Add logfile_max_archives feature and test.

logger/log.go

@@ -18,6 +18,9 @@ import (
 	"fmt"
 	"log"
 	"os"
+	"path/filepath"
+	"sort"
+	"strings"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -128,13 +131,14 @@ type fileLogger struct {
 	out       int64
 	canRotate int32
 	sync.Mutex
-	l      *Logger
-	f      writerAndCloser
-	limit  int64
-	olimit int64
-	pid    string
-	time   bool
-	closed bool
+	l            *Logger
+	f            writerAndCloser
+	limit        int64
+	olimit       int64
+	pid          string
+	time         bool
+	closed       bool
+	archiveLimit int
 }
 
 func newFileLogger(filename, pidPrefix string, time bool) (*fileLogger, error) {
@@ -169,6 +173,12 @@ func (l *fileLogger) setLimit(limit int64) {
 	}
 }
 
+func (l *fileLogger) setArchiveLimit(limit int) {
+	l.Lock()
+	l.archiveLimit = limit
+	l.Unlock()
+}
+
 func (l *fileLogger) logDirect(label, format string, v ...interface{}) int {
 	var entrya = [256]byte{}
 	var entry = entrya[:0]
@@ -190,6 +200,46 @@ func (l *fileLogger) logDirect(label, format string, v ...interface{}) int {
 	return len(entry)
 }
 
+func (l *fileLogger) archivePurge(fname string) {
+	// Evaluate number of saved backups for purge
+	// l readlock held
+	var backups []string
+	lDir := filepath.Dir(fname)
+	lBase := filepath.Base(fname)
+	entries, err := os.ReadDir(lDir)
+	if err != nil {
+		l.logDirect(l.l.errorLabel, "Unable to read directory %q for log purge (%v), will attempt next rotation", lDir, err)
+		return
+	}
+	for _, entry := range entries {
+		if entry.IsDir() || entry.Name() == lBase || !strings.HasPrefix(entry.Name(), lBase) {
+			continue
+		}
+		stamp, found := strings.CutPrefix(entry.Name(), fmt.Sprintf("%s%s", lBase, "."))
+		if found {
+			_, err := time.Parse("2006:01:02:15:04:05.999999999", strings.Replace(stamp, ".", ":", 5))
+			if err == nil {
+				backups = append(backups, entry.Name())
+			}
+		}
+	}
+	archives := len(backups)
+	if archives > l.archiveLimit {
+		// Oldest to latest
+		sort.Slice(backups, func(i, j int) bool {
+			return backups[i] < backups[j]
+		})
+		for i := 0; i < archives-l.archiveLimit; i++ {
+			if err := os.Remove(fmt.Sprintf("%s%s%s", lDir, string(os.PathSeparator), backups[i])); err != nil {
+				l.logDirect(l.l.errorLabel, "Unable to remove backup log file %q (%v), will attempt next rotation", backups[i], err)
+				// Bail fast, we'll try again next rotation
+				return
+			}
+			l.logDirect(l.l.infoLabel, "Removed archived log file %q", backups[i])
+		}
+	}
+}
+
 func (l *fileLogger) Write(b []byte) (int, error) {
 	if atomic.LoadInt32(&l.canRotate) == 0 {
 		n, err := l.f.Write(b)
@@ -225,6 +275,9 @@ func (l *fileLogger) Write(b []byte) (int, error) {
 			n := l.logDirect(l.l.infoLabel, "Rotated log, backup saved as %q", bak)
 			l.out = int64(n)
 			l.limit = l.olimit
+			if l.archiveLimit > 0 {
+				l.archivePurge(fname)
+			}
 		}
 	}
 	l.Unlock()
@@ -257,6 +310,19 @@ func (l *Logger) SetSizeLimit(limit int64) error {
 	return nil
 }
 
+// SetArchiveLimit sets the number of archived log files that will be retained
+func (l *Logger) SetArchiveLimit(limit int) error {
+	l.Lock()
+	if l.fl == nil {
+		l.Unlock()
+		return fmt.Errorf("can set log archive limit only for file logger")
+	}
+	fl := l.fl
+	l.Unlock()
+	fl.setArchiveLimit(limit)
+	return nil
+}
+
 // NewTestLogger creates a logger with output directed to Stderr with a prefix.
 // Useful for tracing in tests when multiple servers are in the same pid
 func NewTestLogger(prefix string, time bool) *Logger {

server/log.go

@@ -72,6 +72,16 @@ func (s *Server) ConfigureLogger() {
 				l.SetSizeLimit(opts.LogSizeLimit)
 			}
 		}
+		if opts.LogMaxArchives > 0 {
+			if l, ok := log.(*srvlog.Logger); ok {
+				al := int(opts.LogMaxArchives)
+				if int64(al) != opts.LogMaxArchives {
+					// set to default (no max) on overflow
+					al = 0
+				}
+				l.SetArchiveLimit(al)
+			}
+		}
 	} else if opts.RemoteSyslog != "" {
 		log = srvlog.NewRemoteSysLogger(opts.RemoteSyslog, opts.Debug, opts.Trace)
 	} else if syslog {

