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https://github.com/voxpelli/node-pg-pubsub
A Publish/Subscribe implementation on top of PostgreSQL NOTIFY/LISTEN
https://github.com/voxpelli/node-pg-pubsub
node-js postgres pubsub
Last synced: about 1 month ago
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A Publish/Subscribe implementation on top of PostgreSQL NOTIFY/LISTEN
- Host: GitHub
- URL: https://github.com/voxpelli/node-pg-pubsub
- Owner: voxpelli
- License: mit
- Created: 2014-12-06T22:43:14.000Z (over 9 years ago)
- Default Branch: main
- Last Pushed: 2024-05-28T01:25:44.000Z (about 1 month ago)
- Last Synced: 2024-05-29T12:43:23.804Z (about 1 month ago)
- Topics: node-js, postgres, pubsub
- Language: JavaScript
- Homepage: https://www.npmjs.com/package/pg-pubsub
- Size: 131 KB
- Stars: 233
- Watchers: 7
- Forks: 16
- Open Issues: 18
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Lists
- awesome-stars - voxpelli/node-pg-pubsub - A Publish/Subscribe implementation on top of PostgreSQL NOTIFY/LISTEN (JavaScript)
README
# PG PubSub
A Publish/Subscribe implementation on top of [PostgreSQL NOTIFY/LISTEN](https://www.postgresql.org/docs/current/sql-notify.html)
[](https://www.npmjs.com/package/pg-pubsub)
[](https://www.npmjs.com/package/pg-pubsub)
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## Installation
```bash
npm install pg-pubsub --save
```
## Requirements
* Postgres >= 9.4
## Usage
```js
const PGPubsub = require('pg-pubsub');
const pubsubInstance = new PGPubsub(uri[, options]);
```
### Options
```js
{
[log]: Function // default: silent when NODE_ENV=production, otherwise defaults to console.log(...)
}
```
### Methods
* **addChannel(channelName[, eventListener])** – starts listening on a channel and optionally adds an event listener for that event. As `PGPubsub` inherits from `EventEmitter` one can also add it oneself. Returns a `Promise` that resolves when the listening has started.
* **removeChannel(channelName[, eventListener])** – either removes all event listeners and stops listeneing on the channel or removes the specified event listener and stops listening on the channel if that was the last listener attached.
* **publish(channelName, data)** – publishes the specified data JSON-encoded to the specified channel. It may be better to do this by sending the `NOTIFY channelName, '{"hello":"world"}'` query yourself using your ordinary Postgres pool, rather than relying on the single connection of this module. Returns a `Promise` that will become rejected or resolved depending on the success of the Postgres call.
* **close(): Promise** – closes down the database connection and removes all listeners. Useful for graceful shutdowns.
* All [EventEmitter methods](http://nodejs.org/api/events.html#events_class_events_eventemitter) are inherited from `EventEmitter`
### Examples
#### Simple
```javascript
const pubsubInstance = new PGPubsub('postgres://username@localhost/database');
await pubsubInstance.addChannel('channelName', function (channelPayload) {
// Process the payload – if it was JSON that JSON has been parsed into an object for you
});
await pubsubInstance.publish('channelName', { hello: "world" });
```
The above sends `NOTIFY channelName, '{"hello":"world"}'` to PostgreSQL, which will trigger the above listener with the parsed JSON in `channelPayload`.
#### Advanced
```javascript
const pubsubInstance = new PGPubsub('postgres://username@localhost/database');
await pubsubInstance.addChannel('channelName');
// pubsubInstance is a full EventEmitter object that sends events on channel names
pubsubInstance.once('channelName', channelPayload => {
// Process the payload
});
```
## Description
Creating a `PGPubsub` instance will not do much up front. It will prepare itself to start a Postgres connection once the first channel is added and then it will keep a connection open until its shut down, reconnecting it if it gets lost, so that it can constantly listen for new notifications.
## Lint / Test
- setup a postgres database to run the integration tests
- the easist way to do this is via docker, `docker run -it -p 5432:5432 -e POSTGRES_DB=pgpubsub_test postgres`
- `npm test`
For an all-in-one command, try:
```sh
# fire up a new DB container, run tests against it, and clean it up!
docker rm -f pgpubsub_test || true && \
docker run -itd -p 5432:5432 -e POSTGRES_DB=pgpubsub_test --name pgpubsub_test postgres && \
npm test && \
docker rm -f pgpubsub_test
```