fix: order command controls after dispatch

2026-09-11 08:56:00 +00:00
parent f6f900e597
commit 684981c235
13 changed files with 360 additions and 38 deletions
@@ -0,0 +1,156 @@
+package observability
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strconv"
+	"sync"
+	"time"
+)
+
+// RotatingFile is an append-only daemon log with bounded numbered archives.
+// It is deliberately a single-process writer: deployment supplies one daemon
+// process per configured path, and a second writer must use a distinct file.
+// Archive .1 is newest; .maxFiles is oldest.
+type RotatingFile struct {
+	mu       sync.Mutex
+	path     string
+	maxBytes uint64
+	maxFiles uint32
+	file     *os.File
+	size     uint64
+}
+
+// OpenRotatingFile opens path for append, creating its parent directories with
+// conservative permissions. A blank path disables file logging and returns a
+// no-op closer. Both rotation controls must be zero (unbounded) or positive.
+func OpenRotatingFile(path string, maxBytes uint64, maxFiles uint32) (io.WriteCloser, error) {
+	if path == "" {
+		return nopWriteCloser{Writer: io.Discard}, nil
+	}
+	if (maxBytes == 0) != (maxFiles == 0) {
+		return nil, errors.New("log rotation byte/file limits must both be zero or positive")
+	}
+	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
+		return nil, fmt.Errorf("create log directory: %w", err)
+	}
+	result := &RotatingFile{path: path, maxBytes: maxBytes, maxFiles: maxFiles}
+	if err := result.open(); err != nil {
+		return nil, err
+	}
+	return result, nil
+}
+
+func (file *RotatingFile) open() error {
+	opened, err := os.OpenFile(file.path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0o600)
+	if err != nil {
+		return fmt.Errorf("open log file: %w", err)
+	}
+	info, err := opened.Stat()
+	if err != nil {
+		_ = opened.Close()
+		return fmt.Errorf("stat log file: %w", err)
+	}
+	file.file = opened
+	file.size = uint64(info.Size())
+	return nil
+}
+
+func (file *RotatingFile) Write(data []byte) (int, error) {
+	file.mu.Lock()
+	defer file.mu.Unlock()
+	if file.file == nil {
+		return 0, os.ErrClosed
+	}
+	if file.maxBytes != 0 && file.size != 0 && (file.size >= file.maxBytes || uint64(len(data)) > file.maxBytes-file.size) {
+		if err := file.rotate(); err != nil {
+			return 0, err
+		}
+	}
+	written, err := file.file.Write(data)
+	file.size += uint64(written)
+	return written, err
+}
+
+func (file *RotatingFile) Close() error {
+	file.mu.Lock()
+	defer file.mu.Unlock()
+	if file.file == nil {
+		return nil
+	}
+	err := file.file.Close()
+	file.file = nil
+	return err
+}
+
+func (file *RotatingFile) rotate() error {
+	if err := file.file.Close(); err != nil {
+		return fmt.Errorf("close log before rotation: %w", err)
+	}
+	file.file = nil
+	oldest := file.archivePath(file.maxFiles)
+	if err := os.Remove(oldest); err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("remove oldest log archive: %w", err)
+	}
+	for index := file.maxFiles; index > 1; index-- {
+		from := file.archivePath(index - 1)
+		to := file.archivePath(index)
+		if err := os.Rename(from, to); err != nil && !errors.Is(err, os.ErrNotExist) {
+			return fmt.Errorf("rotate log archive: %w", err)
+		}
+	}
+	if err := os.Rename(file.path, file.archivePath(1)); err != nil && !errors.Is(err, os.ErrNotExist) {
+		return fmt.Errorf("seal current log: %w", err)
+	}
+	return file.open()
+}
+
+func (file *RotatingFile) archivePath(index uint32) string {
+	return file.path + "." + strconv.FormatUint(uint64(index), 10)
+}
+
+type nopWriteCloser struct{ io.Writer }
+
+func (nopWriteCloser) Close() error { return nil }
+
+// FormatLog makes file records either newline-delimited JSON or plain text.
+// It is intentionally applied only to daemon diagnostics, never command
+// output, stdin, environment values, or other payload-bearing data.
+func FormatLog(destination io.Writer, format string) io.Writer {
+	if destination == nil || format != "json" {
+		return destination
+	}
+	return &jsonLogWriter{destination: destination}
+}
+
+type jsonLogWriter struct {
+	mu          sync.Mutex
+	destination io.Writer
+}
+
+func (writer *jsonLogWriter) Write(data []byte) (int, error) {
+	writer.mu.Lock()
+	defer writer.mu.Unlock()
+	for _, line := range bytes.Split(data, []byte{'\n'}) {
+		if len(line) == 0 {
+			continue
+		}
+		record, err := json.Marshal(struct {
+			Time    string `json:"time"`
+			Level   string `json:"level"`
+			Message string `json:"message"`
+		}{Time: time.Now().UTC().Format(time.RFC3339Nano), Level: "info", Message: string(line)})
+		if err != nil {
+			return 0, fmt.Errorf("encode structured log: %w", err)
+		}
+		if _, err := writer.destination.Write(append(record, '\n')); err != nil {
+			return 0, err
+		}
+	}
+	return len(data), nil
+}