server/opts.go

@@ -311,6 +311,7 @@ type Options struct {
 	PortsFileDir          string            `json:"-"`
 	LogFile               string            `json:"-"`
 	LogSizeLimit          int64             `json:"-"`
+	LogMaxArchives        int64             `json:"-"`
 	Syslog                bool              `json:"-"`
 	RemoteSyslog          string            `json:"-"`
 	Routes                []*url.URL        `json:"-"`
@@ -999,6 +1000,8 @@ func (o *Options) processConfigFileLine(k string, v interface{}, errors *[]error
 		o.LogFile = v.(string)
 	case "logfile_size_limit", "log_size_limit":
 		o.LogSizeLimit = v.(int64)
+	case "logfile_max_archives", "log_max_archives":
+		o.LogMaxArchives = v.(int64)
 	case "syslog":
 		o.Syslog = v.(bool)
 		trackExplicitVal(o, &o.inConfig, "Syslog", o.Syslog)

test/log_test.go

@@ -0,0 +1,129 @@
+package test
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats-server/v2/server"
+)
+
+func RunServerWithLogging(opts *server.Options) *server.Server {
+	if opts == nil {
+		opts = &DefaultTestOptions
+	}
+	opts.NoLog = false
+	opts.Cluster.PoolSize = -1
+	opts.Cluster.Compression.Mode = server.CompressionOff
+	opts.LeafNode.Compression.Mode = server.CompressionOff
+	s, err := server.NewServer(opts)
+	if err != nil || s == nil {
+		panic(fmt.Sprintf("No NATS Server object returned: %v", err))
+	}
+	s.ConfigureLogger()
+	go s.Start()
+	if !s.ReadyForConnections(10 * time.Second) {
+		panic("Unable to start NATS Server in Go Routine")
+	}
+	return s
+}
+
+func TestLogMaxArchives(t *testing.T) {
+	// With logfile_size_limit set to small 100 characters, plain startup rotates 8 times
+	for _, test := range []struct {
+		name               string
+		config             string
+		totEntriesExpected int
+	}{
+		{
+			"Default implicit, no max archives, expect 0 purged archives",
+			`
+				port: -1
+				log_file: %s
+				logfile_size_limit: 100
+			`,
+			9,
+		},
+		{
+			"Default explicit, no max archives, expect 0 purged archives",
+			`
+				port: -1
+				log_file: %s
+				logfile_size_limit: 100
+				logfile_max_archives: 0
+			`,
+			9,
+		},
+		{
+			"Default explicit - negative val, no max archives, expect 0 purged archives",
+			`
+				port: -1
+				log_file: %s
+				logfile_size_limit: 100
+				logfile_max_archives: -42
+			`,
+			9,
+		},
+		{
+			"1-archive limit, expect 7 purged archives",
+			`
+				port: -1
+				log_file: %s
+				logfile_size_limit: 100
+				logfile_max_archives: 1
+			`,
+			2,
+		},
+		{
+			"5-archive limit, expect 4 purged archives",
+			`
+				port: -1
+				log_file: %s
+				logfile_size_limit: 100
+				logfile_max_archives: 5
+			`,
+			6,
+		},
+		{
+			"100-archive limit, expect 0 purged archives",
+			`
+				port: -1
+				log_file: %s
+				logfile_size_limit: 100
+				logfile_max_archives: 100
+			`,
+			9,
+		},
+	} {
+		t.Run(test.name, func(t *testing.T) {
+			d, err := os.MkdirTemp("", "logtest")
+			if err != nil {
+				t.Fatalf("Error creating temp dir: %v", err)
+			}
+			content := fmt.Sprintf(test.config, filepath.Join(d, "nats-server.log"))
+			// server config does not like plain windows backslash
+			if runtime.GOOS == "windows" {
+				content = filepath.ToSlash(content)
+			}
+			opts, err := server.ProcessConfigFile(createConfFile(t, []byte(content)))
+			if err != nil {
+				t.Fatalf("Error processing config file: %v", err)
+			}
+			s := RunServerWithLogging(opts)
+			if s == nil {
+				t.Fatalf("No NATS Server object returned")
+			}
+			s.Shutdown()
+			entries, err := os.ReadDir(d)
+			if err != nil {
+				t.Fatalf("Error reading dir: %v", err)
+			}
+			if len(entries) != test.totEntriesExpected {
+				t.Fatalf("Expected %d log files, got %d", test.totEntriesExpected, len(entries))
+			}
+		})
+	}
+}