1 files changed, 152 insertions, 4 deletions

diff --git a/libpod/events/logfile.go b/libpod/events/logfile.go
index 76173cde9..5091f3723 100644
--- a/libpod/events/logfile.go
+++ b/libpod/events/logfile.go
@@ -1,15 +1,24 @@
+//go:build linux
+// +build linux
+
 package events
 
 import (
+	"bufio"
 	"context"
 	"fmt"
+	"io"
+	"io/ioutil"
 	"os"
+	"path"
 	"time"
 
 	"github.com/containers/podman/v4/pkg/util"
 	"github.com/containers/storage/pkg/lockfile"
+	"github.com/nxadm/tail"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
+	"golang.org/x/sys/unix"
 )
 
 // EventLogFile is the structure for event writing to a logfile. It contains the eventer
@@ -27,21 +36,55 @@ func (e EventLogFile) Write(ee Event) error {
 	}
 	lock.Lock()
 	defer lock.Unlock()
-	f, err := os.OpenFile(e.options.LogFilePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0700)
+
+	eventJSONString, err := ee.ToJSONString()
 	if err != nil {
 		return err
 	}
-	defer f.Close()
-	eventJSONString, err := ee.ToJSONString()
+
+	rotated, err := rotateLog(e.options.LogFilePath, eventJSONString, e.options.LogFileMaxSize)
+	if err != nil {
+		return fmt.Errorf("rotating log file: %w", err)
+	}
+
+	if rotated {
+		rEvent := NewEvent(Rotate)
+		rEvent.Type = System
+		rEvent.Name = e.options.LogFilePath
+		rotateJSONString, err := rEvent.ToJSONString()
+		if err != nil {
+			return err
+		}
+		if err := e.writeString(rotateJSONString); err != nil {
+			return err
+		}
+	}
+
+	return e.writeString(eventJSONString)
+}
+
+func (e EventLogFile) writeString(s string) error {
+	f, err := os.OpenFile(e.options.LogFilePath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0700)
 	if err != nil {
 		return err
 	}
-	if _, err := f.WriteString(fmt.Sprintf("%s\n", eventJSONString)); err != nil {
+	if _, err := f.WriteString(s + "\n"); err != nil {
 		return err
 	}
 	return nil
 }
 
+func (e EventLogFile) getTail(options ReadOptions) (*tail.Tail, error) {
+	reopen := true
+	seek := tail.SeekInfo{Offset: 0, Whence: os.SEEK_END}
+	if options.FromStart || !options.Stream {
+		seek.Whence = 0
+		reopen = false
+	}
+	stream := options.Stream
+	return tail.TailFile(e.options.LogFilePath, tail.Config{ReOpen: reopen, Follow: stream, Location: &seek, Logger: tail.DiscardingLogger, Poll: true})
+}
+
 // Reads from the log file
 func (e EventLogFile) Read(ctx context.Context, options ReadOptions) error {
 	defer close(options.EventChannel)
@@ -107,3 +150,108 @@ func (e EventLogFile) Read(ctx context.Context, options ReadOptions) error {
 func (e EventLogFile) String() string {
 	return LogFile.String()
 }
+
+// Rotates the log file if the log file size and content exceeds limit
+func rotateLog(logfile string, content string, limit uint64) (bool, error) {
+	if limit == 0 {
+		return false, nil
+	}
+	file, err := os.Stat(logfile)
+	if err != nil {
+		return false, err
+	}
+	var filesize = uint64(file.Size())
+	var contentsize = uint64(len([]rune(content)))
+	if filesize+contentsize < limit {
+		return false, nil
+	}
+
+	if err := truncate(logfile); err != nil {
+		return false, err
+	}
+	return true, nil
+}
+
+// Truncates the log file and saves 50% of content to new log file
+func truncate(filePath string) error {
+	orig, err := os.Open(filePath)
+	if err != nil {
+		return err
+	}
+	defer orig.Close()
+
+	origFinfo, err := orig.Stat()
+	if err != nil {
+		return err
+	}
+
+	size := origFinfo.Size()
+	threshold := size / 2
+
+	tmp, err := ioutil.TempFile(path.Dir(filePath), "")
+	if err != nil {
+		// Retry in /tmp in case creating a tmp file in the same
+		// directory has failed.
+		tmp, err = ioutil.TempFile("", "")
+		if err != nil {
+			return err
+		}
+	}
+	defer tmp.Close()
+
+	// Jump directly to the threshold, drop the first line and copy the remainder
+	if _, err := orig.Seek(threshold, 0); err != nil {
+		return err
+	}
+	reader := bufio.NewReader(orig)
+	if _, err := reader.ReadString('\n'); err != nil {
+		if !errors.Is(err, io.EOF) {
+			return err
+		}
+	}
+	if _, err := reader.WriteTo(tmp); err != nil {
+		return fmt.Errorf("writing truncated contents: %w", err)
+	}
+
+	if err := renameLog(tmp.Name(), filePath); err != nil {
+		return fmt.Errorf("writing back %s to %s: %w", tmp.Name(), filePath, err)
+	}
+
+	return nil
+}
+
+// Renames from, to
+func renameLog(from, to string) error {
+	err := os.Rename(from, to)
+	if err == nil {
+		return nil
+	}
+
+	if !errors.Is(err, unix.EXDEV) {
+		return err
+	}
+
+	// Files are not on the same partition, so we need to copy them the
+	// hard way.
+	fFrom, err := os.Open(from)
+	if err != nil {
+		return err
+	}
+	defer fFrom.Close()
+
+	fTo, err := os.Create(to)
+	if err != nil {
+		return err
+	}
+	defer fTo.Close()
+
+	if _, err := io.Copy(fTo, fFrom); err != nil {
+		return fmt.Errorf("writing back from temporary file: %w", err)
+	}
+
+	if err := os.Remove(from); err != nil {
+		return fmt.Errorf("removing temporary file: %w", err)
+	}
+
+	return nil
+}