# @graphile/pg-pubsub

This PostGraphile [server
plugin](https://www.graphile.org/postgraphile/plugins/) provides a `pubsub`
instance to [schema
plugins](https://www.graphile.org/postgraphile/extending/) that uses
PostgreSQL `LISTEN`/`NOTIFY` to provide realtime features.

Also adds support for `@pgSubscriptions` directive to easily define your own
subscriptions using LISTEN/NOTIFY with `makeExtendSchemaPlugin`; and adds the
`--simple-subscriptions` feature which, when enabled, adds a simple `listen`
subscription field to your GraphQL API.

It's intended that you use this plugin as a provider of realtime data to
other plugins which can use it to add subscription fields to your API.

For full documentation, see: https://www.graphile.org/postgraphile/subscriptions/

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## Usage

CLI:

```
yarn add @graphile/pg-pubsub

postgraphile \
  --plugins @graphile/pg-pubsub \
  --subscriptions \
  --simple-subscriptions \
  -c postgres:///mydb
```

Library:

```js
const express = require("express");
const { postgraphile, makePluginHook } = require("postgraphile");
const { default: PgPubsub } = require("@graphile/pg-pubsub");

const pluginHook = makePluginHook([PgPubsub]);

const postgraphileOptions = {
  pluginHook,
  subscriptions: true, // Enable PostGraphile websocket capabilities
  simpleSubscriptions: true, // Add the `listen` subscription field
  subscriptionEventEmitterMaxListeners: 20, // Set max listeners on eventEmitter, 0 unlimited, 10 default
  websocketMiddlewares: [
    // Add whatever middlewares you need here, note that they should only
    // manipulate properties on req/res, they must not sent response data. e.g.:
    //
    //   require('express-session')(),
    //   require('passport').initialize(),
    //   require('passport').session(),
  ],
};

const app = express();
app.use(postgraphile(databaseUrl, "app_public", postgraphileOptions));
app.listen(parseInt(process.env.PORT, 10) || 3000);
```