notify.hpp

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#pragma once
 
/// @file userver/storages/postgres/notify.hpp
/// @brief Asynchronous notifications
 
#include <userver/storages/postgres/options.hpp>
#include <userver/utils/fast_pimpl.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::postgres {
 
namespace detail {
class ConnectionPtr;
}
 
struct Notification {
    std::string channel;
    std::optional<std::string> payload;
};
 
/// @brief RAII scope for receiving notifications.
///
/// Used for waiting for notifications on PostgreSQL connections. Created by
/// calling storages::postgres::Cluster::Listen(). Exclusively holds a
/// connection from a pool.
///
/// Non-copyable.
///
/// @par Usage synopsis
/// @code
/// auto scope = cluster.Listen("channel");
/// cluster.Execute(pg::ClusterHostType::kMaster,
///                 "select pg_notify('channel', NULL)");
/// auto ntf = scope.WaitNotify(engine::Deadline::FromDuration(100ms));
/// @endcode
class [[nodiscard]] NotifyScope final {
public:
    NotifyScope(detail::ConnectionPtr conn, std::string_view channel, OptionalCommandControl cmd_ctl);
 
    ~NotifyScope();
 
    NotifyScope(NotifyScope&&) noexcept;
    NotifyScope& operator=(NotifyScope&&) noexcept;
 
    NotifyScope(const NotifyScope&) = delete;
    NotifyScope& operator=(const NotifyScope&) = delete;
 
    /// Wait for notification on connection
    Notification WaitNotify(engine::Deadline deadline);
 
private:
    struct Impl;
    USERVER_NAMESPACE::utils::FastPimpl<Impl, 80, 8> pimpl_;
};
 
}  // namespace storages::postgres
 
USERVER_NAMESPACE_END