mirror of
https://github.com/navidrome/navidrome.git
synced 2026-10-21 16:57:14 +02:00
98555ca499
Adds db/pglite, a bridge that runs the PGlite WASI build of PostgreSQL 17.5 inside the Navidrome process with wazero and exposes it to database/sql through pgx over the real wire protocol. Selected with DbPath = "pglite://<dir>". The bridge handles what the WASI build cannot do on its own: it emulates dup2 onto stdin (wazero refuses fd_renumber on preopens), replays ParameterStatus for connections after the first, synthesizes a missing ReadyForQuery after an error, recovers from the trap every PG ERROR raises, and passes wire bytes through shared wasm memory instead of files (round-trip floor 377 µs to 39 µs). Several connections are accepted and serialized onto the single backend, holding the session across a whole transaction and a whole handshake; a client that disconnects mid-transaction gets a ROLLBACK. db.go opens the pglite:// scheme, skips the SQLite-only migrations, and can apply a translated schema from ND_PGLITE_SCHEMA. The shared count() helper now adds its ORDER BY only for SQLite, since Postgres rejects it next to count(distinct ...). The wasm archive is not committed. The README explains how to build it and lists the limits found: one session, one process (DevExternalScanner must be off), shared session state, simple protocol only.
125 lines
3.1 KiB
Go
125 lines
3.1 KiB
Go
package pglite
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import (
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"context"
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"io"
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"os"
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"path/filepath"
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"sync"
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"github.com/tetratelabs/wazero"
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"github.com/tetratelabs/wazero/api"
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"github.com/tetratelabs/wazero/experimental"
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"github.com/tetratelabs/wazero/imports/wasi_snapshot_preview1"
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)
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const errnoNotsup = 58
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// switchableStdin is the guest's stdin. PGlite runs initdb by dup2()-ing a script file onto
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// fd 0, which wazero refuses for preopens, so we emulate it by swapping the reader instead.
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type switchableStdin struct {
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mu sync.Mutex
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r io.ReadCloser
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}
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func (s *switchableStdin) Read(p []byte) (int, error) {
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s.mu.Lock()
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defer s.mu.Unlock()
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if s.r == nil {
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return 0, io.EOF
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}
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return s.r.Read(p)
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}
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func (s *switchableStdin) set(path string) error {
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f, err := os.Open(path)
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if err != nil {
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return err
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}
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s.mu.Lock()
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defer s.mu.Unlock()
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if s.r != nil {
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_ = s.r.Close()
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}
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s.r = f
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return nil
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}
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func (s *switchableStdin) Close() error {
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s.mu.Lock()
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defer s.mu.Unlock()
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if s.r != nil {
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err := s.r.Close()
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s.r = nil
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return err
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}
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return nil
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}
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// fdTracker listens to path_open so fd_renumber can resolve a guest fd back to a host path.
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type fdTracker struct {
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mounts map[int32]string // preopen fd -> host dir
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opened map[int32]string // guest fd -> host path
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pending string
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outPtr uint32
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pathBad bool
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}
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func newFDTracker(mounts ...string) *fdTracker {
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t := &fdTracker{mounts: map[int32]string{}, opened: map[int32]string{}}
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for i, m := range mounts {
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t.mounts[int32(3+i)] = m
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}
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return t
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}
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func (t *fdTracker) NewFunctionListener(def api.FunctionDefinition) experimental.FunctionListener {
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if def.ModuleName() == wasi_snapshot_preview1.ModuleName && def.Name() == "path_open" {
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return t
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}
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return nil
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}
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func (t *fdTracker) Before(_ context.Context, mod api.Module, _ api.FunctionDefinition, params []uint64, _ experimental.StackIterator) {
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dir, ok := t.mounts[int32(params[0])]
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path, okMem := mod.Memory().Read(uint32(params[2]), uint32(params[3]))
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t.pathBad = !ok || !okMem
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if !t.pathBad {
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t.pending = filepath.Join(dir, string(path))
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}
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t.outPtr = uint32(params[8])
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}
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func (t *fdTracker) After(_ context.Context, mod api.Module, _ api.FunctionDefinition, results []uint64) {
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if t.pathBad || results[0] != 0 {
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return
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}
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if fd, ok := mod.Memory().ReadUint32Le(t.outPtr); ok {
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t.opened[int32(fd)] = t.pending
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}
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}
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func (t *fdTracker) Abort(context.Context, api.Module, api.FunctionDefinition, error) {}
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// instantiateWASI installs wasi_snapshot_preview1 with fd_renumber(fd, 0) emulated via stdin.
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func instantiateWASI(ctx context.Context, r wazero.Runtime, tracker *fdTracker, stdin *switchableStdin) error {
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b := r.NewHostModuleBuilder(wasi_snapshot_preview1.ModuleName)
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wasi_snapshot_preview1.NewFunctionExporter().ExportFunctions(b)
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b.NewFunctionBuilder().
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WithFunc(func(_ context.Context, _ api.Module, from, to int32) int32 {
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if to != 0 {
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return errnoNotsup
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}
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path, ok := tracker.opened[from]
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if !ok {
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return errnoNotsup
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}
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if err := stdin.set(path); err != nil {
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return errnoNotsup
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}
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return 0
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}).
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Export("fd_renumber")
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_, err := b.Instantiate(ctx)
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return err
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}
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