period
+  int max_send_threshold_;
+  // maximum retris allowed
+  int max_retries_;
+
+  // initial timeout on first failure
+  int initial_timeout_;
+  // factor by which to multiply on exponential backoff (e.g., 2.0)
+  double multiplier_;
+  // constant time term to add to each attempt
+  int constant_factor_;
+  // maximum amount of time between requests
+  int maximum_timeout_;
+
+  // current exponential backoff period
+  int timeout_period_;
+  // time that protection is scheduled to end
+  TimeTicks release_time_;
+
+  // Sets up a lock to ensure thread safe.
+  Lock lock_;
+
+  // A list of the recent send events. We ues them to decide whether
+  // there are too many requests sent in sliding window.
+  std::queue<TimeTicks> send_log_;
+
+  DISALLOW_EVIL_CONSTRUCTORS(ProtectEntry);
+};
+
+
+// This singleton class is used to manage all protect entries.
+// Now we use the host name as service id.
+class ProtectManager {
+ public:
+  ~ProtectManager();
+
+  // Returns the global instance of this class.
+  static ProtectManager* GetInstance();
+
+  // Registers a new entry in this service. If the entry already exists,
+  // just returns it.
+  ProtectEntry* Register(std::string id);
+  // Always registers the entry even when it exists.
+  ProtectEntry* Register(std::string id, ProtectEntry* entry);
+
+ private:
+  ProtectManager() { }
+
+  typedef std::map<const std::string, ProtectEntry*> ProtectService;
+
+  static Lock lock_;
+  static scoped_ptr<ProtectManager> protect_manager_;
+  ProtectService services_;
+
+  DISALLOW_EVIL_CONSTRUCTORS(ProtectManager);
+};
+
+#endif  // CHROME_BROWSER_URL_FETCHER_PROTECT_H__