A practical Example as a form of Documentation

shantanoo-desai commented 5 years ago

Hi @davidyaha I am working on this repository with express-graphql and was looking into documenting a practical example via MQTT. I am not using typescript but standard ES6 stuff. Would you be able to just guide me with how do I get the data from the Broker out?

Progress

Defined a Schema as following:

schema.js

        type Result {
            payload: String
        }

        input TopicInput {
            topic: String!
        }

        type RootSubscription {
            subscribeSite(topicInput: TopicInput): Result
        }

       schema {
            query: RootQuery
            mutation: RootMutation
            subscription: RootSubscription
        }

resolvers.js

I did the following:

const { MQTTPubSub } = require('graphql-mqtt-subscriptions');
const { connect } = require('mqtt');

const client = connect('my.mqtt.broker.address', {
    reconnectPeriod: 1000
});

const pubsub = new MQTTPubSub({
    client
});

within the resolver function:

subscribeSite: (args) => {
    pubsub.asyncIterator(args.topicInput.topic)
}

I am not sure how do I get the value from the asynIterator at this point and return it to the GraphiQL UI.

I already have a setup where live data is sent via sensor nodes and maybe the repo could benefit from a nice working example writeup

shantanoo-desai commented 5 years ago

will reopen it once a concrete setup is up and running

shantanoo-desai commented 5 years ago

Based on #11 I will write a blog post to practically use this repo alongside graphql

davidyaha commented 5 years ago

Sounds great @shantanoo-desai! Please link it here when it's up!

btw, all subscription packages work similarly so you might want to head over to apollo's graphql-subscriptions repo to get information about asyncIterables and the api to transform and filter them. This package is intended to be more like an addon to graphql-subscriptions because the actual pubsub manager can be easily replaced for something like redis / rabbitmq or whatever actually.

Regarding your issue here:

subscribeSite: (args) => {
    pubsub.asyncIterator(args.topicInput.topic)
}

Please note that you are not returning anything in this arrow function. The simplest form of subscription resolver should return an object with a subscribe property that has an iterable factory.

There are good examples here: https://github.com/apollographql/graphql-subscriptions#getting-started-with-your-first-subscription

Let me know if you need anymore help there and I would love to merge a working example to this repo's README file.

shantanoo-desai commented 5 years ago

Hi @davidyaha I have written a blog post documenting a live IoT Data along side MQTT GraphQL Endpoint with Apollo Server here. Let me know if you find this useful or not.

davidyaha commented 5 years ago

@shantanoo-desai 🎉 🎉 Awesome use case!! Would love to see an app that utilizes this graphql api!

shantanoo-desai commented 5 years ago

@davidyaha I do actually have something in mind but requires a bit more thought. I figured out that GraphQL Schemas can Adapt EPCIS aka. product RFID very well.

An really practical example might be Subscribing to live product tracking within companies or factories via MQTTPubSub.

davidyaha / graphql-mqtt-subscriptions

A practical Example as a form of Documentation #10

Progress