Configuring the Apollo Router

You run the Apollo Router with the following command (assuming you're in the same directory as the router executable):

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./router --config router.yaml --supergraph supergraph-schema.graphql

Arguments for this command are described below.

Environment variables

If you're using the Apollo Router with managed federation and GraphOS, set these environment variables in its startup command:

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APOLLO_KEY="..." APOLLO_GRAPH_REF="..." ./router

Command arguments

The router command supports the arguments listed in the table below.

Where indicated, some of these arguments can also be set via an environment variable. If you specify a configuration value using both mechanisms, the command-line argument's value takes precedence.

Config subcommand

YAML config file

The Apollo Router takes an optional YAML configuration file as input via the --config option:

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./router --config router.yaml

This file enables you to customize various aspects of your router's behavior, covered in the subsections below.

Listen address

By default, the Apollo Router starts an HTTP server that listens on 127.0.0.1:4000. You can specify a different address by setting supergraph.listen:

IPv4

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supergraph:
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  # The socket address and port to listen on
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  listen: 127.0.0.1:4000

IPv6

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supergraph:
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  # The socket address and port to listen on. 
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  # Note that this must be quoted to avoid interpretation as an array in YAML.
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  listen: '[::1]:4000'

Unix socket

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supergraph:
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  # Absolute path to a Unix socket
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  listen: /tmp/router.sock

Endpoint path

By default, the router starts an HTTP server that exposes a POST/GET endpoint at path /.

You can specify a different path by setting supergraph.path:

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supergraph:
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  # The path for GraphQL execution
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  # (Defaults to /)
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  path: /graphql

The path must start with /.

Path parameters and wildcards are supported. For example:

• /:my_dynamic_prefix/graphql matches both /my_project_a/graphql and /my_project_b/graphql.
• /graphql/* matches /graphql/my_project_a and /graphql/my_project_b.
• /g* matches /graphql and /gateway.

Introspection

By default, the router does not resolve introspection queries. You can enable introspection like so:

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# Do not enable introspection in production!
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supergraph:
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  introspection: true

Landing pages

The Apollo Router can serve any of the following landing pages to browsers that visit its endpoint path:

• A basic landing page that displays an example query curl command (default)

  YAML

  router.yaml

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  # This is the default behavior. You don't need to include this config.
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  homepage:
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    enabled: true

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• No landing page

  YAML

  router.yaml

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  homepage:
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    enabled: false

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• Apollo Sandbox, which enables you to explore your schema and compose operations against it using the Explorer

  Note the additional configuration required to use Sandbox:

  YAML

  router.yaml

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  sandbox:
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    enabled: true
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  # Sandbox uses introspection to obtain your router's schema.
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  supergraph:
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    introspection: true
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  # Sandbox requires the default landing page to be disabled.
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  homepage:
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    enabled: false

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  ⚠️ Do not enable Sandbox in production! Sandbox requires enabling introspection, which is strongly discouraged in production environments.

Subgraph routing URLs

By default, the Apollo Router obtains the routing URL for each of your subgraphs from the composed supergraph schema you provide it. In most cases, no additional configuration is required.

However, if you do need to override a particular subgraph's routing URL (for example, to handle changing network topography), you can do so with the override_subgraph_url option:

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override_subgraph_url:
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  accounts: http://localhost:8080

In this example, the accounts subgraph URL is overridden to point to http://localhost:8080. The URL specified in the supergraph schema is ignored.

Any subgraphs that are omitted from override_subgraph_url continue to use the routing URL specified in the supergraph schema.

Caching

By default, the Apollo Router stores the following data in its in-memory cache to improve performance:

• Generated query plans
• Automatic persisted queries (APQ)
• Introspection responses

You can configure certain caching behaviors for generated query plans and APQ (but not introspection responses). For details, see In-memory caching in the Apollo Router.

If you have a GraphOS Enterprise plan, you can also configure a Redis-backed distributed cache that enables multiple router instances to share cached values. For details, see Distributed caching in the Apollo Router

HTTP header rules

See Sending HTTP headers to subgraphs.

Cross-Origin Resource Sharing (CORS)

See Configuring CORS in the Apollo Router.

Defer support

See Apollo Router support for @defer.

External coprocessing

See External coprocessing in the Apollo Router.

OpenTelemetry tracing

See Tracing in the Apollo Router.

TLS

TLS connections to subgraphs are verified using the list of certificate authorities provided by the system. You can override this list with a combination of global and per-subgraph settings:

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tls:
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  subgraph:
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    # Use these certificate authorities unless overridden per-subgraph
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    all:
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      certificate_authorities: "${file./path/to/ca.crt}"
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    # Override global setting for individual subgraphs
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    subgraphs:
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      products:
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        certificate_authorities: "${file./path/to/product_ca.crt}"

Plugins

You can customize the Apollo Router's behavior with plugins. Each plugin can have its own section in the configuration file with arbitrary values:

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plugins:
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  example.plugin:
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    var1: "hello"
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    var2: 1

Variable expansion

You can reference variables directly in your YAML config file. This is useful for referencing secrets without including them in the file.

Currently, the Apollo Router supports expansion of environment variables and file paths. Corresponding variables must be prefixed with env. or file.

The router uses Unix-style expansion. Here are some examples:

• ${env.ENV_VAR_NAME} expands to the value of environment variable ENV_VAR_NAME.
• ${env.ENV_VAR_NAME:-some_default} expands to the value of environment variable ENV_VAR_NAME, or falls back to the value some_default if the environment variable is not defined.
• ${file.a.txt} expands to the contents of the file a.txt.
• ${file.a.txt:-some_default} expands to the contents of the file a.txt, or falls back to the value some_default if the file does not exist.

Variable expansions are valid only for YAML values, not keys:

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supergraph:
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  listen: "${env.MY_LISTEN_ADDRESS}" 
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example:
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  password: "${env.MY_PASSWORD}" 

Reusing configuration

You can reuse parts of your configuration file in multiple places using standard YAML aliasing syntax:

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headers:
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  subgraphs:
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    products:
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      request:
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        - insert: &insert_custom_header
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            name: "custom-header"
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            value: "something"
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    reviews:
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      request:
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        - insert: *insert_custom_header

Here, the name and value entries under &insert_custom_header are reused under *insert_custom_header.

Configuration awareness in your text editor

The Apollo Router can generate a JSON schema for config validation in your text editor. This schema helps you format the YAML file correctly and also provides content assist.

Generate the schema with the following command:

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./router config schema > configuration_schema.json

After you generate the schema, configure your text editor. Here are the instructions for some commonly used editors:

• Visual Studio Code
• Emacs
• IntelliJ
• Sublime
• Vim

Upgrading your router configuration

New releases of the Apollo Router might introduce breaking changes to the YAML config file's expected format, usually to extend existing functionality or improve usability.

If you run a new version of your router with a configuration file that it no longer supports:

1. The router emits a warning on startup.
2. The router attempts to translate your provided configuration to the new expected format.
   • If the translation succeeds without errors, the router starts up as usual.
   • If the translation fails, the router terminates.

If you encounter this warning, you can use the router config upgrade command to see the new expected format for your existing configuration file:

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./router config upgrade <path_to_router.yaml>

You can also view a diff of exactly which changes are necessary to upgrade your existing configuration file:

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./router config upgrade --diff <path_to_router.yaml>