mmm: read-only mode.

eventstore/cmd/eventstore/main.go

@@ -86,7 +86,8 @@ var app = &cli.Command{
 			end = db.Close
 		case "mmm":
 			var err error
-			if db, err, end = doMmmInit(path); err != nil {
+			readonly := c.Args().First() == "query" || c.Args().First() == "count"
+			if db, err, end = doMmmInit(path, readonly); err != nil {
 				if end != nil {
 					end()
 				}

eventstore/cmd/eventstore/main_mmm.go

@@ -11,13 +11,14 @@ import (
 	"github.com/rs/zerolog"
 )
 
-func doMmmInit(path string) (eventstore.Store, error, func()) {
+func doMmmInit(path string, readonly bool) (eventstore.Store, error, func()) {
 	logger := zerolog.New(zerolog.NewConsoleWriter(func(w *zerolog.ConsoleWriter) {
 		w.Out = os.Stderr
 	}))
 	mmmm := mmm.MultiMmapManager{
 		Dir:      filepath.Dir(path),
 		Logger:   &logger,
+		ReadOnly: readonly,
 	}
 	if err := mmmm.Init(); err != nil {
 		return nil, err, nil

eventstore/mmm/delete.go

@@ -11,6 +11,10 @@ import (
 )
 
 func (il *IndexingLayer) DeleteEvent(id nostr.ID) error {
+	if il.mmmm.ReadOnly {
+		return ReadOnly
+	}
+
 	il.mmmm.writeMutex.Lock()
 	defer il.mmmm.writeMutex.Unlock()
 

eventstore/mmm/mmmm.go

@@ -2,6 +2,7 @@ package mmm
 
 import (
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -20,9 +21,12 @@ type mmap []byte
 
 func (_ mmap) String() string { return "<memory-mapped file>" }
 
+var ReadOnly = errors.New("mmm in read-only mode")
+
 type MultiMmapManager struct {
 	Dir      string
 	Logger   *zerolog.Logger
+	ReadOnly bool
 
 	layers IndexingLayers
 
@@ -62,6 +66,7 @@ func (b *MultiMmapManager) Init() error {
 		return fmt.Errorf("failed to create directory %s: %w", dbpath, err)
 	}
 
+	if !b.ReadOnly {
 		// create lockfile to prevent multiple instances
 		lockfilePath := filepath.Join(b.Dir, "mmmm.lock")
 		if _, err := os.OpenFile(lockfilePath, os.O_CREATE|os.O_EXCL|os.O_RDWR, 0644); err != nil {
@@ -70,6 +75,7 @@ func (b *MultiMmapManager) Init() error {
 			}
 			return fmt.Errorf("failed to create lockfile %s: %w", lockfilePath, err)
 		}
+	}
 
 	// open a huge mmapped file
 	b.mmapfPath = filepath.Join(b.Dir, "events")
@@ -131,6 +137,7 @@ func (b *MultiMmapManager) Init() error {
 			b.indexId = dbi
 		}
 
+		if !b.ReadOnly {
 			// scan index table to calculate free ranges from used positions
 			b.freeRanges, err = b.gatherFreeRanges(txn)
 			if err != nil {
@@ -144,6 +151,7 @@ func (b *MultiMmapManager) Init() error {
 				}
 			}
 			logOp.Msg("calculated free ranges from index scan")
+		}
 
 		return nil
 	}); err != nil {
@@ -162,7 +170,9 @@ func (b *MultiMmapManager) EnsureLayer(name string) (*IndexingLayer, error) {
 		name: name,
 	}
 
-	err := b.lmdbEnv.Update(func(txn *lmdb.Txn) error {
+	var err error
+	if b.ReadOnly {
+		err = b.lmdbEnv.View(func(txn *lmdb.Txn) error {
 			txn.RawRead = true
 
 			nameb := []byte(name)
@@ -190,6 +200,22 @@ func (b *MultiMmapManager) EnsureLayer(name string) (*IndexingLayer, error) {
 				return err
 			}
 		})
+	} else {
+		err = b.lmdbEnv.Update(func(txn *lmdb.Txn) error {
+			txn.RawRead = true
+
+			nameb := []byte(name)
+			if idv, err := txn.Get(b.knownLayers, nameb); err == nil {
+				if err := il.Init(); err != nil {
+					return fmt.Errorf("failed to init read-only layer %s: %w", name, err)
+				}
+				il.id = binary.BigEndian.Uint16(idv)
+				return nil
+			} else {
+				return err
+			}
+		})
+	}
 	if err != nil {
 		return nil, err
 	}
@@ -199,6 +225,10 @@ func (b *MultiMmapManager) EnsureLayer(name string) (*IndexingLayer, error) {
 }
 
 func (b *MultiMmapManager) DropLayer(name string) error {
+	if b.ReadOnly {
+		return ReadOnly
+	}
+
 	b.writeMutex.Lock()
 	defer b.writeMutex.Unlock()
 

eventstore/mmm/replace.go

@@ -11,6 +11,10 @@ import (
 )
 
 func (il *IndexingLayer) ReplaceEvent(evt nostr.Event) error {
+	if il.mmmm.ReadOnly {
+		return ReadOnly
+	}
+
 	il.mmmm.writeMutex.Lock()
 	defer il.mmmm.writeMutex.Unlock()
 

eventstore/mmm/save.go

@@ -16,6 +16,10 @@ import (
 )
 
 func (il *IndexingLayer) SaveEvent(evt nostr.Event) error {
+	if il.mmmm.ReadOnly {
+		return ReadOnly
+	}
+
 	il.mmmm.writeMutex.Lock()
 	defer il.mmmm.writeMutex.Unlock()