feat: keep reserved space for backup on device (natefinch#206)

README.md

@@ -67,6 +67,10 @@ type Logger struct {
     // deleted.)
     MaxBackups int `json:"maxbackups" yaml:"maxbackups"`
 
+    // ReservedSize is the minimum left space in megabytes of the store device.
+    // Do not to check the available space of the device.
+    ReservedSize int `json:"reservedsize" yaml:"reservedsize"`
+
     // LocalTime determines if the time used for formatting the timestamps in
     // backup files is the computer's local time.  The default is to use UTC
     // time.
@@ -107,8 +111,9 @@ number equal to MaxBackups (or all of them if MaxBackups is 0).  Any files
 with an encoded timestamp older than MaxAge days are deleted, regardless of
 MaxBackups.  Note that the time encoded in the timestamp is the rotation
 time, which may differ from the last time that file was written to.
+The older files will be deleted until there's enough ReservedSize space left.
 
-If MaxBackups and MaxAge are both 0, no old log files will be deleted.
+If MaxBackups and MaxAge and ReservedSize are all 0, no old log files will be deleted.
 
 
 

lumberjack.go

@@ -3,7 +3,7 @@
 // Note that this is v2.0 of lumberjack, and should be imported using gopkg.in
 // thusly:
 //
-//   import "gopkg.in/natefinch/lumberjack.v2"
+//	import "gopkg.in/natefinch/lumberjack.v2"
 //
 // The package name remains simply lumberjack, and the code resides at
 // https://github.com/natefinch/lumberjack under the v2.0 branch.
@@ -32,6 +32,7 @@ import (
 	"sort"
 	"strings"
 	"sync"
+	"syscall"
 	"time"
 )
 
@@ -66,16 +67,18 @@ var _ io.WriteCloser = (*Logger)(nil)
 // `/var/log/foo/server.log`, a backup created at 6:30pm on Nov 11 2016 would
 // use the filename `/var/log/foo/server-2016-11-04T18-30-00.000.log`
 //
-// Cleaning Up Old Log Files
+// # Cleaning Up Old Log Files
 //
 // Whenever a new logfile gets created, old log files may be deleted.  The most
 // recent files according to the encoded timestamp will be retained, up to a
 // number equal to MaxBackups (or all of them if MaxBackups is 0).  Any files
 // with an encoded timestamp older than MaxAge days are deleted, regardless of
 // MaxBackups.  Note that the time encoded in the timestamp is the rotation
 // time, which may differ from the last time that file was written to.
+// The older files will be deleted until there's enough ReservedSize space left.
 //
 // If MaxBackups and MaxAge are both 0, no old log files will be deleted.
+// If MaxBackups and MaxAge and ReservedSize are all 0, no old log files will be deleted.
 type Logger struct {
 	// Filename is the file to write logs to.  Backup log files will be retained
 	// in the same directory.  It uses <processname>-lumberjack.log in
@@ -98,6 +101,10 @@ type Logger struct {
 	// deleted.)
 	MaxBackups int `json:"maxbackups" yaml:"maxbackups"`
 
+	// ReservedSize is the minimum left space in megabytes of the store device.
+	// Do not to check the available space of the device.
+	ReservedSize int `json:"reservedsize" yaml:"reservedsize"`
+
 	// LocalTime determines if the time used for formatting the timestamps in
 	// backup files is the computer's local time.  The default is to use UTC
 	// time.
@@ -300,9 +307,9 @@ func (l *Logger) filename() string {
 // millRunOnce performs compression and removal of stale log files.
 // Log files are compressed if enabled via configuration and old log
 // files are removed, keeping at most l.MaxBackups files, as long as
-// none of them are older than MaxAge.
+// none of them are older than MaxAge, or keep reserved space in device.
 func (l *Logger) millRunOnce() error {
-	if l.MaxBackups == 0 && l.MaxAge == 0 && !l.Compress {
+	if l.MaxBackups == 0 && l.MaxAge == 0 && l.ReservedSize == 0 && !l.Compress {
 		return nil
 	}
 
@@ -347,6 +354,28 @@ func (l *Logger) millRunOnce() error {
 		}
 		files = remaining
 	}
+	if reserved := l.ReservedSize * megabyte; reserved > 0 && len(files) > 0 {
+		var fs syscall.Statfs_t
+		errStat := syscall.Statfs(l.Filename, &fs)
+		if errStat != nil {
+			if err == nil {
+				err = errStat
+			}
+		} else {
+			avail := int(fs.Bavail) * int(fs.Bsize)
+			var remaining []logInfo
+			for idx := len(files) - 1; idx >= 0; idx-- {
+				f := files[idx]
+				if avail < reserved {
+					avail += int(f.Size())
+					remove = append(remove, f)
+				} else {
+					remaining = append(remaining, f)
+				}
+			}
+			files = remaining
+		}
+	}
 
 	if l.Compress {
 		for _, f := range files {

lumberjack_test.go

@@ -587,6 +587,30 @@ func TestRotate(t *testing.T) {
 	existsWithContent(filename, b2, t)
 }
 
+func TestReservedSize(t *testing.T) {
+	currentTime = fakeTime
+	megabyte = 1 << 20
+	dir := makeTempDir("TestReservedSize", t)
+	defer os.RemoveAll(dir)
+
+	l := &Logger{
+		Filename:     logFile(dir),
+		ReservedSize: 1 << 30, // large enough reserved size
+		LocalTime:    true,
+	}
+	defer l.Close()
+	b := []byte("boo!")
+	n, err := l.Write(b)
+	isNil(err, t)
+	equals(len(b), n, t)
+
+	err = l.Rotate()
+	isNil(err, t)
+
+	<-time.After(20 * time.Millisecond)
+	notExist(backupFileLocal(dir), t)
+}
+
 func TestCompressOnRotate(t *testing.T) {
 	currentTime = fakeTime
 	megabyte = 1