ceph/src/jaegertracing/jaeger-client-cpp/src/jaegertracing/samplers/ProbabilisticSampler.h

   1 /*
   2  * Copyright (c) 2017 Uber Technologies, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #ifndef JAEGERTRACING_SAMPLERS_PROBABILISTICSAMPLER_H
  18 #define JAEGERTRACING_SAMPLERS_PROBABILISTICSAMPLER_H
  19
  20 #include "jaegertracing/Compilers.h"
  21
  22 #include "jaegertracing/Constants.h"
  23 #include "jaegertracing/Tag.h"
  24 #include "jaegertracing/TraceID.h"
  25 #include "jaegertracing/samplers/Sampler.h"
  26 #include "jaegertracing/samplers/SamplingStatus.h"
  27 #include <algorithm>
  28 #include <cstdint>
  29 #include <limits>
  30 #include <string>
  31 #include <vector>
  32
  33 namespace jaegertracing {
  34 namespace samplers {
  35
  36 class ProbabilisticSampler : public Sampler {
  37   public:
  38     explicit ProbabilisticSampler(double samplingRate)
  39         : _samplingRate(std::max(0.0, std::min(samplingRate, 1.0)))
  40         , _samplingBoundary(computeSamplingBoundary(_samplingRate))
  41         , _tags({ { kSamplerTypeTagKey, kSamplerTypeProbabilistic },
  42                   { kSamplerParamTagKey, _samplingRate } })
  43     {
  44     }
  45
  46     double samplingRate() const { return _samplingRate; }
  47
  48     SamplingStatus isSampled(const TraceID& id,
  49                              const std::string& operation) override
  50     {
  51         return SamplingStatus(_samplingBoundary >= id.low(), _tags);
  52     }
  53
  54     void close() override {}
  55
  56     Type type() const override { return Type::kProbabilisticSampler; }
  57
  58   private:
  59     static constexpr auto kMaxRandomNumber =
  60         std::numeric_limits<uint64_t>::max();
  61
  62     double _samplingRate;
  63     uint64_t _samplingBoundary;
  64     std::vector<Tag> _tags;
  65
  66     static uint64_t computeSamplingBoundary(long double samplingRate)
  67     {
  68         const auto maxRandNumber = static_cast<long double>(kMaxRandomNumber);
  69         const auto samplingBoundary = samplingRate * maxRandNumber;
  70
  71         // Protect against overflow in case samplingBoundary rounds
  72         // higher than kMaxRandNumber.
  73         if (samplingBoundary == maxRandNumber) {
  74             return kMaxRandomNumber;
  75         }
  76
  77         return static_cast<uint64_t>(samplingBoundary);
  78     }
  79 };
  80
  81 }  // namespace samplers
  82 }  // namespace jaegertracing
  83
  84 #endif  // JAEGERTRACING_SAMPLERS_PROBABILISTICSAMPLER_H