Anti-DDoS enhancements: Log to net log, UMA stats, improved policy.

net/url_request/url_request_throttler_entry.h

 // Copyright (c) 2011 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.
 
 #ifndef NET_URL_REQUEST_URL_REQUEST_THROTTLER_ENTRY_H_
 #define NET_URL_REQUEST_URL_REQUEST_THROTTLER_ENTRY_H_
 #pragma once
 
 #include <queue>
 #include <string>
 
 #include "base/basictypes.h"
+#include "base/time.h"
 #include "net/base/backoff_entry.h"
+#include "net/base/net_log.h"
 #include "net/url_request/url_request_throttler_entry_interface.h"
 
 namespace net {
 
 class URLRequestThrottlerManager;
 
 // URLRequestThrottlerEntry represents an entry of URLRequestThrottlerManager.
 // It analyzes requests of a specific URL over some period of time, in order to
 // deduce the back-off time for every request.
 // The back-off algorithm consists of two parts. Firstly, exponential back-off
@@ skipping 38 matching lines @@
 
   // Name of the header that sites can use to opt out of exponential back-off
   // throttling.
   static const char kExponentialThrottlingHeader[];
 
   // Value for exponential throttling header that can be used to opt out of
   // exponential back-off throttling.
   static const char kExponentialThrottlingDisableValue[];
 
   // The manager object's lifetime must enclose the lifetime of this object.
-  explicit URLRequestThrottlerEntry(URLRequestThrottlerManager* manager);
+  explicit URLRequestThrottlerEntry(URLRequestThrottlerManager* manager,
+                                    const std::string& url_id);
 
   // The life span of instances created with this constructor is set to
   // infinite, and the number of initial errors to ignore is set to 0.
   // It is only used by unit tests.
   URLRequestThrottlerEntry(URLRequestThrottlerManager* manager,
+                           const std::string& url_id,
                            int sliding_window_period_ms,
                            int max_send_threshold,
                            int initial_backoff_ms,
                            double multiply_factor,
                            double jitter_factor,
                            int maximum_backoff_ms);
 
   // Used by the manager, returns true if the entry needs to be garbage
   // collected.
   bool IsEntryOutdated() const;
 
   // Causes this entry to never reject requests due to back-off.
   void DisableBackoffThrottling();
 
   // Causes this entry to NULL its manager pointer.
   void DetachManager();
 
   // Implementation of URLRequestThrottlerEntryInterface.
   virtual bool IsDuringExponentialBackoff() const;
   virtual int64 ReserveSendingTimeForNextRequest(
       const base::TimeTicks& earliest_time);
   virtual base::TimeTicks GetExponentialBackoffReleaseTime() const;
   virtual void UpdateWithResponse(
       const std::string& host,
       const URLRequestThrottlerHeaderInterface* response);
-  virtual void ReceivedContentWasMalformed();
+  virtual void ReceivedContentWasMalformed(int response_code);
 
  protected:
   virtual ~URLRequestThrottlerEntry();
 
   void Initialize();
 
+  // Returns true if the given response code is considered an error for
+  // throttling purposes.
+  bool IsConsideredError(int response_code);
+
   // Equivalent to TimeTicks::Now(), virtual to be mockable for testing purpose.
-  virtual base::TimeTicks GetTimeNow() const;
+  virtual base::TimeTicks ImplGetTimeNow() const;
 
   // Used internally to increase release time following a retry-after header.
   void HandleCustomRetryAfter(const std::string& header_value);
 
   // Used internally to handle the opt-out header.
   void HandleThrottlingHeader(const std::string& header_value,
                               const std::string& host);
 
+  // Used internally to keep track of failure->success transitions and
+  // generate statistics about them.
+  void HandleMetricsTracking(int response_code);
+
   // Retrieves the back-off entry object we're using. Used to enable a
   // unit testing seam for dependency injection in tests.
   virtual const BackoffEntry* GetBackoffEntry() const;
   virtual BackoffEntry* GetBackoffEntry();
 
   // Used by tests.
   base::TimeTicks sliding_window_release_time() const {
     return sliding_window_release_time_;
   }
 
@@ skipping 17 matching lines @@
 
   const base::TimeDelta sliding_window_period_;
   const int max_send_threshold_;
 
   // True if DisableBackoffThrottling() has been called on this object.
   bool is_backoff_disabled_;
 
   // Access it through GetBackoffEntry() to allow a unit test seam.
   BackoffEntry backoff_entry_;
 
+  // The time of the last successful response, plus knowledge of whether
+  // the last response was successful or not, let us generate statistics on
+  // the length of perceived downtime for a given URL, and the error count
+  // when such transitions occur. This is useful for experiments with
+  // throttling but will likely become redundant after they are finished.
+  // TODO(joi): Remove when the time is right
+  base::TimeTicks last_successful_response_time_;
+  bool last_response_was_success_;
+
   // Weak back-reference to the manager object managing us.
   URLRequestThrottlerManager* manager_;
 
+  // Canonicalized URL string that this entry is for; used for logging only.
+  std::string url_id_;
+
+  BoundNetLog net_log_;
+
   DISALLOW_COPY_AND_ASSIGN(URLRequestThrottlerEntry);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_URL_REQUEST_THROTTLER_ENTRY_H_