ClickHouse/dbms/src/Interpreters/ExternalLoader.h

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#pragma once
#include <common/logger_useful.h>
#include <Poco/Event.h>
#include <mutex>
#include <thread>
#include <unordered_map>
#include <unordered_set>
#include <chrono>
#include <tuple>
#include <Interpreters/IExternalLoadable.h>
#include <Interpreters/IExternalLoaderConfigRepository.h>
#include <Core/Types.h>
#include <pcg_random.hpp>
#include <Common/randomSeed.h>
#include <Common/ThreadPool.h>
namespace DB
{
struct ExternalLoaderUpdateSettings
{
UInt64 check_period_sec = 5;
UInt64 backoff_initial_sec = 5;
/// 10 minutes
UInt64 backoff_max_sec = 10 * 60;
ExternalLoaderUpdateSettings() = default;
ExternalLoaderUpdateSettings(UInt64 check_period_sec, UInt64 backoff_initial_sec, UInt64 backoff_max_sec)
: check_period_sec(check_period_sec),
backoff_initial_sec(backoff_initial_sec),
backoff_max_sec(backoff_max_sec) {}
};
/* External configuration structure.
*
* <external_group>
* <external_config>
* <external_name>name</external_name>
* ....
* </external_config>
* </external_group>
*/
struct ExternalLoaderConfigSettings
{
std::string external_config;
std::string external_name;
std::string path_setting_name;
};
/** Manages user-defined objects.
* Monitors configuration file and automatically reloads objects in a separate thread.
* The monitoring thread wakes up every 'check_period_sec' seconds and checks
* modification time of objects' configuration file. If said time is greater than
* 'config_last_modified', the objects are created from scratch using configuration file,
* possibly overriding currently existing objects with the same name (previous versions of
* overridden objects will live as long as there are any users retaining them).
*
* Apart from checking configuration file for modifications, each object
* has a lifetime of its own and may be updated if it supportUpdates.
* The time of next update is calculated by choosing uniformly a random number
* distributed between lifetime.min_sec and lifetime.max_sec.
* If either of lifetime.min_sec and lifetime.max_sec is zero, such object is never updated.
*/
class ExternalLoader
{
public:
using LoadablePtr = std::shared_ptr<IExternalLoadable>;
private:
struct LoadableInfo final
{
LoadablePtr loadable;
std::string origin;
std::exception_ptr exception;
};
struct FailedLoadableInfo final
{
std::unique_ptr<IExternalLoadable> loadable;
std::chrono::system_clock::time_point next_attempt_time;
UInt64 error_count;
};
public:
using Configuration = Poco::Util::AbstractConfiguration;
using ObjectsMap = std::unordered_map<std::string, LoadableInfo>;
/// Call init() after constructing the instance of any derived class.
ExternalLoader(const Configuration & config_main,
const ExternalLoaderUpdateSettings & update_settings,
const ExternalLoaderConfigSettings & config_settings,
std::unique_ptr<IExternalLoaderConfigRepository> config_repository,
Logger * log, const std::string & loadable_object_name);
virtual ~ExternalLoader();
/// Should be called after creating an instance of a derived class.
/// Loads the objects immediately and starts a separate thread to update them once in each 'reload_period' seconds.
/// This function does nothing if called again.
void init(bool throw_on_error);
/// Forcibly reloads all loadable objects.
void reload();
/// Forcibly reloads specified loadable object.
void reload(const std::string & name);
LoadablePtr getLoadable(const std::string & name) const;
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LoadablePtr tryGetLoadable(const std::string & name) const;
protected:
virtual std::unique_ptr<IExternalLoadable> create(const std::string & name, const Configuration & config,
const std::string & config_prefix) const = 0;
class LockedObjectsMap
{
public:
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LockedObjectsMap(std::mutex & mutex, const ObjectsMap & objects_map) : lock(mutex), objects_map(objects_map) {}
const ObjectsMap & get() { return objects_map; }
private:
std::unique_lock<std::mutex> lock;
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const ObjectsMap & objects_map;
};
/// Direct access to objects.
LockedObjectsMap getObjectsMap() const;
private:
std::once_flag is_initialized_flag;
/// Protects only objects map.
/** Reading and assignment of "loadable" should be done under mutex.
* Creating new versions of "loadable" should not be done under mutex.
*/
mutable std::mutex map_mutex;
/// Protects all data, currently used to avoid races between updating thread and SYSTEM queries.
/// The mutex is recursive because creating of objects might be recursive, i.e.
/// creating objects might cause creating other objects.
mutable std::recursive_mutex all_mutex;
/// name -> loadable.
mutable ObjectsMap loadable_objects;
struct LoadableCreationInfo
{
std::string name;
Poco::AutoPtr<Poco::Util::AbstractConfiguration> config;
std::string config_path;
std::string config_prefix;
};
/// Objects which should be reloaded soon.
mutable std::unordered_map<std::string, LoadableCreationInfo> objects_to_reload;
/// Here are loadable objects, that has been never loaded successfully.
/// They are also in 'loadable_objects', but with nullptr as 'loadable'.
mutable std::unordered_map<std::string, FailedLoadableInfo> failed_loadable_objects;
/// Both for loadable_objects and failed_loadable_objects.
mutable std::unordered_map<std::string, std::chrono::system_clock::time_point> update_times;
std::unordered_map<std::string, std::unordered_set<std::string>> loadable_objects_defined_in_config;
mutable pcg64 rnd_engine{randomSeed()};
const Configuration & config_main;
const ExternalLoaderUpdateSettings & update_settings;
const ExternalLoaderConfigSettings & config_settings;
std::unique_ptr<IExternalLoaderConfigRepository> config_repository;
ThreadFromGlobalPool reloading_thread;
Poco::Event destroy;
Logger * log;
/// Loadable object name to use in log messages.
std::string object_name;
std::unordered_map<std::string, Poco::Timestamp> last_modification_times;
void initImpl(bool throw_on_error);
/// Check objects definitions in config files and reload or/and add new ones if the definition is changed
/// If loadable_name is not empty, load only loadable object with name loadable_name
void reloadFromConfigFiles(bool throw_on_error, bool force_reload = false, const std::string & loadable_name = "");
void reloadFromConfigFile(const std::string & config_path, const bool force_reload, const std::string & loadable_name);
/// Check config files and update expired loadable objects
void reloadAndUpdate(bool throw_on_error = false);
void reloadPeriodically();
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void finishReload(const std::string & loadable_name, bool throw_on_error) const;
void finishAllReloads(bool throw_on_error) const;
void finishReloadImpl(const LoadableCreationInfo & creation_info, bool throw_on_error) const;
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LoadablePtr getLoadableImpl(const std::string & name, bool throw_on_error) const;
};
}