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#pragma once
#include <string>
#include <memory>
#include <boost/noncopyable.hpp>
#include <pcg_random.hpp>
#include <base/types.h>
namespace Poco::Util
{
class AbstractConfiguration;
}
namespace DB
{
/// Min and max lifetimes for a loadable object or it's entry
struct ExternalLoadableLifetime
{
UInt64 min_sec = 0;
UInt64 max_sec = 0;
ExternalLoadableLifetime(const Poco::Util::AbstractConfiguration & config, const std::string & config_prefix);
ExternalLoadableLifetime() {}
};
/// Get delay before trying to load again after error.
UInt64 calculateDurationWithBackoff(pcg64 & rnd_engine, size_t error_count = 1);
/// Basic interface for external loadable objects. Is used in ExternalLoader.
class IExternalLoadable : public std::enable_shared_from_this<IExternalLoadable>, private boost::noncopyable
{
public:
virtual ~IExternalLoadable() = default;
virtual const ExternalLoadableLifetime & getLifetime() const = 0;
virtual std::string getLoadableName() const = 0;
/// True if object can be updated when lifetime exceeded.
virtual bool supportUpdates() const = 0;
/// If lifetime exceeded and isModified(), ExternalLoader replace current object with the result of clone().
virtual bool isModified() const = 0;
/// Returns new object with the same configuration. Is used to update modified object when lifetime exceeded.
virtual std::shared_ptr<const IExternalLoadable> clone() const = 0;
};
}
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