https://github.com/frafra/postgresql2websocket

Send PostgreSQL notifications over websockets
https://github.com/frafra/postgresql2websocket

aiohttp asyncpg notifications postgresql python python3 python35 python36 python37 trigger websockets

Last synced: 3 months ago
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Send PostgreSQL notifications over websockets

• Host: GitHub
• URL: https://github.com/frafra/postgresql2websocket
• Owner: frafra
• License: gpl-3.0
• Created: 2017-01-23T09:58:29.000Z (about 8 years ago)
• Default Branch: master
• Last Pushed: 2023-03-13T04:59:31.000Z (almost 2 years ago)
• Last Synced: 2024-10-13T19:07:49.896Z (3 months ago)
• Topics: aiohttp, asyncpg, notifications, postgresql, python, python3, python35, python36, python37, trigger, websockets
• Language: Python
• Size: 73.2 KB
• Stars: 82
• Watchers: 5
• Forks: 10
• Open Issues: 5
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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• jimsghstars - frafra/postgresql2websocket - Send PostgreSQL notifications over websockets (Python)

README

        
# postgresql2websocket

[![CircleCI](https://img.shields.io/circleci/build/github/frafra/postgresql2websocket.svg)](https://circleci.com/gh/frafra/workflows/postgresql2websocket)

## How does it work?

Execute `postgresql2websocket.py` and connect to `ws://localhost:8080/channel` where `channel` is the channel name of the selected database (see [PostgreSQL documentation - NOTIFY](https://www.postgresql.org/docs/current/static/sql-notify.html)).

## How to configure it?

Copy `postgresql2websocket.conf.example` as `postgresql2websocket.conf` and change the values according to your needs.

## What technologies are you using?

* [PostgreSQL](https://www.postgresql.org/)

* [Python](https://www.python.org/) (3.5.3 or greater)

* [aiohttp](http://aiohttp.readthedocs.io/) + [asyncpg](https://github.com/MagicStack/asyncpg)

* [Poetry](https://poetry.eustace.io/) for dependency management

## What can I do with it?

You can create a trigger on a table in order to get notifications over a websocket in real time. For example, this function send a notification using the `postgresql2websocket` channel containing the action that has been performed and a JSON representation of the row.

```

CREATE OR REPLACE FUNCTION table_update_notify() RETURNS trigger AS $$

DECLARE

  rec RECORD;

BEGIN

  IF TG_OP = 'INSERT' OR TG_OP = 'UPDATE' THEN

    rec = NEW;

  ELSE

    rec = OLD;

  END IF;

  -- postgresql2websocket is the default channel name

  PERFORM pg_notify('postgresql2websocket', json_build_object('table', TG_TABLE_NAME, 'type', TG_OP, 'row', row_to_json(rec))::text);

  RETURN NEW;

END;

$$ LANGUAGE plpgsql;

```

Then you can trigger this function when something happens on `mytable`:

```

CREATE TRIGGER mytable_notify_update AFTER UPDATE ON mytable FOR EACH ROW EXECUTE PROCEDURE table_update_notify();

CREATE TRIGGER mytable_notify_insert AFTER INSERT ON mytable FOR EACH ROW EXECUTE PROCEDURE table_update_notify();

CREATE TRIGGER mytable_notify_delete AFTER DELETE ON mytable FOR EACH ROW EXECUTE PROCEDURE table_update_notify();

```

## Bidirectional communication

The websocket channel can be used to execute remote functions too:

For example:

```

CREATE FUNCTION add(integer, integer) RETURNS integer

    AS 'select $1 + $2;'

    LANGUAGE SQL

    IMMUTABLE

    RETURNS NULL ON NULL INPUT;

```

Executing `ws.send('select add(1, 2);')` will return a JSON response containing `{"add": 3}`.

## How to use it?

Execute `postgresql2websocket.py`, open `examples/console.html` and execute some operations on the table.

## Limitations

> The "payload" string to be communicated along with the notification. This must be specified as a simple string literal. In the default configuration it must be shorter than 8000 bytes. (If binary data or large amounts of information need to be communicated, it's best to put it in a database table and send the key of the record.)

Source: https://www.postgresql.org/docs/current/static/sql-notify.html