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>
This commit is contained in:
Florian Klink
flokli
parent
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commit
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27 changed files with 2663 additions and 0 deletions
278
tvix/nar-bridge/pkg/writer/writer.go
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278
tvix/nar-bridge/pkg/writer/writer.go
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package writer
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import (
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"fmt"
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"io"
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"path"
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storev1pb "code.tvl.fyi/tvix/store/protos"
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"github.com/nix-community/go-nix/pkg/nar"
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)
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type DirectoryLookupFn func([]byte) (*storev1pb.Directory, error)
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type BlobLookupFn func([]byte) (io.ReadCloser, error)
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// Export will traverse a given pathInfo structure, and write the contents
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// in NAR format to the passed Writer.
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// It uses directoryLookupFn and blobLookupFn to resolve references.
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func Export(
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w io.Writer,
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pathInfo *storev1pb.PathInfo,
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directoryLookupFn DirectoryLookupFn,
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blobLookupFn BlobLookupFn,
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) error {
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// initialize a NAR writer
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narWriter, err := nar.NewWriter(w)
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if err != nil {
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return fmt.Errorf("unable to initialize nar writer: %w", err)
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}
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defer narWriter.Close()
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// populate rootHeader
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rootHeader := &nar.Header{
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Path: "/",
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}
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// populate a stack
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// we will push paths and directories to it when entering a directory,
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// and emit individual elements to the NAR writer, draining the Directory object.
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// once it's empty, we can pop it off the stack.
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var stackPaths = []string{}
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var stackDirectories = []*storev1pb.Directory{}
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// peek at the pathInfo root and assemble the root node and write to writer
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// in the case of a regular file, we retrieve and write the contents, close and exit
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// in the case of a symlink, we write the symlink, close and exit
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switch v := (pathInfo.GetNode().GetNode()).(type) {
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case *storev1pb.Node_File:
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rootHeader.Type = nar.TypeRegular
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rootHeader.Size = int64(v.File.GetSize())
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rootHeader.Executable = v.File.GetExecutable()
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err := narWriter.WriteHeader(rootHeader)
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if err != nil {
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return fmt.Errorf("unable to write root header: %w", err)
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}
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// if it's a regular file, retrieve and write the contents
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contentReader, err := blobLookupFn(v.File.GetDigest())
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if err != nil {
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return fmt.Errorf("unable to lookup blob: %w", err)
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}
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defer contentReader.Close()
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_, err = io.Copy(narWriter, contentReader)
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if err != nil {
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return fmt.Errorf("unable to copy contents from contentReader: %w", err)
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}
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err = contentReader.Close()
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if err != nil {
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return fmt.Errorf("unable to close content reader: %w", err)
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}
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err = narWriter.Close()
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if err != nil {
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return fmt.Errorf("unable to close nar reader: %w", err)
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}
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return nil
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case *storev1pb.Node_Symlink:
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rootHeader.Type = nar.TypeSymlink
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rootHeader.LinkTarget = string(v.Symlink.GetTarget())
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err := narWriter.WriteHeader(rootHeader)
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if err != nil {
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return fmt.Errorf("unable to write root header: %w", err)
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}
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err = narWriter.Close()
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if err != nil {
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return fmt.Errorf("unable to close nar reader: %w", err)
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}
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return nil
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case *storev1pb.Node_Directory:
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// We have a directory at the root, look it up and put in on the stack.
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directory, err := directoryLookupFn(v.Directory.Digest)
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if err != nil {
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return fmt.Errorf("unable to lookup directory: %w", err)
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}
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stackDirectories = append(stackDirectories, directory)
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stackPaths = append(stackPaths, "/")
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err = narWriter.WriteHeader(&nar.Header{
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Path: "/",
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Type: nar.TypeDirectory,
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})
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if err != nil {
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return fmt.Errorf("error writing header: %w", err)
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}
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}
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// as long as the stack is not empty, we keep running.
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for {
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if len(stackDirectories) == 0 {
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return nil
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}
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// Peek at the current top of the stack.
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topOfStack := stackDirectories[len(stackDirectories)-1]
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topOfStackPath := stackPaths[len(stackPaths)-1]
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// get the next element that's lexicographically smallest, and drain it from
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// the current directory on top of the stack.
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nextNode := drainNextNode(topOfStack)
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// If nextNode returns nil, there's nothing left in the directory node, so we
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// can emit it from the stack.
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// Contrary to the import case, we don't emit the node popping from the stack, but when pushing.
