Overview

To set up subscriptions via HTTP callback in our graph, we need to modify our router-config.yaml file that sets our router's settings. Let's jump in there now.

This starts with a top-level property called subscription, and right away we set an enabled property to true.

Next, we specify the mode. Our mode is callback, which we'll place on a new line so we can specify additional properties.

Now under callback we need to set a number of properties.

• public_url
• listen
• path
• heartbeat_interval
• subgraphs

Let's start with those first three properties, because they're related:

• The public_url property represents the router's public URL that subgraphs must be able to send new subscription data to. By default, a locally running router runs on http://127.0.0.1:4000, and we've appended /callback as the specific endpoint the subgraphs should use when "calling back" to the router.

• The listen property specifies the IP address and port the router will listen on for subscription callbacks. We haven't changed it from the default value here; but note that for security reasons, it's best to expose a separate port that's available only through your internal network.

• The path property states the specific path of our router's callback endpoint. It should match the value appended to the public_url. If you don't specify a path here, it takes the value of /callback by default.

Finally, we can add the last two properties. heartbeat_interval specifies the interval at which the subgraph should "check in" with the router to make sure communication is still possible. This property is optional, but we'll include it as 5s. Lastly we specify which subgraphs implement this protocol.

With these settings in place, let's restart our router so it can pick them up. (Swap in your graph's unique APOLLO_GRAPH_REF and APOLLO_KEY.)