glog: add --log_max_size_mb and --log_max_files runtime flags (#8684)

weed/glog/glog_file.go

@@ -33,7 +33,11 @@ import (
 )
 
 // MaxSize is the maximum size of a log file in bytes.
+// It is initialized from the --log_max_size_mb flag when the first log file is created.
 var MaxSize uint64 = 1024 * 1024 * 1800
+
+// MaxFileCount is the maximum number of log files retained per severity level.
+// It is initialized from the --log_max_files flag when the first log file is created.
 var MaxFileCount = 5
 
 // logDirs lists the candidate directories for new log files.
@@ -43,7 +47,25 @@ var logDirs []string
 // See createLogDirs for the full list of possible destinations.
 var logDir = flag.String("logdir", "", "If non-empty, write log files in this directory")
 
+// logMaxSizeMB controls the maximum size of each log file in megabytes.
+// When a log file reaches this size it is closed and a new file is created.
+// Defaults to 1800 MB. Set to 0 to use the compiled-in default.
+var logMaxSizeMB = flag.Uint64("log_max_size_mb", 1800, "Maximum size in megabytes of each log file before it is rotated (0 = use default of 1800 MB)")
+
+// logMaxFiles controls how many log files are kept per severity level.
+// Older files are deleted when the limit is exceeded.
+// Defaults to 5.
+var logMaxFiles = flag.Int("log_max_files", 5, "Maximum number of log files to keep per severity level before older ones are deleted (0 = use default of 5)")
+
 func createLogDirs() {
+	// Apply flag values now that flags have been parsed.
+	if *logMaxSizeMB > 0 {
+		MaxSize = *logMaxSizeMB * 1024 * 1024
+	}
+	if *logMaxFiles > 0 {
+		MaxFileCount = *logMaxFiles
+	}
+
 	if *logDir != "" {
 		logDirs = append(logDirs, *logDir)
 	} else {