intermediate changes

ref:cde9a383711a11544ce7e107a78147fb96cc4029

1 files changed, 210 insertions, 0 deletions

diff --git a/library/cpp/monlib/metrics/histogram_snapshot.h b/library/cpp/monlib/metrics/histogram_snapshot.h
new file mode 100644
index 0000000000..e8acf6ac2b
--- /dev/null
+++ b/library/cpp/monlib/metrics/histogram_snapshot.h
@@ -0,0 +1,210 @@
+#pragma once
+
+#include <util/generic/array_ref.h>
+#include <util/generic/ptr.h>
+#include <util/generic/vector.h>
+#include <util/generic/yexception.h>
+
+#include <cmath>
+#include <limits>
+
+
+namespace NMonitoring {
+
+    using TBucketBound = double;
+    using TBucketValue = ui64;
+
+    using TBucketBounds = TVector<TBucketBound>;
+    using TBucketValues = TVector<TBucketValue>;
+
+    constexpr ui32 HISTOGRAM_MAX_BUCKETS_COUNT = 51;
+    constexpr TBucketBound HISTOGRAM_INF_BOUND = std::numeric_limits<TBucketBound>::max();
+
+    ///////////////////////////////////////////////////////////////////////////
+    // IHistogramSnapshot
+    ///////////////////////////////////////////////////////////////////////////
+    class IHistogramSnapshot: public TAtomicRefCount<IHistogramSnapshot> {
+    public:
+        virtual ~IHistogramSnapshot() = default;
+
+        /**
+         * @return buckets count.
+         */
+        virtual ui32 Count() const = 0;
+
+        /**
+         * @return upper bound for the bucket with particular index.
+         */
+        virtual TBucketBound UpperBound(ui32 index) const = 0;
+
+        /**
+         * @return value stored in the bucket with particular index.
+         */
+        virtual TBucketValue Value(ui32 index) const = 0;
+    };
+
+    using IHistogramSnapshotPtr = TIntrusivePtr<IHistogramSnapshot>;
+
+    ///////////////////////////////////////////////////////////////////////////////
+    // TLinearHistogramSnapshot
+    ///////////////////////////////////////////////////////////////////////////////
+    class TLinearHistogramSnapshot: public IHistogramSnapshot {
+    public:
+        TLinearHistogramSnapshot(
+                TBucketBound startValue, TBucketBound bucketWidth, TBucketValues values)
+            : StartValue_(startValue)
+            , BucketWidth_(bucketWidth)
+            , Values_(std::move(values))
+        {
+        }
+
+        ui32 Count() const override {
+            return static_cast<ui32>(Values_.size());
+        }
+
+        TBucketBound UpperBound(ui32 index) const override {
+            Y_ASSERT(index < Values_.size());
+            if (index == Count() - 1) {
+                return Max<TBucketBound>();
+            }
+            return StartValue_ + BucketWidth_ * index;
+        }
+
+        TBucketValue Value(ui32 index) const override {
+            Y_ASSERT(index < Values_.size());
+            return Values_[index];
+        }
+
+        ui64 MemorySizeBytes() {
+            return sizeof(*this) + Values_.capacity() * sizeof(decltype(Values_)::value_type);
+        }
+
+    private:
+        TBucketBound StartValue_;
+        TBucketBound BucketWidth_;
+        TBucketValues Values_;
+    };
+
+    ///////////////////////////////////////////////////////////////////////////
+    // TExponentialHistogramSnapshot
+    ///////////////////////////////////////////////////////////////////////////
+    class TExponentialHistogramSnapshot: public IHistogramSnapshot {
+    public:
+        TExponentialHistogramSnapshot(
+                double base, double scale, TBucketValues values)
+            : Base_(base)
+            , Scale_(scale)
+            , Values_(std::move(values))
+        {
+        }
+
+        ui32 Count() const override {
+            return static_cast<ui32>(Values_.size());
+        }
+
+        TBucketBound UpperBound(ui32 index) const override {
