The Rover dev Command

A supergraph is an architecture consisting of multiple GraphQL APIs (subgraphs) and a graph router that runs in front of them:

While you're making local changes to an individual subgraph, you can use the rover dev command to start a local router instance and test the effects of subgraph changes on your entire supergraph.

Whenever you add, modify, or remove a subgraph from your local supergraph, Rover automatically re-composes your individual subgraph schemas into a unified supergraph schema and provides it to your local router session.

Starting a router session

To use rover dev, you need at least one running GraphQL API (subgraph). Rover can obtain a subgraph's schema via introspection (either standard or federated introspection), or you can provide a local schema file.

Here's an example rover dev command that points to a locally running subgraph and provides its schema via a local file:

rover dev --name products --schema ./products.graphql --url http://localhost:4000

When you start your first rover dev process:

1. Rover obtains the subgraph schema(s) you provide via the supergraph config file.

2. Rover composes a supergraph schema from the subgraph schema(s).

3. Rover starts a locally running router session and provides it the supergraph schema.

4. Rover starts watching the provided subgraph schema(s) for changes, recomposing the supergraph schema whenever it detects a change. This automatically reloads the router.

5. When provided via the --router-config CLI option, Rover starts watching the router config for changes, automatically reloading the router whenever it detects a change.

Starting a session with multiple subgraphs

If you work with a standard set of subgraphs, you can create a supergraph config file and add all of them to your local router session with a single rover dev command.

For example, this supergraph.yaml file provides the necessary details for two subgraphs:

federation_version: =2.4.7
subgraphs:
  products:
    routing_url: http://localhost:4000
    schema:
      file: ./products.graphql # Schema provided via file
  reviews:
    schema:
      subgraph_url: http://localhost:4001 # Schema provided via introspection, routing_url can be omitted
  users:
    # routing_url: <Optional, pulled from GraphOS registry by default>
    schema:  # Schema downloaded from GraphOS registry, does not poll for updates
      graphref: mygraph@current
      subgraph: actors

You provide this file to rover dev like so:

rover dev --supergraph-config supergraph.yaml

If you do, a router session starts with one of the subgraphs listed, then adds the remaining subgraphs one at a time (order is undefined). Because of this, you might observe composition errors during intermediate steps.

Providing a supergraph.yaml file also enables you to take advantage of other config options, such as introspection_headers.

Rover watches the supergraph config file for changes, allowing you to add, remove, or update subgraphs, making those changes available to the router instance. Only one config file may be used at a time for the rover dev session.

Starting a session from a GraphOS Studio variant

To start a local router instance using a GraphOS Studio variant, include the variant's graph ref with the --graph-ref option like so:

rover dev --graph-ref docs-example-graph@current

When you include a graph ref, Rover uses the associated variant's subgraph routing URLs and schemas from Studio as the supergraph config. You can view a variant's subgraphs, including their routing URLs and schemas, on the variant's Subgraphs page in Studio. You may also use remote subgraphs in your supergraph config file. See the actors subgraph in the supergraph.yaml example above for the syntax.

Overriding variant subgraphs

While developing locally, you may want to override one or more subgraph(s) in your Studio variant with subgraphs from your local environment. You can do this by passing a supergraph config file alongside a graph ref. Any subgraphs defined in the supergraph config file override those from the graph ref.

For example, given a supergraph_override.yaml file like this:

subgraphs:
  products:
    routing_url: http://localhost:4000
    schema:
      file: ./products.graphql

You can override a variant's published products subgraph like so:

rover dev \
  --graph-ref docs-example-graph@current \
  --supergraph-config path/to/supergraph_override.yaml

This command overrides the variant's published products subgraph in your local development session. If the Studio variant doesn't include a products subgraph, this command adds the subgraph and recomposes the supergraph schema.

Overriding federation versions

You can also use a supergraph config file to safely test a new federation version locally before putting it in production.

For example, given a federation_override.yaml file like this:

federation_version: =2.4.7

You can override a variant's federation version like so:

rover dev \
  --graph-ref docs-example-graph@current \
  --supergraph-config federation_override.yaml

You can also override a variant's federation version by passing the --federation-version option. This argument accepts fully qualified federation versions, prefixed with an equals sign (=), for example '=2.9.3'. Alternatively, you can use 1 or 2 (without an equals sign) for the latest release of Federation 1 or 2 respectively.

rover dev \
  --graph-ref docs-example-graph@current \
  --supergraph-config federation_override.yaml
  --federation-version '=2.9.3'

If both a federation_override.yaml and the --federation-version option are used, --federation-version takes precedence.

Adding, removing, or updating subgraphs in a rover dev session

While running rover dev, it's possible to add, remove, and update subgraphs by updating the supergraph config file.

Health check

By default, the router's health check endpoint is disabled in rover dev. You can enable it again by enabling it in a router configuration YAML file and passing it to rover dev via the --router-config argument described in the following section.

Configuring the router

To configure advanced router functionality like CORS settings or header passthrough for subgraphs, you can pass a valid router configuration YAML file to rover dev via the --router-config <ROUTER_CONFIG_PATH> argument.

GraphOS Router features

If you want to use GraphOS Router features, you must provide both:

1 A graph API key either via the APOLLO_KEY environment variable or by configuring credentials in Rover.

1. A graph ref either via the APOLLO_GRAPH_REF environment variable or the --graph-ref option. Learn about the difference between these in the section below.

Understanding APOLLO_GRAPH_REF vs --graph-ref

While both the APOLLO_GRAPH_REF environment variable and --graph-ref option provide a graph ref to rover dev, they work slightly differently:

This means you should:

• Use APOLLO_GRAPH_REF environment variable when you are using local schema files for development and need to enable GraphOS Router features.

• Use the --graph-ref option when you want to develop against a published graph variant, pulling its schema from GraphOS. This option also enables GraphOS Router features if the referenced graph has access to them.

Federation 2 ELv2 license

The first time you use Federation 2 composition on a particular machine, Rover prompts you to accept the terms and conditions of the ELv2 license. On future invocations, Rover remembers that you already accepted the license and doesn't prompt you again (even if you update Rover).

Plugins

The ELv2-licensed plugins, supergraph (built from this source) and router (built from this source) are installed to ~/.rover/bin if you installed with the curl | sh installer, and to ./node_modules/.bin/ if you installed with npm.

Versioning

By default, rover dev uses the latest version of the router and composition plugins. The latest version for each is currently configured in the Rover GitHub repo, however, you can override either of these by setting the environment variables APOLLO_ROVER_DEV_COMPOSITION_VERSION=2.0.0 and APOLLO_ROVER_DEV_ROUTER_VERSION=1.0.0. If you already have these plugins installed, you can pass --skip-update to rover dev in order to keep the plugins at the same version.