pgbroadcaster

Usage

Postgres

CREATE OR REPLACE FUNCTION notify_event() RETURNS TRIGGER AS $$
 DECLARE 
 data json;
 notification json;
 
 BEGIN
 
 -- Convert the old or new row to JSON, based on the kind of action.
 -- Action = DELETE? -> OLD row
 -- Action = INSERT or UPDATE? -> NEW row
 IF (TG_OP = 'DELETE') THEN
 data = row_to_json(OLD);
 ELSE
 data = row_to_json(NEW);
 END IF;
 
 -- Contruct the notification as a JSON string.
 notification = json_build_object(
 'table',TG_TABLE_NAME,
 'action', TG_OP,
 'data', data);
 
 
 -- Execute pg_notify(channel, notification)
 PERFORM pg_notify('events',notification::text);
 
 -- Result is ignored since this is an AFTER trigger
 RETURN NULL; 
 END;
 
$$ LANGUAGE plpgsql;

CREATE TRIGGER exampletable_notify_event
AFTER INSERT OR UPDATE OR DELETE ON exampletable
 FOR EACH ROW EXECUTE PROCEDURE notify_event();

Server

package main
import (
	"log"
	"net/http"
	"fmt"
	"github.com/coussej/pgbroadcast"
)
func main() {
	// Create a new broadcaster
	pb, err := pgbroadcaster.NewPgBroadcaster("dbname=exampledb user=webapp password=webapp")
	// listen to the events channel
	err = pb.Listen("events")
	if err != nil {
		fmt.Println(err)
	}
	// server the websocket	
	http.HandleFunc("/ws", pb.ServeWs)
	err = http.ListenAndServe(":6060", nil)
	if err != nil {
		log.Fatal("ListenAndServe: ", err)
	}
}

Client

 $(function() {
 var conn;
 if (window["WebSocket"]) {
 conn = new WebSocket("ws://localhost/ws");
 conn.onopen = function(evt) {
 // SUBSCRIBE TO TABLE
 conn.send("exampletable");
 } 
 conn.onclose = function(evt) {
 // HANDLE CONNECTION CLOSE
 } 
 conn.onmessage = function(evt) {
 var data = JSON.parse(evt.data);
 // HANDLE DATA
 }
 } 
 });