Subscribing

Technology

So this is a bit tricky. If every graphql request is plain HTTP request with query/variables data. Subscription needs a websocket connection and a special handshake. Also every request is a bit different. So thanks to apollographql/subscriptions-transport-ws and websockets/ws we can implement subscriptions from the box If you need regular queries via WS transport, please open an issue.

Connection

So ws link is grabbed from graphqlUrl setting, but you can set it manually by wsUrl. A connection is lazy, so it will be establised only when you will first time subscribe

const { Hasura } = require('hasura-om')

const orm = new Hasura({
    graphqlUrl: 'hasura graphql endpoint',
    wsUrl: 'hasura ws endpoint',
    adminSecret: 'your hasura admin secret',
    wsConnectionSettings: {
        lazy: false //here you can set a connection just with Hasura object
    }
}) 
await orm.generateTablesFromAPI()

Subscribing

Subscription is a regular query (select or aggregate, only one at a time) but you will get a response every time some fields in your request will change

function usersOnline([err, data]) {
    //todo with data.count
}

let unsub = orm.subscribe({
    user: {
        aggregate: {
            where: { isOnline: { _eq: true } },
            count: {}
        }
    },
}, usersOnline)

unsub is a function to unsubscribe to updates. Just call unsub()

Debuging connection

orm.$ws is an EventEmitter and will emit every event from a ws client

let tsStart = new Date().getTime()
let timediff = function () {
    return `+${ ((new Date().getTime() - tsStart)/1000).toFixed(2) }s`
}

orm.$ws.on('connected', () => {
    console.log(timediff(), 'orm.$ws.on.connected')
})
orm.$ws.on('connecting', () => {
    console.log(timediff(), 'orm.$ws.on.connecting')
})
orm.$ws.on('reconnected', () => {
    console.log(timediff(), 'orm.$ws.on.reconnected')
})
orm.$ws.on('reconnecting', () => {
    console.log(timediff(), 'orm.$ws.on.reconnecting')
})
orm.$ws.on('disconnected', () => {
    console.log(timediff(), 'orm.$ws.on.disconnected')
})
orm.$ws.on('error', (data) => {
    console.log(timediff(), 'orm.$ws.on.error', data)
})