feat(tvix/nar-bridge): init

This adds an implementation of nar-bridge in Rust.
Currently, only the GET parts are implemented.

Contrary to the Go variant, this doesn't try to keep a mapping from nar
hashes to root node in memory, it simply encodes the root node itself
(stripped by its basename) into the URL.

This pulls in a more recent version of axum than what we use in
tonic, causing two versions of http and hyper, however dealing with
`Body::from_stream` in axum 0.6 is much more annoying, and
https://github.com/hyperium/tonic/pull/1740 suggests this will be fixed
soon.

Change-Id: Ia4c2dbda7cd3fdbe47a75f3e33544d19eac6e44e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11898
Autosubmit: flokli <flokli@flokli.de>
Reviewed-by: Brian Olsen <me@griff.name>
Tested-by: BuildkiteCI

tvix/nar-bridge/src/bin/nar-bridge.rs

@@ -0,0 +1,84 @@
+use clap::Parser;
+use nar_bridge::AppState;
+use tracing::info;
+
+/// Expose the Nix HTTP Binary Cache protocol for a tvix-store.
+#[derive(Parser)]
+#[command(author, version, about, long_about = None)]
+struct Cli {
+    #[arg(long, env, default_value = "grpc+http://[::1]:8000")]
+    blob_service_addr: String,
+
+    #[arg(long, env, default_value = "grpc+http://[::1]:8000")]
+    directory_service_addr: String,
+
+    #[arg(long, env, default_value = "grpc+http://[::1]:8000")]
+    path_info_service_addr: String,
+
+    /// The priority to announce at the `nix-cache-info` endpoint.
+    /// A lower number means it's *more preferred.
+    #[arg(long, env, default_value_t = 39)]
+    priority: u64,
+
+    /// The address to listen on.
+    #[clap(flatten)]
+    listen_args: tokio_listener::ListenerAddressLFlag,
+
+    #[cfg(feature = "otlp")]
+    /// Whether to configure OTLP. Set --otlp=false to disable.
+    #[arg(long, default_missing_value = "true", default_value = "true", num_args(0..=1), require_equals(true), action(clap::ArgAction::Set))]
+    otlp: bool,
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    let cli = Cli::parse();
+
+    let _tracing_handle = {
+        #[allow(unused_mut)]
+        let mut builder = tvix_tracing::TracingBuilder::default();
+        #[cfg(feature = "otlp")]
+        {
+            if cli.otlp {
+                builder = builder.enable_otlp("tvix.store");
+            }
+        }
+        builder.build()?
+    };
+
+    // initialize stores
+    let (blob_service, directory_service, path_info_service, _nar_calculation_service) =
+        tvix_store::utils::construct_services(
+            cli.blob_service_addr,
+            cli.directory_service_addr,
+            cli.path_info_service_addr,
+        )
+        .await?;
+
+    let state = AppState::new(blob_service, directory_service, path_info_service.into());
+
+    let app = nar_bridge::gen_router(cli.priority).with_state(state);
+
+    let listen_address = &cli.listen_args.listen_address.unwrap_or_else(|| {
+        "[::]:8000"
+            .parse()
+            .expect("invalid fallback listen address")
+    });
+
+    let listener = tokio_listener::Listener::bind(
+        listen_address,
+        &Default::default(),
+        &cli.listen_args.listener_options,
+    )
+    .await?;
+
+    info!(listen_address=%listen_address, "starting daemon");
+
+    tokio_listener::axum07::serve(
+        listener,
+        app.into_make_service_with_connect_info::<tokio_listener::SomeSocketAddrClonable>(),
+    )
+    .await?;
+
+    Ok(())
+}