logging: Support zstd roll compression

Author: francislavoie

caddytest/integration/caddyfile_adapt/log_roll_days.caddyfiletest

@@ -6,6 +6,7 @@ log one {
 		dir_mode 0755
 		roll_size 1gb
 		roll_uncompressed
+		roll_compression none
 		roll_local_time
 		roll_keep 5
 		roll_keep_for 90d
@@ -16,6 +17,7 @@ log two {
 		mode 0777
 		dir_mode from_file
 		roll_size 1gib
+		roll_compression zstd
 		roll_interval 12h
 		roll_at 00:00 06:00 12:00,18:00
 		roll_minutes 10 40 45,46
@@ -39,6 +41,7 @@ log two {
 					"filename": "/var/log/access.log",
 					"mode": "0644",
 					"output": "file",
+					"roll_compression": "none",
 					"roll_gzip": false,
 					"roll_keep": 5,
 					"roll_keep_days": 90,
@@ -61,6 +64,7 @@ log two {
 						"12:00",
 						"18:00"
 					],
+					"roll_compression": "zstd",
 					"roll_interval": 43200000000000,
 					"roll_keep": 10,
 					"roll_keep_days": 90,

modules/logging/filewriter.go

@@ -122,9 +122,16 @@ type FileWriter struct {
 	// See https://github.com/DeRuina/timberjack#%EF%B8%8F-rotation-notes--warnings for caveats
 	RollAt []string `json:"roll_at,omitempty"`
 
-	// Whether to compress rolled files. Default: true
+	// Whether to compress rolled files.
+	// Default: true.
+	// Deprecated: Use RollCompression instead, setting it to "none".
 	RollCompress *bool `json:"roll_gzip,omitempty"`
 
+	// RollCompression selects the compression algorithm for rolled files.
+	// Accepted values: "none", "gzip", "zstd".
+	// Default: gzip
+	RollCompression string `json:"roll_compression,omitempty"`
+
 	// Whether to use local timestamps in rolled filenames.
 	// Default: false
 	RollLocalTime bool `json:"roll_local_time,omitempty"`
@@ -254,13 +261,32 @@ func (fw FileWriter) OpenWriter() (io.WriteCloser, error) {
 	if fw.RollKeepDays == 0 {
 		fw.RollKeepDays = 90
 	}
+
+	// Determine compression algorithm to use. Priority:
+	// 1) explicit RollCompression (none|gzip|zstd)
+	// 2) if RollCompress is unset or true -> gzip
+	// 3) if RollCompress is false -> none
+	var compression string
+	if fw.RollCompression != "" {
+		compression = strings.ToLower(strings.TrimSpace(fw.RollCompression))
+		if compression != "none" && compression != "gzip" && compression != "zstd" {
+			return nil, fmt.Errorf("invalid roll_compression: %s", fw.RollCompression)
+		}
+	} else {
+		if fw.RollCompress == nil || *fw.RollCompress {
+			compression = "gzip"
+		} else {
+			compression = "none"
+		}
+	}
+
 	return &timberjack.Logger{
 		Filename:         fw.Filename,
 		MaxSize:          fw.RollSizeMB,
 		MaxAge:           fw.RollKeepDays,
 		MaxBackups:       fw.RollKeep,
 		LocalTime:        fw.RollLocalTime,
-		Compress:         *fw.RollCompress,
+		Compression:      compression,
 		RotationInterval: fw.RollInterval,
 		RotateAtMinutes:  fw.RollAtMinutes,
 		RotateAt:         fw.RollAt,
@@ -332,6 +358,7 @@ func mkdirAllFromFile(dir string, fileMode os.FileMode) error {
 //	    roll_disabled
 //	    roll_size     <size>
 //	    roll_uncompressed
+//	    roll_compression <none|gzip|zstd>
 //	    roll_local_time
 //	    roll_keep     <num>
 //	    roll_keep_for <days>
@@ -413,6 +440,19 @@ func (fw *FileWriter) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 				return d.ArgErr()
 			}
 
+		case "roll_compression":
+			var comp string
+			if !d.AllArgs(&comp) {
+				return d.ArgErr()
+			}
+			comp = strings.ToLower(strings.TrimSpace(comp))
+			switch comp {
+			case "none", "gzip", "zstd":
+				fw.RollCompression = comp
+			default:
+				return d.Errf("parsing roll_compression: must be 'none', 'gzip' or 'zstd'")
+			}
+
 		case "roll_local_time":
 			fw.RollLocalTime = true
 			if d.NextArg() {