ClickHouse/dbms/src/Common/MemoryTracker.h

#pragma once

#include <atomic>
#include <common/Types.h>
#include <Common/CurrentMetrics.h>
#include <Common/SimpleActionBlocker.h>
#include <Common/VariableContext.h>


/** Tracks memory consumption.
  * It throws an exception if amount of consumed memory become greater than certain limit.
  * The same memory tracker could be simultaneously used in different threads.
  */
class MemoryTracker
{
    std::atomic<Int64> amount {0};
    std::atomic<Int64> peak {0};
    std::atomic<Int64> limit {0};

    /// To test exception safety of calling code, memory tracker throws an exception on each memory allocation with specified probability.
    double fault_probability = 0;

    /// Singly-linked list. All information will be passed to subsequent memory trackers also (it allows to implement trackers hierarchy).
    /// In terms of tree nodes it is the list of parents. Lifetime of these trackers should "include" lifetime of current tracker.
    std::atomic<MemoryTracker *> parent {};

    /// You could specify custom metric to track memory usage.
    CurrentMetrics::Metric metric = CurrentMetrics::end();

    /// This description will be used as prefix into log messages (if isn't nullptr)
    const char * description = nullptr;

public:
    MemoryTracker(VariableContext level = VariableContext::Thread) : level(level) {}
    MemoryTracker(Int64 limit_, VariableContext level = VariableContext::Thread) : limit(limit_), level(level) {}
    MemoryTracker(MemoryTracker * parent_, VariableContext level = VariableContext::Thread) : parent(parent_), level(level) {}

    ~MemoryTracker();

    VariableContext level;

    /** Call the following functions before calling of corresponding operations with memory allocators.
      */
    void alloc(Int64 size);

    void realloc(Int64 old_size, Int64 new_size)
    {
        alloc(new_size - old_size);
    }

    /** This function should be called after memory deallocation.
      */
    void free(Int64 size);

    Int64 get() const
    {
        return amount.load(std::memory_order_relaxed);
    }

    Int64 getPeak() const
    {
        return peak.load(std::memory_order_relaxed);
    }

    void setLimit(Int64 limit_)
    {
        limit.store(limit_, std::memory_order_relaxed);
    }

    /** Set limit if it was not set.
      * Otherwise, set limit to new value, if new value is greater than previous limit.
      */
    void setOrRaiseLimit(Int64 value);

    void setFaultProbability(double value)
    {
        fault_probability = value;
    }

    /// next should be changed only once: from nullptr to some value.
    /// NOTE: It is not true in MergeListElement
    void setParent(MemoryTracker * elem)
    {
        parent.store(elem, std::memory_order_relaxed);
    }

    MemoryTracker * getParent()
    {
        return parent.load(std::memory_order_relaxed);
    }

    /// The memory consumption could be shown in realtime via CurrentMetrics counter
    void setMetric(CurrentMetrics::Metric metric_)
    {
        metric = metric_;
    }

    void setDescription(const char * description_)
    {
        description = description_;
    }

    /// Reset the accumulated data
    void resetCounters();

    /// Reset the accumulated data and the parent.
    void reset();

    /// Prints info about peak memory consumption into log.
    void logPeakMemoryUsage() const;

    /// To be able to temporarily stop memory tracker
    DB::SimpleActionBlocker blocker;
};


/// Convenience methods, that use current thread's memory_tracker if it is available.
namespace CurrentMemoryTracker
{
    void alloc(Int64 size);
    void realloc(Int64 old_size, Int64 new_size);
    void free(Int64 size);
}


DB::SimpleActionLock getCurrentMemoryTrackerActionLock();