libfilezilla
rate_limiter.hpp
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1 #ifndef LIBFILEZILLA_RATE_LIMITER_HEADER
2 #define LIBFILEZILLA_RATE_LIMITER_HEADER
3 
12 #include "event_handler.hpp"
13 
14 #include <atomic>
15 #include <vector>
16 
17 namespace fz {
18 
19 namespace rate {
20 using type = uint64_t;
21 enum : type {
22  unlimited = static_cast<type>(-1)
23 };
24 }
25 
26 namespace direction {
27 enum type : size_t {
28  inbound,
29  outbound
30 };
31 }
32 
33 class rate_limiter;
34 
45 class FZ_PUBLIC_SYMBOL rate_limit_manager final : public event_handler
46 {
47 public:
48  explicit rate_limit_manager(event_loop & loop);
49  virtual ~rate_limit_manager();
50 
57  void add(rate_limiter* limiter);
58 
60  void set_burst_tolerance(rate::type tolerance);
61 
62 private:
63  friend class rate_limiter;
64  friend class bucket_base;
65  friend class bucket;
66 
67  void record_activity();
68 
69  void operator()(event_base const& ev);
70  void on_timer(timer_id const&);
71 
72  void process(rate_limiter* limiter, bool locked);
73 
74  std::atomic<int> activity_{2};
75  mutex mtx_{false};
76  std::vector<rate_limiter*> limiters_;
77 
78  std::atomic<timer_id> timer_{};
79 
80  std::atomic<rate::type> burst_tolerance_{1};
81 };
82 
84 class FZ_PUBLIC_SYMBOL bucket_base
85 {
86 public:
87  virtual ~bucket_base() noexcept = default;
88 
94  virtual void remove_bucket();
95 
96 protected:
97  friend class rate_limiter;
98 
104  virtual void lock_tree() { mtx_.lock(); }
105 
111  virtual void update_stats(bool & active) = 0;
112 
118  virtual size_t weight() const { return 1; }
119 
125  virtual size_t unsaturated(direction::type const /*d*/) const { return 0; }
126 
132  virtual void set_mgr_recursive(rate_limit_manager * mgr);
133 
143  virtual rate::type add_tokens(direction::type const /*d*/, rate::type /*tokens*/, rate::type /*limit*/) = 0;
144 
154  virtual rate::type distribute_overflow(direction::type const /*d*/, rate::type /*tokens*/) { return 0; }
155 
159  virtual void unlock_tree() { mtx_.unlock(); }
160 
166  virtual std::array<rate::type, 2> gather_unspent_for_removal() = 0;
167 
168  mutex mtx_{false};
169  rate_limit_manager * mgr_{};
170  void * parent_{};
171  size_t idx_{static_cast<size_t>(-1)};
172 };
173 
184 class FZ_PUBLIC_SYMBOL rate_limiter final : public bucket_base
185 {
186 public:
187  rate_limiter() = default;
188  explicit rate_limiter(rate_limit_manager * mgr);
189  virtual ~rate_limiter();
190 
197  void add(bucket_base* bucket);
198 
206  void set_limits(rate::type download_limit, rate::type upload_limit);
207 
209  rate::type limit(direction::type const d);
210 
211 private:
212  friend class bucket_base;
213  friend class rate_limit_manager;
214 
215  virtual void lock_tree() override;
216 
217  bool do_set_limit(direction::type const d, rate::type limit);
218 
219  virtual void update_stats(bool & active) override;
220  virtual size_t weight() const override { return weight_; }
221  virtual size_t unsaturated(direction::type const d) const override { return data_[d].unused_capacity_ ? data_[d].unsaturated_ : 0; }
222  virtual void set_mgr_recursive(rate_limit_manager * mgr) override;
223 
224  virtual rate::type add_tokens(direction::type const d, rate::type tokens, rate::type limit) override;
225  virtual rate::type distribute_overflow(direction::type const d, rate::type tokens) override;
226 
227  virtual void unlock_tree() override;
228 
229  void pay_debt(direction::type const d);
230 
231  virtual std::array<rate::type, 2> gather_unspent_for_removal() override;
232 
233  std::vector<bucket_base*> buckets_;
234  std::vector<size_t> scratch_buffer_;
235  size_t weight_{};
236 
237  struct data_t {
238  rate::type limit_{rate::unlimited};
239  rate::type merged_tokens_;
240  rate::type overflow_{};
241  rate::type debt_{};
242  rate::type unused_capacity_{};
243  rate::type carry_{};
244  size_t unsaturated_{};
245  } data_[2];
246 };
247 
251 class FZ_PUBLIC_SYMBOL bucket : public bucket_base
252 {
253 public:
254  virtual ~bucket();
255 
256  virtual void remove_bucket() override;
257 
263  rate::type available(direction::type const d);
264 
271  void consume(direction::type const d, rate::type amount);
272 
273 protected:
279  virtual void wakeup(direction::type /*d*/) {}
280 
282  bool waiting(scoped_lock & l, direction::type d);
283 
284 private:
285  virtual void update_stats(bool & active) override;
286  virtual size_t unsaturated(direction::type const d) const override { return data_[d].unsaturated_ ? 1 : 0; }
287 
288  virtual rate::type add_tokens(direction::type const d, rate::type tokens, rate::type limit) override;
289  virtual rate::type distribute_overflow(direction::type const d, rate::type tokens) override;
290 
291  virtual void unlock_tree() override;
292 
293  virtual std::array<rate::type, 2> gather_unspent_for_removal() override;
294 
295  struct data_t {
296  rate::type available_{rate::unlimited};
297  rate::type overflow_multiplier_{1};
298  rate::type bucket_size_{rate::unlimited};
299  bool waiting_{};
300  bool unsaturated_{};
301  } data_[2];
302 };
303 
304 }
305 
306 #endif
virtual rate::type distribute_overflow(direction::type const , rate::type)
Recursively distributes overflow.
Definition: rate_limiter.hpp:154
Context for rate_limiters.
Definition: rate_limiter.hpp:45
A simple scoped lock.
Definition: mutex.hpp:64
A rate-limited token bucket.
Definition: rate_limiter.hpp:251
Simple handler for asynchronous event processing.
Definition: event_handler.hpp:54
Declares the event_handler class.
virtual void unlock_tree()
Recursively unlocks the mutexes of self and all children.
Definition: rate_limiter.hpp:159
virtual void wakeup(direction::type)
Called in response to unlock_tree if tokens have become available.
Definition: rate_limiter.hpp:279
virtual size_t weight() const
Returns the weight of the tree.
Definition: rate_limiter.hpp:118
A threaded event loop that supports sending events and timers.
Definition: event_loop.hpp:33
A limiter for the attached buckets.
Definition: rate_limiter.hpp:184
Base class for buckets.
Definition: rate_limiter.hpp:84
The namespace used by libfilezilla.
Definition: apply.hpp:17
virtual size_t unsaturated(direction::type const ) const
Returns the number of buckets not yet full.
Definition: rate_limiter.hpp:125
virtual void lock_tree()
Recursively locks the mutexes of self and all children.
Definition: rate_limiter.hpp:104
The process class manages an asynchronous process with redirected IO.
Definition: process.hpp:26
Lean replacement for std::(recursive_)mutex.
Definition: mutex.hpp:27
Common base class for all events.
Definition: event.hpp:22