Add zerolog boilerplate helpers

Includes 3 cli vars ("loglevel", "logjson", "logfile")
One public function to configure the global zerolog handler based on
those arguments

other/zerolog.go

@@ -0,0 +1,87 @@
+package other
+
+import (
+	"flag"
+	"io"
+	"os"
+	"strings"
+
+	"github.com/rs/zerolog"
+	"github.com/rs/zerolog/log"
+)
+
+var cliFlagLogLevel = "info"
+var cliFlagLogJson = false
+var cliFlagLogFile = ""
+
+func SetupFlags() {
+	flag.StringVar(
+		&cliFlagLogLevel,
+		"loglevel",
+		"info",
+		"Set the logging level. Valid values (case insensitive) are: debug, info, warn, error, fatal",
+	)
+	flag.BoolVar(
+		&cliFlagLogJson,
+		"logjson",
+		false,
+		"Log json objects to stderr instead of nicely formatted ones",
+	)
+	flag.StringVar(
+		&cliFlagLogFile,
+		"logfile",
+		"",
+		"Set the file to write json formatted log messages to",
+	)
+}
+
+func ConfigureLoggingFromCliArgs() {
+	configLevel()
+	configOutputs()
+}
+
+func configLevel() {
+	switch strings.ToLower(*&cliFlagLogLevel) {
+	case "trace":
+		zerolog.SetGlobalLevel(zerolog.TraceLevel)
+	case "debug":
+		zerolog.SetGlobalLevel(zerolog.DebugLevel)
+	case "info":
+		zerolog.SetGlobalLevel(zerolog.InfoLevel)
+	case "warn":
+		zerolog.SetGlobalLevel(zerolog.WarnLevel)
+	case "error":
+		zerolog.SetGlobalLevel(zerolog.ErrorLevel)
+	case "fatal":
+		zerolog.SetGlobalLevel(zerolog.FatalLevel)
+	default:
+		zerolog.SetGlobalLevel(zerolog.InfoLevel)
+	}
+	log.Info().Str("new-level", *flagLogLevel).Msg("New logging level set")
+}
+
+func configOutputs() {
+	extraLogWriters := []io.Writer{}
+	if cliFlagLogFile != "" {
+		file, err := os.OpenFile(cliFlagLogFile, os.O_APPEND|os.O_CREATE, os.ModeAppend)
+		if err != nil {
+			log.Fatal().Err(err).Msg("Failed to open log file")
+		}
+		// NOTE: Technically this leaks a file handle
+		// Shouldn't matter though since the log file should be open until the very end
+		// Sooooo, eh. Don't care about adding an elaborate system to close the file at the very end.
+		// OS will do that anyway
+		extraLogWriters = append(extraLogWriters, file)
+	}
+	if !cliFlagLogJson {
+		console := zerolog.ConsoleWriter{Out: os.Stderr}
+		log.Logger = zerolog.New(zerolog.MultiLevelWriter(append([]io.Writer{console}, extraLogWriters...)...)).
+			With().
+			Timestamp().
+			Logger()
+	} else {
+		log.Logger = zerolog.New(zerolog.MultiLevelWriter(
+			append([]io.Writer{log.Logger}, extraLogWriters...)...,
+		)).With().Timestamp().Logger()
+	}
+}