time: add more methods to support dynamic rate throttling

 * Allow RateLimiter to change rate after construction.
 * Check range of rate argument in constructor.
 * Atomic increment for RateEstimator.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

diff --git a/include/crucible/time.h b/include/crucible/time.h
index cad7fe35110ce662ad4324a03a59589fc5f8edb6..5aa195f68472c8d896d60ddb14e48a26d4a2b4a2 100644 (file)
--- a/include/crucible/time.h
+++ b/include/crucible/time.h
@@ -34,7 +34,7 @@ namespace crucible {
                double  m_rate;
                double  m_burst;
                double  m_tokens = 0.0;
-               mutex   m_mutex;
+               mutable mutex m_mutex;
 
                void update_tokens();
                RateLimiter() = delete;
@@ -45,6 +45,8 @@ namespace crucible {
                double sleep_time(double cost = 1.0);
                bool is_ready();
                void borrow(double cost = 1.0);
+               void rate(double new_rate);
+               double rate() const;
        };
 
        class RateEstimator {
@@ -88,6 +90,9 @@ namespace crucible {
                // Read count
                uint64_t count() const;
 
+               /// Increment count (like update(count() + more), but atomic)
+               void increment(uint64_t more = 1);
+
                // Convert counts to chrono types
                chrono::high_resolution_clock::time_point time_point(uint64_t absolute_count) const;
                chrono::duration<double> duration(uint64_t relative_count) const;

diff --git a/lib/time.cc b/lib/time.cc
index 99001b6b49bb9ceabe78f3c49e00acd88eb90c9a..4f991e55a7429db4199e87c445910bd6f5f7b404 100644 (file)
--- a/lib/time.cc
+++ b/lib/time.cc
@@ -98,12 +98,16 @@ namespace crucible {
                m_rate(rate),
                m_burst(burst)
        {
+               THROW_CHECK1(invalid_argument, m_rate, m_rate > 0);
+               THROW_CHECK1(invalid_argument, m_burst, m_burst >= 0);
        }
 
        RateLimiter::RateLimiter(double rate) :
                m_rate(rate),
                m_burst(rate)
        {
+               THROW_CHECK1(invalid_argument, m_rate, m_rate > 0);
+               THROW_CHECK1(invalid_argument, m_burst, m_burst >= 0);
        }
 
        void
@@ -119,6 +123,7 @@ namespace crucible {
        double
        RateLimiter::sleep_time(double cost)
        {
+               THROW_CHECK1(invalid_argument, m_rate, m_rate > 0);
                borrow(cost);
                unique_lock<mutex> lock(m_mutex);
                update_tokens();
@@ -154,6 +159,21 @@ namespace crucible {
                m_tokens -= cost;
        }
 
+       void
+       RateLimiter::rate(double const new_rate)
+       {
+               THROW_CHECK1(invalid_argument, new_rate, new_rate > 0);
+               unique_lock<mutex> lock(m_mutex);
+               m_rate = new_rate;
+       }
+
+       double
+       RateLimiter::rate() const
+       {
+               unique_lock<mutex> lock(m_mutex);
+               return m_rate;
+       }
+
        RateEstimator::RateEstimator(double min_delay, double max_delay) :
                m_min_delay(min_delay),
                m_max_delay(max_delay)
@@ -202,6 +222,13 @@ namespace crucible {
                }
        }
 
+       void
+       RateEstimator::increment(const uint64_t more)
+       {
+               unique_lock<mutex> lock(m_mutex);
+               return update_unlocked(m_last_count + more);
+       }
+
        uint64_t
        RateEstimator::count() const
        {