postgres_listener_service Class Reference

Manages a dedicated PostgreSQL connection to listen for NOTIFY events. More...

#include <postgres_listener_service.hpp>

Collaboration diagram for postgres_listener_service:

Public Types
using	notification_callback_t = std::function< void(const domain::entity_change_event &)>
	Type alias for the notification callback function.

Public Member Functions
	postgres_listener_service (database::context ctx, notification_callback_t callback)
	Constructs a postgres_listener_service.
	~postgres_listener_service ()
	Destroys the postgres_listener_service.
	postgres_listener_service (const postgres_listener_service &)=delete
postgres_listener_service &	operator= (const postgres_listener_service &)=delete
void	start ()
	Starts the listener thread and begins listening for notifications.
void	stop ()
	Stops the listener thread and waits for it to join.
void	subscribe (const std::string &channel_name)
	Subscribes to a PostgreSQL NOTIFY channel.
void	notify (const std::string &channel_name, const std::string &payload)
	Sends a NOTIFY on a PostgreSQL channel.

Detailed Description

Manages a dedicated PostgreSQL connection to listen for NOTIFY events.

This service runs a separate thread to continuously listen for asynchronous notifications on configured channels. When a notification is received, it parses the payload into a domain::entity_change_event object and dispatches it via a callback.

The service maintains its own dedicated connection separate from any connection pool, as LISTEN/NOTIFY requires a persistent connection.

Member Typedef Documentation

notification_callback_t

using notification_callback_t = std::function<void(const domain::entity_change_event&)>

Type alias for the notification callback function.

The callback is invoked with the parsed domain::entity_change_event object. Note: The callback is invoked from the listener thread, so implementations should be thread-safe and non-blocking.

Constructor & Destructor Documentation

postgres_listener_service()

postgres_listener_service ( database::context  ctx, notification_callback_t  callback  )

explicit

Constructs a postgres_listener_service.

Creates a dedicated PostgreSQL connection for listening using the credentials from the provided database context.

Parameters

ctx	The database context containing connection credentials.
callback	The callback function to be invoked when a notification is received.

~postgres_listener_service()

~postgres_listener_service

(

)

Destroys the postgres_listener_service.

Stops the listener thread and closes the dedicated connection.

Member Function Documentation

start()

void start

(

)

Starts the listener thread and begins listening for notifications.

Any channels subscribed via subscribe() before calling start() will have LISTEN commands issued when the thread starts.

Here is the caller graph for this function:

subscribe()

void subscribe

(

const std::string &

channel_name

)

Subscribes to a PostgreSQL NOTIFY channel.

Can be called before or after start(). If called before start(), the LISTEN command will be issued when the listener thread starts. If called after start(), the LISTEN command is issued immediately on the dedicated connection.

Parameters

channel_name

The name of the channel to listen on (e.g., "ores_currencies").

Here is the caller graph for this function:

notify()

void notify	(	const std::string &	channel_name,
		const std::string &	payload
	)

Sends a NOTIFY on a PostgreSQL channel.

Parameters

channel_name	The name of the channel to notify.
payload	The payload string to send with the notification.