Make variable naming and gflags more standardized and easier to understand

src/brpc/policy/auto_concurrency_limiter.cpp

@@ -22,36 +22,35 @@
 namespace brpc {
 namespace policy {
 
-DEFINE_int32(auto_cl_peak_qps_window_size, 50, 
-             "The number of samples windows used for peak-qps calculations.");
-DEFINE_double(auto_cl_sampling_interval_ms, 0.1, 
-             "Interval for sampling request in auto concurrency limiter");
-DEFINE_int32(auto_cl_sample_window_size_ms, 1000,
-             "Sample window size for update max concurrency in grandient "
-             "concurrency limiter");
+DEFINE_int32(auto_cl_sample_window_size_ms, 1000, "Duration of the sampling window.");
 DEFINE_int32(auto_cl_min_sample_count, 100,
-             "Minimum sample count for update max concurrency");
+             "During the duration of the sampling window, if the number of "
+             "requests collected is less than this value, the sampling window "
+             "will be discarded.");
 DEFINE_int32(auto_cl_max_sample_count, 500,
-             "Maximum sample count for update max concurrency");
+             "During the duration of the sampling window, once the number of "
+             "requests collected is greater than this value, even if the "
+             "duration of the window has not ended, the max_concurrency will "
+             "be updated and a new sampling window will be started.");
 DEFINE_int32(auto_cl_initial_max_concurrency, 40,
              "Initial max concurrency for grandient concurrency limiter");
-DEFINE_int32(auto_cl_reset_interval_ms, 50000, 
-             "Interval for remeasurement of noload_latency. The period of "
+DEFINE_int32(auto_cl_noload_latency_remeasure_interval_ms, 50000, 
+             "Interval for remeasurement of noload_latency. In the period of "
              "remeasurement of noload_latency will halve max_concurrency.");
-DEFINE_int32(auto_cl_reset_duration_ms, 2000, 
-             "The duration of the remeasurement of noload_latency.");
-DEFINE_int32(auto_cl_min_concurrency, 40, "Minimum value of max_concurrency");
-
-DEFINE_double(auto_cl_adjust_smooth, 0.9,
-              "Smooth coefficient for adjust the max concurrency, the value "
-              "is 0-1, the larger the value, the smaller the amount of each "
-              "change");
+DEFINE_int32(auto_cl_noload_latency_remeasure_period_ms, 2000, 
+             "The duration of the remeasurement of noload_latency.Note that "
+             "in the period of remeasurement, max_concurrency will be halved");
+DEFINE_double(auto_cl_sampling_interval_ms, 0.1, 
+             "Interval for sampling request in auto concurrency limiter");
+DEFINE_double(auto_cl_alpha_factor_for_ema, 0.1,
+              "The smoothing coefficient used in the calculation of ema, "
+              "the value range is 0-1. The smaller the value, the smaller "
+              "the effect of a single sample_window on max_concurrency.");
 DEFINE_double(auto_cl_fail_punish_ratio, 1.0,
               "Use the failed requests to punish normal requests. The larger "
               "the configuration item, the more aggressive the penalty strategy.");
-DEFINE_double(auto_cl_overload_threshold, 0.40, 
+DEFINE_double(auto_cl_overload_threshold, 0.3, 
               "Expected ratio of latency fluctuations");
-
 DEFINE_bool(auto_cl_enable_error_punish, true,
             "Whether to consider failed requests when calculating maximum concurrency");
 
@@ -60,12 +59,11 @@ static int32_t cast_max_concurrency(void* arg) {
 }
 
 AutoConcurrencyLimiter::AutoConcurrencyLimiter()
-    : _reset_start_us(NextResetTime())
+    : _reset_start_us(NextResetTime(butil::gettimeofday_us()))
     , _reset_end_us(0)
     , _min_latency_us(-1)
     , _ema_peak_qps(-1)
-    , _qps_bq(FLAGS_auto_cl_peak_qps_window_size)
-    , _smooth(FLAGS_auto_cl_adjust_smooth)
+    , _ema_factor(FLAGS_auto_cl_alpha_factor_for_ema)
     , _overload_threshold(FLAGS_auto_cl_overload_threshold)
     , _max_concurrency_bvar(cast_max_concurrency, &_max_concurrency)
     , _last_sampling_time_us(0)
@@ -127,10 +125,10 @@ void AutoConcurrencyLimiter::OnResponded(int error_code, int64_t latency_us) {
     }
 }
 