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if nextNode == nil {
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// pop off stack
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stackDirectories = stackDirectories[:len(stackDirectories)-1]
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stackPaths = stackPaths[:len(stackPaths)-1]
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continue
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}
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switch n := (nextNode).(type) {
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case *storev1pb.DirectoryNode:
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err := narWriter.WriteHeader(&nar.Header{
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Path: path.Join(topOfStackPath, string(n.GetName())),
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Type: nar.TypeDirectory,
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})
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if err != nil {
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return fmt.Errorf("unable to write nar header: %w", err)
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}
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d, err := directoryLookupFn(n.GetDigest())
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if err != nil {
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return fmt.Errorf("unable to lookup directory: %w", err)
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}
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// add to stack
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stackDirectories = append(stackDirectories, d)
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stackPaths = append(stackPaths, path.Join(topOfStackPath, string(n.GetName())))
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case *storev1pb.FileNode:
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err := narWriter.WriteHeader(&nar.Header{
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Path: path.Join(topOfStackPath, string(n.GetName())),
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Type: nar.TypeRegular,
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Size: int64(n.GetSize()),
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Executable: n.GetExecutable(),
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})
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if err != nil {
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return fmt.Errorf("unable to write nar header: %w", err)
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}
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// copy file contents
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contentReader, err := blobLookupFn(n.GetDigest())
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if err != nil {
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return fmt.Errorf("unable to get blob: %w", err)
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}
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defer contentReader.Close()
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_, err = io.Copy(narWriter, contentReader)
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if err != nil {
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return fmt.Errorf("unable to copy contents from contentReader: %w", err)
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}
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err = contentReader.Close()
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if err != nil {
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return fmt.Errorf("unable to close content reader: %w", err)
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}
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case *storev1pb.SymlinkNode:
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err := narWriter.WriteHeader(&nar.Header{
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Path: path.Join(topOfStackPath, string(n.GetName())),
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Type: nar.TypeSymlink,
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LinkTarget: string(n.GetTarget()),
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})
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if err != nil {
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return fmt.Errorf("unable to write nar header: %w", err)
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}
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}
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}
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}
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// TODO: add validation functions to Directory in both rust and golang, to
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// validate the keys in directories, files and symlinks are sorted.
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// drainNextNode will drain a directory message with one of its child nodes,
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// whichever comes first alphabetically.
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func drainNextNode(d *storev1pb.Directory) interface{} {
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switch v := (smallestNode(d)).(type) {
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case *storev1pb.DirectoryNode:
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d.Directories = d.Directories[1:]
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return v
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case *storev1pb.FileNode:
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d.Files = d.Files[1:]
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return v
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case *storev1pb.SymlinkNode:
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d.Symlinks = d.Symlinks[1:]
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return v
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case nil:
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return nil
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default:
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panic("invalid type encountered")
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}
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}
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// smallestNode will return the node from a directory message,
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// whichever comes first alphabetically.
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func smallestNode(d *storev1pb.Directory) interface{} {
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childDirectories := d.GetDirectories()
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childFiles := d.GetFiles()
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childSymlinks := d.GetSymlinks()
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if len(childDirectories) > 0 {
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if len(childFiles) > 0 {
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if len(childSymlinks) > 0 {
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// directories,files,symlinks
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return smallerNode(smallerNode(childDirectories[0], childFiles[0]), childSymlinks[0])
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} else {
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// directories,files,!symlinks
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return smallerNode(childDirectories[0], childFiles[0])
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}
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} else {
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// directories,!files
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if len(childSymlinks) > 0 {
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// directories,!files,symlinks
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return smallerNode(childDirectories[0], childSymlinks[0])
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} else {
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// directories,!files,!symlinks
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return childDirectories[0]
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}
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}
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} else {
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// !directories
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if len(childFiles) > 0 {
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// !directories,files
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if len(childSymlinks) > 0 {
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// !directories,files,symlinks
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return smallerNode(childFiles[0], childSymlinks[0])
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} else {
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// !directories,files,!symlinks
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return childFiles[0]
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}
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} else {
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//!directories,!files
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if len(childSymlinks) > 0 {
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//!directories,!files,symlinks
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return childSymlinks[0]
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} else {
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//!directories,!files,!symlinks
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return nil
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}
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}
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}
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}
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// smallerNode compares two nodes by their name,
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// and returns the one with the smaller name.
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// both nodes may not be nil, we do check for these cases in smallestNode.
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func smallerNode(a interface{ GetName() []byte }, b interface{ GetName() []byte }) interface{ GetName() []byte } {
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if string(a.GetName()) < string(b.GetName()) {
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return a
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} else {
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return b
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}
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}
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