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Creating a custom Apollo Router binary


To use custom plugins that aren't bundled with the default Apollo Router distribution, you need to compile your own custom router binary. This page walks you through creating that binary from scratch and adding a plugin to it.

Note: The Apollo Router is made available under the Elastic License v2.0 (ELv2). This applies to its source code and all distributions. For details, see our licensing page.

Prerequisites

To compile the Apollo Router, you need to have the following installed:

After you install the above, also install the cargo-xtask and cargo-scaffold crates:

cargo install cargo-xtask
cargo install cargo-scaffold

1. Create a new project

  1. Use the cargo-scaffold command to create a project for your custom router:

    cargo-scaffold scaffold https://github.com/apollographql/router.git -r apollo-router-scaffold/templates/base
  2. The cargo-scaffold command prompts you for some configuration settings. For the purposes of this tutorial, set your project's name to starstuff.

  3. After your project is created, change to the starstuff directory:

    cd starstuff

The generated project has the following layout:

starstuff
├── Cargo.toml # Dependencies are declared here
├── README.md
├── router.yaml # Router yaml config
├── src
│ ├── main.rs # Entry point
│ └── plugins # Custom plugins are located here
│ └── mod.rs
└── xtask # Build support files
├── Cargo.toml
└── src
└── main.rs

The Apollo Router uses an auto-discovery mechanism for plugins, so any plugins you add via dependency are automatically available to the Router at runtime.

2. Compile the router

Create a debug build of the Apollo Router with the following command:

cargo build

The resulting debug binary is located in target/debug/router.

To create a release build for production environments, use this command instead:

cargo build --release

The resulting release binary is now located in target/release/router.

3. Run the compiled binary

Now you can test out your compiled router with an example supergraph schema.

  1. Download the example schema with the following command:

    curl -sSL https://supergraph.demo.starstuff.dev/ > supergraph-schema.graphql
  2. Run the router and provide the example schema like so:

    cargo run -- --hot-reload --config router.yaml --supergraph supergraph-schema.graphql

    During development, it's helpful to use cargo run to run the router.

If you're using managed federation, you set the APOLLO_KEY and APOLLO_GRAPH_REF environment variables instead of specifying the supergraph schema as a file. For details, see this section.

4. Create a plugin

  1. From within your project directory, scaffold a new plugin with the following command:

    cargo router plugin create hello_world
  2. The command prompts you to choose a starting template:

    Select a plugin template:
    > "basic"
    "auth"
    "tracing"

    The available templates are:

    • basic - a barebones plugin
    • auth - an authentication plugin for making an external call
    • tracing - a telemetry plugin that adds a custom metric span and a log message

    For the purposes of this tutorial, choose basic.

  3. Add configuration options for the created plugin to your router.yaml file:

    router.yaml
    plugins:
    starstuff.hello_world:
    message: "starting my plugin"
  4. Run the router again:

    cargo run -- --hot-reload --config router.yaml --supergraph supergraph-schema.graphql

    This time, you should see a log line like the following:

    2022-05-21T09:16:33.160288Z INFO router::plugins::hello_world: starting my plugin

Nice work! You now have a custom router binary with an associated plugin. Next, you can extend the plugin with the functionality you need or add more plugins.

Removing a plugin

To remove a previously added plugin from your router project, use the following command:

cargo router plugin remove hello_world

Note that depending on the structure of your plugin, the command might fail to remove all of its associated files.

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