components/policy/core/common/cloud/rate_limiter.h

   1 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
   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 COMPONENTS_POLICY_CORE_COMMON_CLOUD_RATE_LIMITER_H_
   6 #define COMPONENTS_POLICY_CORE_COMMON_CLOUD_RATE_LIMITER_H_
   7
   8 #include <queue>
   9
  10 #include "base/basictypes.h"
  11 #include "base/callback.h"
  12 #include "base/cancelable_callback.h"
  13 #include "base/memory/ref_counted.h"
  14 #include "base/memory/scoped_ptr.h"
  15 #include "base/threading/non_thread_safe.h"
  16 #include "base/time/time.h"
  17 #include "components/policy/policy_export.h"
  18
  19 namespace base {
  20 class SequencedTaskRunner;
  21 class TickClock;
  22 }
  23
  24 namespace policy {
  25
  26 // A simple class to limit the rate at which a callback is invoked.
  27 class POLICY_EXPORT RateLimiter : public base::NonThreadSafe {
  28  public:
  29   // Will limit invocations of |callback| to |max_requests| per |duration|.
  30   // |task_runner| is used to post delayed tasks, and |clock| is used to
  31   // measure elapsed time.
  32   RateLimiter(size_t max_requests,
  33               const base::TimeDelta& duration,
  34               const base::Closure& callback,
  35               scoped_refptr<base::SequencedTaskRunner> task_runner,
  36               scoped_ptr<base::TickClock> clock);
  37   ~RateLimiter();
  38
  39   // Posts a request to invoke |callback_|. It is invoked immediately if the
  40   // rate in the preceding |duration_| period is within the limit, otherwise
  41   // the callback will be invoked later, ensuring the allowed rate is not
  42   // exceeded.
  43   void PostRequest();
  44
  45  private:
  46   const size_t max_requests_;
  47   const base::TimeDelta duration_;
  48   base::Closure callback_;
  49   scoped_refptr<base::SequencedTaskRunner> task_runner_;
  50   scoped_ptr<base::TickClock> clock_;
  51
  52   std::queue<base::TimeTicks> invocation_times_;
  53   base::CancelableClosure delayed_callback_;
  54
  55   DISALLOW_COPY_AND_ASSIGN(RateLimiter);
  56 };
  57
  58 }  // namespace policy
  59
  60 #endif  // COMPONENTS_POLICY_CORE_COMMON_CLOUD_RATE_LIMITER_H_