https://github.com/siamahnaf/graphql-pg-subscriptions
This package implements the PubSubEngine Interface from the graphql-subscriptions package and also the new AsyncIterator interface. It allows you to connect your subscriptions manger to a postgres based Pub Sub mechanism to support multiple subscription manager instances.
https://github.com/siamahnaf/graphql-pg-subscriptions
graphql graphql-subscriptions pg-subscription-billing postgresql subscription
Last synced: 2 months ago
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This package implements the PubSubEngine Interface from the graphql-subscriptions package and also the new AsyncIterator interface. It allows you to connect your subscriptions manger to a postgres based Pub Sub mechanism to support multiple subscription manager instances.
- Host: GitHub
- URL: https://github.com/siamahnaf/graphql-pg-subscriptions
- Owner: siamahnaf
- License: mit
- Created: 2024-06-15T17:20:56.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-11-21T07:04:10.000Z (11 months ago)
- Last Synced: 2025-07-18T11:13:51.829Z (3 months ago)
- Topics: graphql, graphql-subscriptions, pg-subscription-billing, postgresql, subscription
- Language: TypeScript
- Homepage: https://www.npmjs.com/package/graphql-pg-subscriptions
- Size: 13.7 KB
- Stars: 3
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Graphql PG Subscription
A graphql subscriptions implementation using postgres and apollo's graphql-subscriptions.
This package implements the PubSubEngine Interface from the graphql-subscriptions package and also the new AsyncIterator interface. It allows you to connect your subscriptions manger to a postgres based Pub Sub mechanism to support multiple subscription manager instances.
# Features
- Properly Maintained
- Small In Size
- Larger Payload Problem Solved (I use pg table for the payload. So now larger payload can pass) - (PG Default Notify has size limit, that's why you can't provide larger payload.);
- Fully TypeScript Support
- Worked with any framework (ExpressJS, NestJS)
## Installation
```bash
npm i graphql-pg-subscriptions
```
## Usage
First of all, follow the instructions in [graphql-subscriptions](https://github.com/apollographql/graphql-subscriptions) to add subscriptions to your app.
Afterwards replace `PubSub` with `PostgresPubSub`:
```js
// Before
import { PubSub } from "graphql-subscriptions";
export const pubsub = new PubSub();
```
```js
//After
import { PostgresPubSub } from "graphql-postgres-subscriptions";
import { Client } from "pg";
const client = new Client({
user: 'dbuser',
host: 'database.server.com',
database: 'mydb',
password: 'secretpassword',
port: 3211,
});
client.connect();
const pubsub = new PostgresPubSub({ client, maxListeners: 15 });
//You can increase max event listeners if you need, default is 15
```
### commonMessageHandler
The second argument to `new PostgresPubSub()` is the `commonMessageHandler`. The common message handler gets called with the received message from PostgreSQL.
You can transform the message before it is passed to the individual filter/resolver methods of the subscribers.
This way it is for example possible to inject one instance of a [DataLoader](https://github.com/facebook/dataloader) which can be used in all filter/resolver methods.
```javascript
const getDataLoader = () => new DataLoader(...)
const commonMessageHandler = ({attributes: {id}, data}) => ({id, dataLoader: getDataLoader()})
const pubsub = new PostgresPubSub({ client, commonMessageHandler });
```
```javascript
export const resolvers = {
Subscription: {
somethingChanged: {
resolve: ({ id, dataLoader }) => dataLoader.load(id)
}
}
};
```
## Error handling
`PostgresPubSub` instances emit a special event called `"error"`. This event's payload is an instance of Javascript's `Error`. You can get the error's text using `error.message`.
```js
const ps = new PostgresPubSub({ client });
ps.subscribe("error", err => {
console.log(err.message); // -> "payload string too long"
}).then(() => ps.publish("a", "a".repeat(9000)));
```
For example you can log all error messages (including stack traces and friends) using something like this:
```js
ps.subscribe("error", console.error);
```
## Stay in touch
- Author - [Siam Ahnaf](https://www.siamahnaf.com/)
- Website - [https://www.siamahnaf.com/](https://www.siamahnaf.com/)
- Twitter - [https://twitter.com/siamahnaf198](https://twitter.com/siamahnaf198)
- Github - [https://github.com/siamahnaf](https://github.com/siamahnaf)