subgraphs.mdx

title	description
Rover subgraph commands	For use with Apollo Federation

A subgraph is a graph that contributes to the composition of a federated supergraph:

graph BT;
  gateway(["Supergraph (A + B + C)"]);
  serviceA[Subgraph A];
  serviceB[Subgraph B];
  serviceC[Subgraph C];
  gateway --- serviceA & serviceB & serviceC;

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Rover commands that interact with subgraphs begin with rover subgraph.

Fetching a subgraph schema

These commands enable you to fetch the schema for a single subgraph in a federated graph. To instead fetch the API schema for a supergraph, use rover graph fetch. To fetch the supergraph schema, use rover supergraph fetch.

subgraph fetch

This command requires authenticating Rover with Apollo Studio.

You can use Rover to fetch the current schema of any subgraph that belongs to a Studio graph and variant that Rover has access to.

Run the subgraph fetch command, like so:

rover subgraph fetch my-graph@my-variant --name accounts

The argument my-graph@my-variant in the example above is a graph ref that specifies the ID of the Studio graph you're fetching from, along with which variant you're fetching.

You can omit @ and the variant name. If you do, Rover uses the default variant, named current.

The --name option is required. It specifies which subgraph you're fetching the schema for.

subgraph introspect

If you need to obtain a running subgraph's schema, you can use Rover to execute an enhanced introspection query on it. This is especially helpful if the subgraph doesn't define its schema via SDL (as is the case with graphql-kotlin).

Use the subgraph introspect command, like so:

rover subgraph introspect http://localhost:4001

The subgraph must be reachable by Rover. The subgraph does not need to have introspection enabled.

Unlike a standard introspection query, the result of rover subgraph introspect does include certain directives (specifically, directives related to federation like @key). This is possible because the command uses a separate introspection mechanism provided by the Apollo Federation subgraph specification.

Watching for schema changes

If you pass --watch to rover subgraph introspect, Rover introspects your subgraph every second. Whenever the returned schema differs from the previously returned schema, Rover outputs the updated schema. This is most useful when combined with the --output <OUTPUT_FILE> argument which will write the introspection response out to a file whenever its contents change.

Including headers

If the endpoint you're trying to reach requires HTTP headers, you can use the --header (-H) flag to pass key:value pairs of headers. If you have multiple headers to pass, provide the flag multiple times. If a header includes any spaces, the pair must be quoted.

rover subgraph introspect http://localhost:4001 --header "Authorization: Bearer token329r"

Output format

rover subgraph introspect http://localhost:4001\
  | rover subgraph publish my-graph@dev\
  --schema - --name accounts\
  --routing-url https://my-running-subgraph.com/api

By default, both subgraph fetch and subgraph introspect output fetched SDL to stdout. This is useful for providing the schema as input to other Rover commands:

rover subgraph introspect http://localhost:4000 | rover subgraph check my-graph --schema -

You can also save the output to a local .graphql file like so:

# Creates accounts-schema.graphql or overwrites if it already exists
rover subgraph introspect http://localhost:4000 --output accounts-schema.graphql

For more on passing values via stdout, see Using stdout.

Listing subgraphs in a supergraph

subgraph list

This command requires authenticating Rover with Apollo Studio.

You can use the subgraph list to list all of a particular supergraph's available subgraphs in Apollo Studio:

rover subgraph list my-supergraph@staging

This command lists all subgraphs for the specified variant, including their routing URLs and when they were last updated (in local time). A link to view this information in Apollo Studio is also provided.

