feat: extract meta.db from 2.x Bolt file (#27031)

A small utility to extract the V1 metadata from 
a V2 bolt database for debugging use.

Author: davidby-influx

cmd/extract-meta/main.go

@@ -0,0 +1,113 @@
+// extract-meta extracts the v1_tsm1_metadata value from an InfluxDB BoltDB file
+// and writes it to a file in binary format, or optionally as JSON.
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"os"
+
+	"github.com/influxdata/influxdb/v2/v1/services/meta"
+	bolt "go.etcd.io/bbolt"
+)
+
+func main() {
+	var (
+		boltPath   string
+		outputPath string
+		asJSON     bool
+	)
+
+	flag.StringVar(&boltPath, "bolt", "", "path to the BoltDB file (e.g., influxd.bolt)")
+	flag.StringVar(&outputPath, "out", "", "output file path; use - for stdout (default: stdout for JSON, meta.db.bin for binary)")
+	flag.BoolVar(&asJSON, "json", false, "output as JSON instead of binary")
+	flag.Parse()
+
+	if boltPath == "" {
+		fmt.Fprintln(os.Stderr, "error: -bolt flag is required")
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	if err := run(boltPath, outputPath, asJSON); err != nil {
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
+	}
+}
+
+func run(boltPath, outputPath string, asJSON bool) error {
+	db, err := bolt.Open(boltPath, 0600, &bolt.Options{ReadOnly: true})
+	if err != nil {
+		return fmt.Errorf("failed to open bolt db %s: %w", boltPath, err)
+	}
+	defer db.Close()
+
+	var data []byte
+
+	err = db.View(func(tx *bolt.Tx) error {
+		bucket := tx.Bucket(meta.BucketName)
+		if bucket == nil {
+			return fmt.Errorf("bucket %q not found", string(meta.BucketName))
+		}
+
+		val := bucket.Get([]byte(meta.Filename))
+		if val == nil {
+			return fmt.Errorf("key %q not found in bucket %q", meta.Filename, string(meta.BucketName))
+		}
+
+		// Copy the value since it's only valid for the duration of the transaction
+		data = make([]byte, len(val))
+		copy(data, val)
+
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+
+	if asJSON {
+		// Unmarshal the protobuf data
+		var metaData meta.Data
+		if err := metaData.UnmarshalBinary(data); err != nil {
+			return fmt.Errorf("failed to unmarshal metadata: %w", err)
+		}
+
+		// Marshal to JSON
+		jsonData, err := json.MarshalIndent(&metaData, "", "  ")
+		if err != nil {
+			return fmt.Errorf("failed to marshal to JSON: %w", err)
+		}
+
+		if outputPath == "" || outputPath == "-" {
+			// Write to stdout
+			if _, err = os.Stdout.Write(jsonData); err != nil {
+				return fmt.Errorf("failed to write JSON to stdout: %w", err)
+			}
+		} else {
+			if err := os.WriteFile(outputPath, jsonData, 0644); err != nil {
+				return fmt.Errorf("failed to write output file %s: %w", outputPath, err)
+			}
+			fmt.Fprintf(os.Stderr, "wrote JSON to %s\n", outputPath)
+		}
+	} else {
+		// Binary output
+		if outputPath == "-" {
+			// Write to stdout
+			if _, err := os.Stdout.Write(data); err != nil {
+				return fmt.Errorf("failed to write binary to stdout: %w", err)
+			}
+		} else {
+			if outputPath == "" {
+				outputPath = "meta.db.bin"
+			}
+			if err := os.WriteFile(outputPath, data, 0644); err != nil {
+				return fmt.Errorf("failed to write output file %s: %w", outputPath, err)
+			}
+			fmt.Printf("extracted %d bytes from %s[%s][%s] to %s\n",
+				len(data), boltPath, string(meta.BucketName), meta.Filename, outputPath)
+		}
+	}
+
+	return nil
+}