1.2.0

server/fileutil.go

@@ -0,0 +1,161 @@
+package main
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sort"
+	"syscall"
+	"time"
+)
+
+func readConfig(path string) (ConfigDocument, RuntimeConfig, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, RuntimeConfig{}, err
+	}
+	doc, err := decodeDocument(data)
+	if err != nil {
+		return nil, RuntimeConfig{}, fmt.Errorf("parse %s: %w", path, err)
+	}
+	normalized, runtime, apiErr := normalizeConfig(doc)
+	if apiErr != nil {
+		return nil, RuntimeConfig{}, apiErr
+	}
+	return normalized, runtime, nil
+}
+
+func marshalIndented(value any) ([]byte, error) {
+	data, err := jsonMarshalIndent(value)
+	if err != nil {
+		return nil, err
+	}
+	return append(data, '\n'), nil
+}
+
+// jsonMarshalIndent is a variable so file-writing failure paths can be tested.
+var jsonMarshalIndent = func(value any) ([]byte, error) {
+	return json.MarshalIndent(value, "", "\t")
+}
+
+func writeConfig(path string, doc ConfigDocument) error {
+	data, err := marshalIndented(doc)
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return err
+	}
+	mode := os.FileMode(0o644)
+	if info, statErr := os.Stat(path); statErr == nil {
+		mode = info.Mode().Perm()
+		backup := fmt.Sprintf("%s.bak-%s", path, time.Now().Format("20060102-150405.000000000"))
+		if err := copyFile(path, backup, mode); err != nil {
+			return fmt.Errorf("backup config: %w", err)
+		}
+		pruneBackups(path, 10)
+	} else if !errors.Is(statErr, os.ErrNotExist) {
+		return statErr
+	}
+	return atomicWrite(path, data, mode, true)
+}
+
+func writeStatsFile(path string, value any) error {
+	data, err := marshalIndented(value)
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return err
+	}
+	return atomicWrite(path, data, 0o644, false)
+}
+
+func atomicWrite(path string, data []byte, mode os.FileMode, allowBusyFallback bool) error {
+	directory := filepath.Dir(path)
+	tmp, err := os.CreateTemp(directory, ".serverstatus-*.tmp")
+	if err != nil {
+		return err
+	}
+	tmpPath := tmp.Name()
+	defer os.Remove(tmpPath)
+
+	if err := tmp.Chmod(mode); err != nil {
+		tmp.Close()
+		return err
+	}
+	if _, err := tmp.Write(data); err != nil {
+		tmp.Close()
+		return err
+	}
+	if err := tmp.Sync(); err != nil {
+		tmp.Close()
+		return err
+	}
+	if err := tmp.Close(); err != nil {
+		return err
+	}
+	if err := os.Rename(tmpPath, path); err == nil {
+		return syncDirectory(directory)
+	} else if !allowBusyFallback || !errors.Is(err, syscall.EBUSY) {
+		return err
+	}
+
+	// Docker cannot rename over a single-file bind mount. The backup above is
+	// already durable, so truncate and sync the mounted inode as a fallback.
+	file, err := os.OpenFile(path, os.O_WRONLY|os.O_TRUNC, mode)
+	if err != nil {
+		return err
+	}
+	if _, err = file.Write(data); err == nil {
+		err = file.Sync()
+	}
+	closeErr := file.Close()
+	if err != nil {
+		return err
+	}
+	return closeErr
+}
+
+func copyFile(source, destination string, mode os.FileMode) error {
+	in, err := os.Open(source)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+	out, err := os.OpenFile(destination, os.O_CREATE|os.O_EXCL|os.O_WRONLY, mode)
+	if err != nil {
+		return err
+	}
+	if _, err = io.Copy(out, in); err == nil {
+		err = out.Sync()
+	}
+	closeErr := out.Close()
+	if err != nil {
+		return err
+	}
+	return closeErr
+}
+
+func pruneBackups(configPath string, keep int) {
+	matches, err := filepath.Glob(configPath + ".bak-*")
+	if err != nil || len(matches) <= keep {
+		return
+	}
+	sort.Strings(matches)
+	for _, path := range matches[:len(matches)-keep] {
+		_ = os.Remove(path)
+	}
+}
+
+func syncDirectory(directory string) error {
+	dir, err := os.Open(directory)
+	if err != nil {
+		return err
+	}
+	defer dir.Close()
+	return dir.Sync()
+}