feat(tvix/nar-bridge): init

This provides a Nix HTTP Binary Cache interface in front of a tvix-store
that's reachable via gRPC.

TODOs:

 - remove import command, move serve up to toplevel. We have nix-copy-
   closure and tvix-store commands.
 - loop into CI. We should be able to fetch the protos as a third-party
   dependency.
 - Check if we can test nar-bridge slightly easier in an integration
   test.
 - Ensure we support connecting to unix sockets and grpc+http at least,
   using the same syntax as tvix-store.
 - Don't buffer the entire blob when rendering NAR

Co-Authored-By: Connor Brewster <cbrewster@hey.com>
Co-Authored-By: Márton Boros <martonboros@gmail.com>
Co-Authored-By: Vo Minh Thu <noteed@gmail.com>

Change-Id: I6064474e49dfe78cea67676957462d9f28658d4a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9339
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/nar-bridge/pkg/server/server.go

@@ -0,0 +1,86 @@
+package server
+
+import (
+	"fmt"
+	"net/http"
+	"sync"
+	"time"
+
+	storev1pb "code.tvl.fyi/tvix/store/protos"
+	"github.com/go-chi/chi/middleware"
+	"github.com/go-chi/chi/v5"
+	log "github.com/sirupsen/logrus"
+)
+
+type Server struct {
+	handler chi.Router
+
+	directoryServiceClient storev1pb.DirectoryServiceClient
+	blobServiceClient      storev1pb.BlobServiceClient
+	pathInfoServiceClient  storev1pb.PathInfoServiceClient
+
+	// When uploading NAR files to a HTTP binary cache, the .nar
+	// files are uploaded before the .narinfo files.
+	// We need *both* to be able to fully construct a PathInfo object.
+	// Keep a in-memory map of narhash(es) (in SRI) to sparse PathInfo.
+	// This is necessary until we can ask a PathInfoService for a node with a given
+	// narSha256.
+	narHashToPathInfoMu sync.Mutex
+	narHashToPathInfo   map[string]*storev1pb.PathInfo
+}
+
+func New(
+	directoryServiceClient storev1pb.DirectoryServiceClient,
+	blobServiceClient storev1pb.BlobServiceClient,
+	pathInfoServiceClient storev1pb.PathInfoServiceClient,
+	enableAccessLog bool,
+	priority int,
+) *Server {
+	r := chi.NewRouter()
+
+	if enableAccessLog {
+		r.Use(middleware.Logger)
+	}
+
+	r.Get("/", func(w http.ResponseWriter, r *http.Request) {
+		_, err := w.Write([]byte("nar-bridge"))
+		if err != nil {
+			log.Errorf("Unable to write response: %v", err)
+		}
+	})
+
+	r.Get("/nix-cache-info", func(w http.ResponseWriter, r *http.Request) {
+		_, err := w.Write([]byte(fmt.Sprintf("StoreDir: /nix/store\nWantMassQuery: 1\nPriority: %d\n", priority)))
+		if err != nil {
+			log.Errorf("Unable to write response: %v", err)
+		}
+	})
+
+	s := &Server{
+		handler:                r,
+		directoryServiceClient: directoryServiceClient,
+		blobServiceClient:      blobServiceClient,
+		pathInfoServiceClient:  pathInfoServiceClient,
+		narHashToPathInfo:      make(map[string]*storev1pb.PathInfo),
+	}
+
+	registerNarPut(s)
+	registerNarinfoPut(s)
+
+	registerNarinfoGet(s)
+	registerNarGet(s)
+
+	return s
+}
+
+func (s *Server) ListenAndServe(addr string) error {
+	srv := &http.Server{
+		Addr:         addr,
+		Handler:      s.handler,
+		ReadTimeout:  50 * time.Second,
+		WriteTimeout: 100 * time.Second,
+		IdleTimeout:  150 * time.Second,
+	}
+
+	return srv.ListenAndServe()
+}