ydb/yql/essentials/utils/log/context.h

#pragma once

#include <util/system/defaults.h>
#include <util/generic/strbuf.h>
#include <util/stream/output.h>
#include <util/system/src_location.h>
#include <util/system/yassert.h>
#include <array>

// continues existing contexts chain

#define YQL_LOG_CTX_SCOPE(...)  \
    auto Y_CAT(c, __LINE__) = ::NYql::NLog::MakeCtx(__VA_ARGS__); \
    Y_UNUSED(Y_CAT(c, __LINE__))

#define YQL_LOG_CTX_BLOCK(...) \
    if (auto Y_GENERATE_UNIQUE_ID(c) = ::NYql::NLog::MakeCtx(__VA_ARGS__)) { \
        goto Y_CAT(YQL_LOG_CTX_LABEL, __LINE__); \
    } else Y_CAT(YQL_LOG_CTX_LABEL, __LINE__):


// starts new contexts chain, after leaving current scope restores
// previous contexts chain

#define YQL_LOG_CTX_ROOT_SESSION_SCOPE(sessionId, ...) \
    auto Y_CAT(c, __LINE__) = ::NYql::NLog::MakeRootCtx(sessionId, ##__VA_ARGS__); \
    Y_UNUSED(Y_CAT(c, __LINE__))

#define YQL_LOG_CTX_ROOT_SCOPE(...)  \
    auto Y_CAT(c, __LINE__) = ::NYql::NLog::MakeRootCtx("", __VA_ARGS__); \
    Y_UNUSED(Y_CAT(c, __LINE__))

#define YQL_LOG_CTX_ROOT_BLOCK(...) \
    if (auto Y_GENERATE_UNIQUE_ID(c) = ::NYql::NLog::MakeRootCtx(__VA_ARGS__)) { \
        goto Y_CAT(YQL_LOG_CTX_LABEL, __LINE__); \
    } else Y_CAT(YQL_LOG_CTX_LABEL, __LINE__):


// adds current contexts path to exception message before throwing it

#define YQL_LOG_CTX_THROW throw ::NYql::NLog::TYqlLogContextLocation(__LOCATION__) +

class TLogElement;

namespace NYql {
namespace NLog {
namespace NImpl {

/**
 * @brief Represents item of logging context list.
 */
class TLogContextListItem {
public:
    TLogContextListItem* Next;
    TLogContextListItem* Prev;
    size_t NamesCount;

    explicit TLogContextListItem(size_t namesCount = 0, size_t headerSize = 0)
        : Next(this)
        , Prev(this)
        , NamesCount(namesCount)
        , HeaderSize_(headerSize)
    {
        // initialize HeaderSize_ if child didn't
        if (headerSize == 0) {
            HeaderSize_ = sizeof(*this);
        }
    }

    virtual ~TLogContextListItem() {
    }

    const TString* begin() const {
        auto* ptr = reinterpret_cast<const ui8*>(this);
        return reinterpret_cast<const TString*>(ptr + HeaderSize_);
    }

    const TString* end() const {
        return begin() + NamesCount;
    }

    bool HasNext() const {
        return Next != this;
    }

    void LinkBefore(TLogContextListItem* item) {
        Y_DEBUG_ABORT_UNLESS(!HasNext());
        Next = item;
        Prev = item->Prev;
        Prev->Next = this;
        Next->Prev = this;
    }

    void Unlink() {
        if (!HasNext()) return;

        Prev->Next = Next;
        Next->Prev = Prev;
        Next = Prev = this;
    }

private:
    // Additional memory before Names_ used in child class 
    size_t HeaderSize_;
};

/**
 * @brief Returns pointer to thread local log context list.
 */
TLogContextListItem* GetLogContextList();

/**
 * @brief Context element with stored SessionId.
*/
class TLogContextSessionItem : public TLogContextListItem {
public:
    TLogContextSessionItem(size_t size, bool hasSessionId_)
        :  TLogContextListItem(size, sizeof(*this)) {
        HasSessionId_ = hasSessionId_;
    }

    bool HasSessionId() const {
        return HasSessionId_;
    }

private:
    bool HasSessionId_;
};

