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- // Copyright (c) 2012 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 EXTENSIONS_RENDERER_EXTENSION_THROTTLE_ENTRY_H_
- #define EXTENSIONS_RENDERER_EXTENSION_THROTTLE_ENTRY_H_
- #include <stdint.h>
- #include <string>
- #include "base/containers/queue.h"
- #include "base/time/time.h"
- #include "net/base/backoff_entry.h"
- namespace extensions {
- // ExtensionThrottleEntry represents an entry of ExtensionThrottleManager.
- // 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
- // is used when receiving 5XX server errors or malformed response bodies.
- // The exponential back-off rule is enforced by URLRequestHttpJob. Any
- // request sent during the back-off period will be cancelled.
- // Secondly, a sliding window is used to count recent requests to a given
- // destination and provide guidance (to the application level only) on whether
- // too many requests have been sent and when a good time to send the next one
- // would be. This is never used to deny requests at the network level.
- class ExtensionThrottleEntry {
- public:
- // Sliding window period.
- static const int kDefaultSlidingWindowPeriodMs;
- // Maximum number of requests allowed in sliding window period.
- static const int kDefaultMaxSendThreshold;
- // Number of initial errors to ignore before starting exponential back-off.
- static const int kDefaultNumErrorsToIgnore;
- // Initial delay for exponential back-off.
- static const int kDefaultInitialDelayMs;
- // Factor by which the waiting time will be multiplied.
- static const double kDefaultMultiplyFactor;
- // Fuzzing percentage. ex: 10% will spread requests randomly
- // between 90%-100% of the calculated time.
- static const double kDefaultJitterFactor;
- // Maximum amount of time we are willing to delay our request.
- static const int kDefaultMaximumBackoffMs;
- // Time after which the entry is considered outdated.
- static const int kDefaultEntryLifetimeMs;
- // |url_id| is a unique entry ID.
- explicit ExtensionThrottleEntry(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.
- ExtensionThrottleEntry(const std::string& url_id,
- const net::BackoffEntry::Policy* backoff_policy);
- ExtensionThrottleEntry(const ExtensionThrottleEntry&) = delete;
- ExtensionThrottleEntry& operator=(const ExtensionThrottleEntry&) = delete;
- virtual ~ExtensionThrottleEntry();
- // 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();
- // Returns true when we have encountered server errors and are doing
- // exponential back-off.
- bool ShouldRejectRequest() const;
- // Calculates a recommended sending time for the next request and reserves it.
- // The sending time is not earlier than the current exponential back-off
- // release time or |earliest_time|. Moreover, the previous results of
- // the method are taken into account, in order to make sure they are spread
- // properly over time.
- // Returns the recommended delay before sending the next request, in
- // milliseconds. The return value is always positive or 0.
- // Although it is not mandatory, respecting the value returned by this method
- // is helpful to avoid traffic overload.
- int64_t ReserveSendingTimeForNextRequest(
- const base::TimeTicks& earliest_time);
- // Returns the time after which requests are allowed.
- base::TimeTicks GetExponentialBackoffReleaseTime() const;
- // This method needs to be called each time a response is received.
- void UpdateWithResponse(int status_code);
- // Lets higher-level modules, that know how to parse particular response
- // bodies, notify of receiving malformed content for the given URL. This will
- // be handled by the throttler as if an HTTP 503 response had been received to
- // the request, i.e. it will count as a failure, unless the HTTP response code
- // indicated is already one of those that will be counted as an error.
- void ReceivedContentWasMalformed(int response_code);
- // Get the URL ID associated with this entry. Should only be used for
- // debugging purpose.
- const std::string& GetURLIdForDebugging() const;
- protected:
- void Initialize();
- // Returns true if the given response code is considered a success for
- // throttling purposes.
- bool IsConsideredSuccess(int response_code);
- // Equivalent to TimeTicks::Now(), virtual to be mockable for testing purpose.
- virtual base::TimeTicks ImplGetTimeNow() const;
- // Retrieves the back-off entry object we're using. Used to enable a
- // unit testing seam for dependency injection in tests.
- virtual const net::BackoffEntry* GetBackoffEntry() const;
- virtual net::BackoffEntry* GetBackoffEntry();
- // Used by tests.
- base::TimeTicks sliding_window_release_time() const {
- return sliding_window_release_time_;
- }
- // Used by tests.
- void set_sliding_window_release_time(const base::TimeTicks& release_time) {
- sliding_window_release_time_ = release_time;
- }
- // Valid and immutable after construction time.
- net::BackoffEntry::Policy backoff_policy_;
- private:
- // Timestamp calculated by the sliding window algorithm for when we advise
- // clients the next request should be made, at the earliest. Advisory only,
- // not used to deny requests.
- base::TimeTicks sliding_window_release_time_;
- // A list of the recent send events. We use them to decide whether there are
- // too many requests sent in sliding window.
- base::queue<base::TimeTicks> send_log_;
- 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.
- net::BackoffEntry backoff_entry_;
- // Canonicalized URL string that this entry is for; used for logging only.
- const std::string url_id_;
- };
- } // namespace extensions
- #endif // EXTENSIONS_RENDERER_EXTENSION_THROTTLE_ENTRY_H_
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