+            Y_ASSERT(index < Values_.size());
+            if (index == Values_.size() - 1) {
+                return Max<TBucketBound>();
+            }
+            return std::round(Scale_ * std::pow(Base_, index));
+        }
+
+        TBucketValue Value(ui32 index) const override {
+            Y_ASSERT(index < Values_.size());
+            return Values_[index];
+        }
+
+        ui64 MemorySizeBytes() {
+            return sizeof(*this) + Values_.capacity() * sizeof(decltype(Values_)::value_type);
+        }
+
+    private:
+        double Base_;
+        double Scale_;
+        TBucketValues Values_;
+    };
+
+    using TBucket = std::pair<TBucketBound, TBucketValue>;
+
+    ///////////////////////////////////////////////////////////////////////
+    // TExplicitHistogramSnapshot
+    ///////////////////////////////////////////////////////////////////////
+    //
+    // Memory layout (single contiguous block):
+    //
+    //  +------+-----------+--------------+--------+--------+-       -+--------+--------+
+    //  | vptr | RefsCount | BucketsCount | Bound1 | Value1 |   ...   | BoundN | ValueN |
+    //  +------+-----------+--------------+--------+--------+-       -+--------+--------+
+    //
+    class TExplicitHistogramSnapshot: public IHistogramSnapshot, private TNonCopyable {
+    public:
+        static TIntrusivePtr<TExplicitHistogramSnapshot> New(ui32 bucketsCount) {
+            size_t bucketsSize = bucketsCount * sizeof(TBucket);
+            Y_ENSURE(bucketsCount <= HISTOGRAM_MAX_BUCKETS_COUNT, "Cannot allocate a histogram with " << bucketsCount
+                << " buckets. Bucket count is limited to " << HISTOGRAM_MAX_BUCKETS_COUNT);
+
+            return new(bucketsSize) TExplicitHistogramSnapshot(bucketsCount);
+        }
+
+        TBucket& operator[](ui32 index) noexcept {
+            return Bucket(index);
+        }
+
+        ui32 Count() const override {
+            return BucketsCount_;
+        }
+
+        TBucketBound UpperBound(ui32 index) const override {
+            return Bucket(index).first;
+        }
+
+        TBucketValue Value(ui32 index) const override {
+            return Bucket(index).second;
+        }
+
+        ui64 MemorySizeBytes() const {
+            return sizeof(*this) + BucketsCount_ * sizeof(TBucket);
+        }
+
+    private:
+        explicit TExplicitHistogramSnapshot(ui32 bucketsCount) noexcept
+            : BucketsCount_(bucketsCount)
+        {
+        }
+
+        static void* operator new(size_t size, size_t bucketsSize) {
+            return ::operator new(size + bucketsSize);
+        }
+
+        static void operator delete(void* mem) {
+            ::operator delete(mem);
+        }
+
+        static void operator delete(void* mem, size_t, size_t) {
+            // this operator can be called as paired for custom new operator
+            ::operator delete(mem);
+        }
+
+        TBucket& Bucket(ui32 index) noexcept {
+            Y_VERIFY_DEBUG(index < BucketsCount_);
+            return *(reinterpret_cast<TBucket*>(this + 1) + index);
+        }
+
+        const TBucket& Bucket(ui32 index) const noexcept {
+            Y_VERIFY_DEBUG(index < BucketsCount_);
+            return *(reinterpret_cast<const TBucket*>(this + 1) + index);
+        }
+
+    private:
+        ui32 BucketsCount_;
+    };
+
+    static_assert(alignof(TExplicitHistogramSnapshot) == alignof(TBucket),
+                  "mismatched alingments of THistogramSnapshot and TBucket");
+
+    IHistogramSnapshotPtr ExplicitHistogramSnapshot(TConstArrayRef<TBucketBound> bounds, TConstArrayRef<TBucketValue> values);
+
+} // namespace NMonitoring
+
+std::ostream& operator<<(std::ostream& os, const NMonitoring::IHistogramSnapshot& hist);