-int64_t AutoConcurrencyLimiter::NextResetTime() {
-    int64_t reset_start_us = butil::gettimeofday_us() + 
-        (FLAGS_auto_cl_reset_interval_ms / 2 + 
-         butil::fast_rand_less_than(FLAGS_auto_cl_reset_interval_ms / 2)) * 1000;
+int64_t AutoConcurrencyLimiter::NextResetTime(int64_t sampling_time_us) {
+    int64_t reset_start_us = sampling_time_us + 
+        (FLAGS_auto_cl_noload_latency_remeasure_interval_ms / 2 + 
+         butil::fast_rand_less_than(FLAGS_auto_cl_noload_latency_remeasure_interval_ms / 2)) * 1000;
     return reset_start_us;
 }
 
@@ -185,24 +183,29 @@ void AutoConcurrencyLimiter::UpdateMinLatency(int64_t latency_us) {
     if (_min_latency_us <= 0) {
         _min_latency_us = latency_us;
     } else if (latency_us < _min_latency_us) {
-        _min_latency_us = _min_latency_us * _smooth + latency_us * (1 - _smooth);
+        _min_latency_us = latency_us * _ema_factor + _min_latency_us * (1 - _ema_factor);
     }
 }
 
 void AutoConcurrencyLimiter::UpdateQps(int32_t succ_count, 
                                        int64_t sampling_time_us) {
+    while (!_qps_deque.empty() && 
+           sampling_time_us - _qps_deque.front().first >= 
+               FLAGS_auto_cl_noload_latency_remeasure_interval_ms * 1000) {
+        _qps_deque.pop_front();
+    }
+
     double qps = 1000000.0 * succ_count / (sampling_time_us - _sw.start_time_us);
-    _qps_bq.elim_push(qps);
-    double peak_qps = *(_qps_bq.bottom());
+    _qps_deque.push_back(std::make_pair(sampling_time_us, qps));
+    double peak_qps = 0;
     
-    for (size_t i = 0; i < _qps_bq.size(); ++i) {
-        peak_qps = std::max(*(_qps_bq.bottom(i)), peak_qps);
+    for (auto history_qps : _qps_deque) {
+        peak_qps = std::max(peak_qps, history_qps.second);
     }
-
     if (peak_qps >= _ema_peak_qps) {
         _ema_peak_qps = peak_qps;
     } else {
-        _ema_peak_qps = _ema_peak_qps * _smooth + peak_qps * (1 - _smooth);
+        _ema_peak_qps = peak_qps * _ema_factor + _ema_peak_qps * (1 - _ema_factor);
     }
 }
 
@@ -223,8 +226,8 @@ int32_t AutoConcurrencyLimiter::UpdateMaxConcurrency(int64_t sampling_time_us) {
     int next_max_concurrency = 0;
     if (_reset_start_us <= sampling_time_us) {
         _min_latency_us = -1;
-        _reset_start_us = NextResetTime();
-        _reset_end_us = sampling_time_us + FLAGS_auto_cl_reset_duration_ms * 1000;
+        _reset_start_us = NextResetTime(sampling_time_us);
+        _reset_end_us = sampling_time_us + FLAGS_auto_cl_noload_latency_remeasure_period_ms * 1000;
         next_max_concurrency = _max_concurrency / 2;
     } else {
         int32_t noload_concurrency = 
@@ -236,8 +239,6 @@ int32_t AutoConcurrencyLimiter::UpdateMaxConcurrency(int64_t sampling_time_us) {
             next_max_concurrency = noload_concurrency;
         }
     }
-    next_max_concurrency = 
-        std::max(next_max_concurrency, FLAGS_auto_cl_min_concurrency);
 
     if (next_max_concurrency != _max_concurrency) {
         _max_concurrency = next_max_concurrency;

src/brpc/policy/auto_concurrency_limiter.h

@@ -51,7 +51,7 @@ private:
     };
 
     int32_t AddSample(int error_code, int64_t latency_us, int64_t sampling_time_us);
-    int64_t NextResetTime();
+    int64_t NextResetTime(int64_t sampling_time_us);
 
     // The following methods are not thread safe and can only be called 
     // in AppSample()
@@ -66,9 +66,9 @@ private:
     int64_t _reset_end_us;
     int64_t _min_latency_us;
     double _ema_peak_qps;
-    butil::BoundedQueue<double> _qps_bq;
+    std::deque<std::pair<int64_t, double>> _qps_deque;
 
-    const double _smooth;
+    const double _ema_factor;
     const double _overload_threshold;
 
     butil::Mutex _sw_mutex;