ClickHouse/dbms/src/Storages/MergeTree/BackgroundProcessingPool.cpp

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#include <Common/Exception.h>
#include <Common/setThreadName.h>
#include <Common/CurrentMetrics.h>
#include <Common/MemoryTracker.h>
#include <Common/randomSeed.h>
#include <IO/WriteHelpers.h>
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#include <common/logger_useful.h>
#include <Storages/MergeTree/BackgroundProcessingPool.h>
#include <pcg_random.hpp>
#include <random>
namespace CurrentMetrics
{
extern const Metric BackgroundPoolTask;
extern const Metric MemoryTrackingInBackgroundProcessingPool;
}
namespace DB
{
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constexpr double BackgroundProcessingPool::sleep_seconds;
constexpr double BackgroundProcessingPool::sleep_seconds_random_part;
void BackgroundProcessingPool::TaskInfo::wake()
{
if (removed)
return;
Poco::Timestamp current_time;
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{
std::unique_lock<std::mutex> lock(pool.tasks_mutex);
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auto next_time_to_execute = iterator->first;
TaskHandle this_task_handle = iterator->second;
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/// If this task was done nothing at previous time and it has to sleep, then cancel sleep time.
if (next_time_to_execute > current_time)
next_time_to_execute = current_time;
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pool.tasks.erase(iterator);
iterator = pool.tasks.emplace(next_time_to_execute, this_task_handle);
}
/// Note that if all threads are currently do some work, this call will not wakeup any thread.
pool.wake_event.notify_one();
}
BackgroundProcessingPool::BackgroundProcessingPool(int size_) : size(size_)
{
LOG_INFO(&Logger::get("BackgroundProcessingPool"), "Create BackgroundProcessingPool with " << size << " threads");
threads.resize(size);
for (auto & thread : threads)
thread = std::thread([this] { threadFunction(); });
}
BackgroundProcessingPool::TaskHandle BackgroundProcessingPool::addTask(const Task & task)
{
TaskHandle res = std::make_shared<TaskInfo>(*this, task);
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Poco::Timestamp current_time;
{
std::unique_lock<std::mutex> lock(tasks_mutex);
res->iterator = tasks.emplace(current_time, res);
}
wake_event.notify_all();
return res;
}
void BackgroundProcessingPool::removeTask(const TaskHandle & task)
{
if (task->removed.exchange(true))
return;
/// Wait for all executions of this task.
{
std::unique_lock<std::shared_mutex> wlock(task->rwlock);
}
{
std::unique_lock<std::mutex> lock(tasks_mutex);
tasks.erase(task->iterator);
}
}
BackgroundProcessingPool::~BackgroundProcessingPool()
{
try
{
shutdown = true;
wake_event.notify_all();
for (std::thread & thread : threads)
thread.join();
}
catch (...)
{
tryLogCurrentException(__PRETTY_FUNCTION__);
}
}
void BackgroundProcessingPool::threadFunction()
{
setThreadName("BackgrProcPool");
MemoryTracker memory_tracker;
memory_tracker.setMetric(CurrentMetrics::MemoryTrackingInBackgroundProcessingPool);
current_memory_tracker = &memory_tracker;
pcg64 rng(randomSeed());
std::this_thread::sleep_for(std::chrono::duration<double>(std::uniform_real_distribution<double>(0, sleep_seconds_random_part)(rng)));
while (!shutdown)
{
bool done_work = false;
TaskHandle task;
try
{
Poco::Timestamp min_time;
{
std::unique_lock<std::mutex> lock(tasks_mutex);
if (!tasks.empty())
{
for (const auto & time_handle : tasks)
{
if (!time_handle.second->removed)
{
min_time = time_handle.first;
task = time_handle.second;
break;
}
}
}
}
if (shutdown)
break;
if (!task)
{
std::unique_lock<std::mutex> lock(tasks_mutex);
wake_event.wait_for(lock,
std::chrono::duration<double>(sleep_seconds
+ std::uniform_real_distribution<double>(0, sleep_seconds_random_part)(rng)));
continue;
}
/// No tasks ready for execution.
Poco::Timestamp current_time;
if (min_time > current_time)
{
std::unique_lock<std::mutex> lock(tasks_mutex);
wake_event.wait_for(lock, std::chrono::microseconds(
min_time - current_time + std::uniform_int_distribution<uint64_t>(0, sleep_seconds_random_part * 1000000)(rng)));
}
std::shared_lock<std::shared_mutex> rlock(task->rwlock);
if (task->removed)
continue;
{
CurrentMetrics::Increment metric_increment{CurrentMetrics::BackgroundPoolTask};
done_work = task->function();
}
}
catch (...)
{
tryLogCurrentException(__PRETTY_FUNCTION__);
}
if (shutdown)
break;
/// If task has done work, it could be executed again immediately.
/// If not, add delay before next run.
Poco::Timestamp next_time_to_execute = Poco::Timestamp() + (done_work ? 0 : sleep_seconds * 1000000);
{
std::unique_lock<std::mutex> lock(tasks_mutex);
if (task->removed)
continue;
tasks.erase(task->iterator);
task->iterator = tasks.emplace(next_time_to_execute, task);
}
}
current_memory_tracker = nullptr;
}
}