} // namspace NImpl

/**
 * @brief YQL logger context element. Each element can contains several names.
 */
template <size_t Size>
class TLogContext: public NImpl::TLogContextListItem {
public:
    template <typename... TArgs>
    TLogContext(TArgs... args)
        : TLogContextListItem(Size)
        , Names_{{ TString{std::forward<TArgs>(args)}... }}
    {
        LinkBefore(NImpl::GetLogContextList());
    }

    ~TLogContext() {
        Unlink();
    }

    explicit inline operator bool() const noexcept {
        return true;
    }

private:
    std::array<TString, Size> Names_;
};

/**
 * @brief Special Root context elements which replaces previous log context
 *        list head by itself and restores previous one on destruction.
 */
template <size_t Size>
class TRootLogContext: public NImpl::TLogContextSessionItem {
public:
    template <typename... TArgs>
    TRootLogContext(const TString& sessionId, TArgs... args)
        : TLogContextSessionItem(Size, !sessionId.empty())
        , Names_{{ sessionId, TString{std::forward<TArgs>(args)}... }}
    {
        NImpl::TLogContextListItem* ctxList = NImpl::GetLogContextList();
        PrevLogContextHead_.Prev = ctxList->Prev;
        PrevLogContextHead_.Next = ctxList->Next;
        ctxList->Next = ctxList->Prev = ctxList;
        LinkBefore(ctxList);
    }

    ~TRootLogContext() {
        Unlink();
        NImpl::TLogContextListItem* ctxList = NImpl::GetLogContextList();
        ctxList->Prev = PrevLogContextHead_.Prev;
        ctxList->Next = PrevLogContextHead_.Next;
    }

    explicit inline operator bool() const noexcept {
        return true;
    }

private:
    std::array<TString, Size> Names_;
    NImpl::TLogContextListItem PrevLogContextHead_;
};

/**
 * @brief Helper function to construct TLogContext from variable
 *        arguments list.
 */
template <typename... TArgs>
inline auto MakeCtx(TArgs&&... args) -> TLogContext<sizeof...(args)> {
    return TLogContext<sizeof...(args)>(std::forward<TArgs>(args)...);
}

template <typename... TArgs>
inline auto MakeRootCtx(const TString& sessionId, TArgs&&... args) -> TRootLogContext<sizeof...(args) + 1> {
    return TRootLogContext<sizeof...(args) + 1>(sessionId, std::forward<TArgs>(args)...);
}

inline auto MakeRootCtx(const std::pair<TString, TString>& ctx) -> TRootLogContext<2> {
    return TRootLogContext<2>(ctx.first, ctx.second);
}

/**
 * @brief Returns pair with sessionId and
 *        current logger contexts path as string. Each element
 *        is separated with '/'.
 */
std::pair<TString, TString> CurrentLogContextPath();

/**
 * @brief If last throwing exception was performed with YQL_LOG_CTX_THROW
 *        macro this function returns location and context of that throw point.
 */
TString ThrowedLogContextPath();

/**
 * @brief Adds context preffix before logging message.
 */
struct TContextPreprocessor {
    static TAutoPtr<TLogElement> Preprocess(TAutoPtr<TLogElement> element);
};

/**
 * @brief Outputs current logger context into stream
 */
void OutputLogCtx(IOutputStream* out, bool withBraces, bool skipSessionId = false);

/**
 * @brief Outputs current logger context into exception message.
 */
class TYqlLogContextLocation {
public:
    TYqlLogContextLocation(const TSourceLocation& location)
        : Location_(location.File, location.Line)
    {
    }

    void SetThrowedLogContextPath() const;

    template <class T>
    inline T&& operator+(T&& t) {
        SetThrowedLogContextPath();
        return std::forward<T>(t);
    }

private:
    TSourceLocation Location_;
};

} // namespace NLog
} // namespace NYql