Creating a Custom Apollo Router Core Binary

Learn how to compile a custom binary from Apollo Router Core source, which is required to create custom native Rust plugins for the router.

⚠️ Apollo doesn't recommend creating native plugins for the Apollo Router Core or GraphOS Router, for the following reasons:

• Native plugins require familiarity with programming in Rust.

• Native plugins require compiling a custom router binary from source, which can introduce unexpected behavior in your router that's difficult to diagnose and support.

Instead, for most router customizations, Apollo recommends creating either a Rhai script or an external coprocessor. Both of these customizations are supported by Apollo and provide strong separation of concerns and fault isolation.

If you must create a native plugin, please open a GitHub issue, and Apollo can investigate adding the custom capability to the stock router binary.

Prerequisites

To compile the router, you need to have Rust 1.85.0 or later installed.

1. Create a new project

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

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   1cargo new --bin starstuff

For the purposes of this tutorial, set your project's name to starstuff.

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

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   1cd starstuff

Write the source code for your custom binary.

2. Compile the router

Create a debug build of the router with the following command:

1cargo build

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

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

1cargo 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:

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   1curl -sSL https://supergraph.demo.starstuff.dev/ > supergraph-schema.graphql

2. Run the router and provide the example schema like so:

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   1cargo 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, implement your new plugin.

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

   YAML

   router.yaml

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   1plugins:
   2  starstuff.hello_world:
   3    message: "starting my plugin"

3. Run the router again:

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   1cargo run -- --hot-reload --config router.yaml --supergraph supergraph-schema.graphql

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

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   12022-05-21T09:16:33.160288Z  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.

Memory allocator

On Linux the apollo-router crate sets jemalloc as the global memory allocator for Rust to reduce memory fragmentation. Future versions may do so on more platforms, or switch to yet a different allocator. This is enabled by default and controlled by a global-allocator Cargo feature flag. If you want to choose a different allocator, disable it in your Cargo.toml:

1[dependencies]
2apollo-router = {version = "[…]", default-features = false}

If you make a library crate, also specify default-features = false in order to leave the choice open for the eventual executable crate. (Cargo default features are only disabled if all dependents specify default-features = false.)

Related topics

• Optimizing Custom Router Builds