Local Subgraph Development

While you're working on changes to one of your subgraphs, you can run a version of your entire supergraph locally in your development environment. To do this, you use the rover dev command.

The rover dev command monitors each of your subgraph schemas (either via server introspection or by watching a .graphql file). Whenever it detects a change, it automatically recomposes your router's supergraph schema and raises any errors that might occur. This enables you iterate quickly on schema changes.

Starting your router

You run rover dev once for each subgraph in your supergraph. The first time you run it, Rover spins up a router on your local machine.

Try running rover dev with an example subgraph like so:

rover dev --url https://flyby-locations-sub.herokuapp.com/ --name locations

You'll see output like the following:

1
WARN: could not detect a schema in the current working directory. to watch a schema, pass the `--schema <PATH>` argument
2
👂 polling https://flyby-locations-sub.herokuapp.com/ every 1 second
3
⚠️  Do not run this command in production! ⚠️  It is intended for local development.
4
🛫 starting a session with the 'locations' subgraph
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🎶 composing supergraph with Federation v2.1.2
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🚀 your supergraph is running! head to http://localhost:3000 to query your supergraph

You can now open http://localhost:3000 in your browser and run test queries against your local router using the Explorer!

You can replace the example subgraph URL and name in the above command with the details for your own subgraph. You can provide a remote URL or a localhost URL.

Adding a subgraph

To add a subgraph to your local supergraph, run rover dev again in a separate terminal window.

You can add a subgraph to this article's example supergraph with the following command:

rover dev --url https://flyby-reviews-sub.herokuapp.com/ --name reviews

This command's output is similar to the output for the initial execution, but it includes a line like the following:

1
🐤 adding the 'reviews' subgraph to the session

This indicates that rover dev has identified your existing supergraph session and is adding this subgraph to it.

Now if you run test queries in the Explorer, you'll see that they can include fields from both the locations and reviews subgraphs!

Ending a rover dev session

To shut down your local supergraph, use CTRL+C to stop the first rover dev process you started. This automatically terminates all secondary rover dev processes that are part of the same session.

Command options

For more details on rover dev options, see the Rover documentation.