Subgraphs:

+----------+-------------- --------------+----------------------------+
| Name     | Routing Url                 | Last Updated               |
+----------+-----------------------------+----------------------------+
| reviews  | https://reviews.my-app.com  | 2020-10-21 12:23:28 -04:00 |
+----------+----------------------------------------+-----------------+
| books    | https://books.my-app.com    | 2020-09-20 13:58:27 -04:00 |
+----------+----------------------------------------+-----------------+
| accounts | https://accounts.my-app.com | 2020-09-20 12:23:36 -04:00 |
+----------+----------------------------------------+-----------------+
| products | https://products.my-app.com | 2020-09-20 12:23:28 -04:00 |
+----------+----------------------------------------+-----------------+

View full details at https://studio.apollographql.com/graph/my-supergraph/service-list

Publishing a subgraph schema to Apollo Studio

subgraph publish

This command requires authenticating Rover with Apollo Studio.

You can use Rover to publish schema changes to a subgraph in one of your GraphOS-managed supergraphs.

Use the subgraph publish command, like so:

rover subgraph publish my-supergraph@my-variant \
  --schema "./accounts/schema.graphql" \
  --name accounts \
  --routing-url "https://my-running-subgraph.com/api"

The argument my-supergraph@my-variant in the example above is a graph ref that specifies the ID of the Studio graph you're publishing to, along with which variant you're publishing to.

You can omit @ and the variant name. If you do, Rover publishes the schema to the default variant, named current.

If the graph exists in the graph registry but the variant does not, a new variant is created on publish.

Options include:

Name	Description
--schema	Required. The path to a local .graphql or .gql file, in SDL format. Alternatively, you can provide -, in which case the command uses an SDL string piped to stdin instead (see Using stdin).
--name	Required. The name of the subgraph to publish to. Every subgraph name must: Begin with a letter (capital or lowercase) Include only letters, numbers, underscores (_), and hyphens (-) Have a maximum of 64 characters
--routing-url	The URL that your supergraph uses to communicate with the subgraph in a managed federation architecture. Required the first time you publish a particular subgraph. Provide an empty string if your subgraph isn't deployed yet, or if you aren't using managed federation. Optional after your first publish. Provide only if you need to change the subgraph's routing URL.
--convert	If a monolithic schema for this variant already exists in the graph registry instead of multiple subgraph schemas, you need to run rover subgraph publish with the --convert flag to convert this variant to a federated graph with one or more subgraphs. This permanently deletes the monolithic schema from this variant and replaces it with a single subgraph. In many cases, you need to run subgraph publish for multiple or all of your subgraphs before Studio can successfully compose a supergraph schema. This option has no effect if you publish to a non-monolithic variant.

Checking subgraph schema changes

subgraph check

This command requires authenticating Rover with Apollo Studio.

Before you publish subgraph schema changes to Apollo Studio, you can check those changes to confirm that you aren't introducing breaking changes to your application clients.

To do so, you can run the subgraph check command:

# using a schema file
rover subgraph check my-graph@my-variant --schema ./schema.graphql --name accounts

# using piped input to stdin
rover subgraph introspect http://localhost:4000 \
  | rover subgraph check my-graph@my-variant \
  --schema - --name accounts

As shown, arguments and options are similar to subgraph publish.

To configure the behavior of schema checks (such as the time range of past operations to check against), see the documentation for schema checks.

If you don't want to wait for the check to complete, you can run the command with the --background flag. You can then look up the check's result in Apollo Studio on the Checks tab.

Running checks in CI

If you're running schema checks in CI, you might want to pass the --background flag to rover subgraph check. This flag instructs Rover to initiate schema checks but not await their result. If you've connected Apollo Studio to your GitHub repository, the integration detects the checks execution and adds a status to the associated pull request.

Deleting a subgraph

subgraph delete

This command requires authenticating Rover with Apollo Studio.

You can delete a single subgraph from a federated variant by running rover subgraph delete:

# ⚠️ This action is irreversible!
rover subgraph delete my-graph@my-variant --name subgraph-to-delete

This command prompts you for confirmation because the action is irreversible. You can bypass confirmation by passing the --confirm flag.

This command fails with an error if any other subgraph references types that originate in this subgraph.

To delete an entire federated graph instead of a single subgraph, see Deleting a variant.