pg_listen

Simple listener to PostgreSQL notifications.

Dependencies

To run this program, you will need Node.js and yarn/npm installed. I tested it on Node.js v16.14.0 and yarn v1.22.18.

Instalation

Clone this repository:

git clone https://github.com/Ghasteek/pg_listen.git

Go to its folder:

cd pg_listen

Install all packages:

yarn install

Configuration

By default, app will take file config.conf from same folder as it resides. However, you can change path and filename of config file by adding -c path/to/config.cfg.
Default config file uses yaml syntax, and its structure should be like this:

pgasync_url: postgres://pg_user:pg_password@pg_server:_pg_port/pg_database

listen:
  - notification_1
  - notification_2
  ...

• pgasync_url - classic postgresql connection string
• listen - array of notifications you want to listen to

Parameters

• -c path/to/config.cfg - optional, path to configuration file, default config.cfg
• -n notification1,notification2 - optional, comma separated list of notifications to listen, default list is in config file, which will be ignored, if list is passed by this parameter

Run

After editing config file, start program by running

node pg_listen

After launch, you will see info about connecting and listening to notifications:

Connected to database "pg_database" at pg_server:pg_port.

Listening to notifications "notification_1".
Listening to notifications "notification_2".

PostgreSQL notification can send only text, but this application will try to convert notification to JSON and then print it.

Incoming notification "notification_1" -
{
  "key1": "value",
  "key2": "value",
  "key3": [
        "value1",
        "value2"
      ],
}

If only text is passed down by notification, it will print just that:

Incoming notification "notification_1" -
Text of your notification

End

Hope you will enjoy this simple piece of code, that helped me at my work :)