subscription_token.hpp

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#pragma once
 
/// @file userver/storages/redis/subscription_token.hpp
/// @brief @copybrief storages::redis::SubscriptionToken
 
#include <functional>
#include <memory>
#include <string>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::redis {
 
struct CommandControl;
 
namespace impl {
 
class SubscriptionTokenImplBase {
public:
    SubscriptionTokenImplBase() = default;
 
    SubscriptionTokenImplBase(SubscriptionTokenImplBase&&) = delete;
    SubscriptionTokenImplBase& operator=(SubscriptionTokenImplBase&&) = delete;
 
    SubscriptionTokenImplBase(const SubscriptionTokenImplBase&) = delete;
    SubscriptionTokenImplBase& operator=(const SubscriptionTokenImplBase&&) = delete;
 
    virtual ~SubscriptionTokenImplBase();
 
    virtual void SetMaxQueueLength(size_t length) = 0;
 
    virtual void Unsubscribe() = 0;
};
 
}  // namespace impl
 
/// @brief RAII subscription guard, that is usually retrieved from
/// storages::redis::SubscribeClient.
///
/// See storages::redis::MockSubscriptionTokenImpl for hints on mocking and
/// testing.
class [[nodiscard]] SubscriptionToken final {
public:
    using OnMessageCb = std::function<void(const std::string& channel, const std::string& message)>;
    using OnPmessageCb = std::function<
        void(const std::string& pattern, const std::string& channel, const std::string& message)>;
 
    SubscriptionToken();
    SubscriptionToken(SubscriptionToken&&) noexcept;
 
    /// This constructor can be used in tests/mocks to create your own
    /// subscription token
    SubscriptionToken(std::unique_ptr<impl::SubscriptionTokenImplBase>&& implementation);
 
    ~SubscriptionToken();
 
    SubscriptionToken& operator=(SubscriptionToken&&) noexcept;
 
    /// There is a MPSC queue inside the connection. This parameter regulates
    /// its maximum length. If it overflows, new messages are discarded.
    void SetMaxQueueLength(size_t length);
 
    /// Unsubscribe from the channel. This method is synchronous, once it
    /// returned, no new calls to callback will be made.
    void Unsubscribe();
 
    /// Checks that token is not empty. Empty token has no implementation
    /// inside. This method is mostly useful in unit tests. All methods
    /// of this class work correctly on empty tokens.
    bool IsEmpty() const noexcept { return impl_ == nullptr; }
 
private:
    std::unique_ptr<impl::SubscriptionTokenImplBase> impl_;
};
 
}  // namespace storages::redis
 
USERVER_NAMESPACE_END