subscription-blog

A simple example of subscriptions in StepZen. Any query in StepZen can be converted into a subscription. To give an example:

type Query {
    foo: Foo
    @rest (endpoint: "...")
}
type Subscription {
    fooSub: Foo @materializer (query:"foo")
}

That's it! foo can be a @rest query, it could be @dbquery, it could be a federated @graphql query, it could be an @sequence. Any way you construct your queries, each and everyone of them can be converted into a subscription! (Underneath the covers, StepZen does long polling to determine what has changed, and more mechanisms are coming, but you can start using it right now, and we will continue to optimize it.)

Steps for local service

1. Download this repo and cd subscription-blog/graphql.
2. If you do not have stepzen installed, then npm install -g stepzen.
3. cd graphql && stepzen service start && stepzen login --config ~/.stepzen/stepzen-config.local.yaml--this starts a local docker container running all of StepZen's services.
4. stepzen deploy deploys the graphql schema in index.graphql to StepZen (on your local machine) and the endpoint is http://localhost:9000/api/subscription/__graphql. However, the URL for web sockets is ws://localhost:9000/stepzen-subscriptions/api/subscription/__graphql.
5. Now we will have a client that makes subscription requests over WebSockets using graphql-ws to this endpoint. For this, cd ../client && npm install.
6. Setup .env; echo 'APIKEY='$(stepzen whoami --apikey) > .env (stepzen whoami --apikey retrieves your admin key, it shoud look something like: graphql::local.net...)
7. node client.js and see the magic. You will see the price of ETHBTC change and reflected back on your console.

Steps for the StepZen cloud service

1. Download this repo and cd subscription-blog/graphql.
2. Make sure you've registered for an account and setup your cli. Getting Started has instructions on how to do this.
3. cd graphql && stepzen deploy deploys the graphql schema in index.graphql to the StepZen managed service and the websockets endpoint is wss://ACCOUNT.stepzen.net/stepzen-subscriptions/api/subscription/__graphql. Note: the client code below will use the correct wss endpoint if you set STEPZEN_ACCOUNT per step 6.
4. Now we will have a client that makes subscription requests over WebSockets using graphql-ws to this endpoint. For this, cd ../client && npm install.
5. Do a stepzen whoami --apikey to get your admin key. Edit .env and set:
   • the value of APIKEY= to be this key
   • the value of STEPZEN_ACCOUNT= to be your stepzen account name
6. node client.js and see the magic. You will see the price of ETHBTC change and reflected back on your console.

How this all works

The subscription is against a REST backend: https://api.binance.us/api/v3/ticker?symbol=ETHBTC and StepZen does a long polling and pushes back to the client whenever a new value is found.

Because any Query field can be exposed as a Subscription, you can set up subscription against databases, graphql endpoints, or any combination thereof. Try them for yourself.