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package logcap
import (
"cmp"
"context"
"io"
"log/slog"
"os"
"path/filepath"
"slices"
"strings"
"time"
"github.com/fsnotify/fsnotify"
"github.com/johnandersen777/socialweb-computer-kcp/internal/kit/debounce"
"github.com/johnandersen777/socialweb-computer-kcp/internal/kit/fswatch"
"github.com/johnandersen777/socialweb-computer-kcp/internal/kit/opt"
)
const (
DefaultCap = 64 << 20
DefaultEvery = time.Minute
OldSuffix = ".1"
)
func Rotate(path string, capBytes int64) (bool, error) {
if capBytes <= 0 {
return false, nil
}
st, err := os.Stat(path)
if err != nil || !st.Mode().IsRegular() || st.Size() <= capBytes {
return false, nil
}
in, err := os.Open(path)
if err != nil {
return false, err
}
defer in.Close()
if _, err := in.Seek(-capBytes, io.SeekEnd); err != nil {
return false, err
}
out, err := os.OpenFile(path+OldSuffix, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, st.Mode().Perm())
if err != nil {
return false, err
}
_, cerr := io.Copy(out, in)
if err := out.Close(); cerr == nil {
cerr = err
}
if cerr != nil {
return false, cerr
}
return true, os.Truncate(path, 0)
}
type Config struct {
Dirs []string
Files []string
Cap int64
Every time.Duration
Log *slog.Logger
}
func (c Config) paths() []string {
out := append([]string(nil), c.Files...)
for _, d := range c.Dirs {
entries, err := os.ReadDir(d)
if err != nil {
continue
}
for _, e := range entries {
if e.Type().IsRegular() && strings.HasSuffix(e.Name(), ".log") {
out = append(out, filepath.Join(d, e.Name()))
}
}
}
return out
}
func (c Config) Pass() []string {
capBytes := c.Cap
capBytes = cmp.Or(capBytes, DefaultCap)
var rotated []string
for _, p := range c.paths() {
ok, err := Rotate(p, capBytes)
if err != nil && c.Log != nil {
c.Log.Warn("a log file over its cap was not rotated", "file", p, "err", err.Error())
}
if ok {
rotated = append(rotated, p)
}
}
return rotated
}
func (c Config) watched() []string {
dirs := append([]string(nil), c.Dirs...)
for _, f := range c.Files {
if d := filepath.Dir(f); !slices.Contains(dirs, d) {
dirs = append(dirs, d)
}
}
return dirs
}
func (c Config) tracked(path string) bool {
if slices.Contains(c.Files, path) {
return true
}
return strings.HasSuffix(path, ".log") && slices.Contains(c.Dirs, filepath.Dir(path))
}
func (c Config) warn(msg string, args ...any) {
if c.Log != nil {
c.Log.Warn(msg, args...)
}
}
func Keep(ctx context.Context, c Config) {
pass := func() {
if rotated := c.Pass(); len(rotated) > 0 && c.Log != nil {
c.Log.Info("log files over their cap were rotated; each keeps its newest bytes in a .1 copy", "files", rotated)
}
}
pass()
w, err := fswatch.Shared().Subscribe()
if err != nil {
c.warn("log files are not watched; they are capped only at start", "err", err.Error())
return
}
defer w.Close()
for _, d := range c.watched() {
if err := w.Add(d); err != nil {
c.warn("a log directory is not watched", "dir", d, "err", err.Error())
}
}
d := debounce.New(opt.Positive(c.Every, DefaultEvery), pass)
defer d.Stop()
for {
select {
case <-ctx.Done():
return
case ev, ok := <-w.Events():
if !ok {
return
}
if ev.Has(fsnotify.Write|fsnotify.Create) && c.tracked(ev.Name) {
d.Mark()
}
case err, ok := <-w.Errors():
if !ok {
return
}
c.warn("watching the log files", "err", err.Error())
d.Mark()
}
}
}
