1 // Copyright 2012 The Chromium Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef NET_URL_REQUEST_URL_REQUEST_THROTTLER_ENTRY_H_ 6 #define NET_URL_REQUEST_URL_REQUEST_THROTTLER_ENTRY_H_ 7 8 #include <stdint.h> 9 10 #include <string> 11 12 #include "base/containers/queue.h" 13 #include "base/memory/raw_ptr.h" 14 #include "base/time/time.h" 15 #include "net/base/backoff_entry.h" 16 #include "net/base/net_export.h" 17 #include "net/log/net_log_with_source.h" 18 #include "net/url_request/url_request_throttler_entry_interface.h" 19 20 namespace net { 21 22 class URLRequestThrottlerManager; 23 24 // URLRequestThrottlerEntry represents an entry of URLRequestThrottlerManager. 25 // It analyzes requests of a specific URL over some period of time, in order to 26 // deduce the back-off time for every request. 27 // The back-off algorithm consists of two parts. Firstly, exponential back-off 28 // is used when receiving 5XX server errors or malformed response bodies. 29 // The exponential back-off rule is enforced by URLRequestHttpJob. Any 30 // request sent during the back-off period will be cancelled. 31 // Secondly, a sliding window is used to count recent requests to a given 32 // destination and provide guidance (to the application level only) on whether 33 // too many requests have been sent and when a good time to send the next one 34 // would be. This is never used to deny requests at the network level. 35 class NET_EXPORT URLRequestThrottlerEntry 36 : public URLRequestThrottlerEntryInterface { 37 public: 38 // Sliding window period. 39 static const int kDefaultSlidingWindowPeriodMs; 40 41 // Maximum number of requests allowed in sliding window period. 42 static const int kDefaultMaxSendThreshold; 43 44 // Number of initial errors to ignore before starting exponential back-off. 45 static const int kDefaultNumErrorsToIgnore; 46 47 // Initial delay for exponential back-off. 48 static const int kDefaultInitialDelayMs; 49 50 // Factor by which the waiting time will be multiplied. 51 static const double kDefaultMultiplyFactor; 52 53 // Fuzzing percentage. ex: 10% will spread requests randomly 54 // between 90%-100% of the calculated time. 55 static const double kDefaultJitterFactor; 56 57 // Maximum amount of time we are willing to delay our request. 58 static const int kDefaultMaximumBackoffMs; 59 60 // Time after which the entry is considered outdated. 61 static const int kDefaultEntryLifetimeMs; 62 63 // The manager object's lifetime must enclose the lifetime of this object. 64 URLRequestThrottlerEntry(URLRequestThrottlerManager* manager, 65 const std::string& url_id); 66 67 // The life span of instances created with this constructor is set to 68 // infinite, and the number of initial errors to ignore is set to 0. 69 // It is only used by unit tests. 70 URLRequestThrottlerEntry(URLRequestThrottlerManager* manager, 71 const std::string& url_id, 72 int sliding_window_period_ms, 73 int max_send_threshold, 74 int initial_backoff_ms, 75 double multiply_factor, 76 double jitter_factor, 77 int maximum_backoff_ms); 78 79 URLRequestThrottlerEntry(const URLRequestThrottlerEntry&) = delete; 80 URLRequestThrottlerEntry& operator=(const URLRequestThrottlerEntry&) = delete; 81 82 // Used by the manager, returns true if the entry needs to be garbage 83 // collected. 84 bool IsEntryOutdated() const; 85 86 // Causes this entry to never reject requests due to back-off. 87 void DisableBackoffThrottling(); 88 89 // Causes this entry to NULL its manager pointer. 90 void DetachManager(); 91 92 // Implementation of URLRequestThrottlerEntryInterface. 93 bool ShouldRejectRequest(const URLRequest& request) const override; 94 int64_t ReserveSendingTimeForNextRequest( 95 const base::TimeTicks& earliest_time) override; 96 base::TimeTicks GetExponentialBackoffReleaseTime() const override; 97 void UpdateWithResponse(int status_code) override; 98 void ReceivedContentWasMalformed(int response_code) override; 99 100 protected: 101 ~URLRequestThrottlerEntry() override; 102 103 void Initialize(); 104 105 // Returns true if the given response code is considered a success for 106 // throttling purposes. 107 bool IsConsideredSuccess(int response_code); 108 109 // Equivalent to TimeTicks::Now(), virtual to be mockable for testing purpose. 110 virtual base::TimeTicks ImplGetTimeNow() const; 111 112 // Retrieves the back-off entry object we're using. Used to enable a 113 // unit testing seam for dependency injection in tests. 114 virtual const BackoffEntry* GetBackoffEntry() const; 115 virtual BackoffEntry* GetBackoffEntry(); 116 117 // Used by tests. sliding_window_release_time()118 base::TimeTicks sliding_window_release_time() const { 119 return sliding_window_release_time_; 120 } 121 122 // Used by tests. set_sliding_window_release_time(const base::TimeTicks & release_time)123 void set_sliding_window_release_time(const base::TimeTicks& release_time) { 124 sliding_window_release_time_ = release_time; 125 } 126 127 // Valid and immutable after construction time. 128 BackoffEntry::Policy backoff_policy_; 129 130 private: 131 // Timestamp calculated by the sliding window algorithm for when we advise 132 // clients the next request should be made, at the earliest. Advisory only, 133 // not used to deny requests. 134 base::TimeTicks sliding_window_release_time_; 135 136 // A list of the recent send events. We use them to decide whether there are 137 // too many requests sent in sliding window. 138 base::queue<base::TimeTicks> send_log_; 139 140 const base::TimeDelta sliding_window_period_; 141 const int max_send_threshold_; 142 143 // True if DisableBackoffThrottling() has been called on this object. 144 bool is_backoff_disabled_ = false; 145 146 // Access it through GetBackoffEntry() to allow a unit test seam. 147 BackoffEntry backoff_entry_; 148 149 // Weak back-reference to the manager object managing us. 150 raw_ptr<URLRequestThrottlerManager> manager_; 151 152 // Canonicalized URL string that this entry is for; used for logging only. 153 std::string url_id_; 154 155 NetLogWithSource net_log_; 156 }; 157 158 } // namespace net 159 160 #endif // NET_URL_REQUEST_URL_REQUEST_THROTTLER_ENTRY_H_ 161