Use LOG_LEVEL env value to set logrus log level

LOG_LEVEL can be any of debug, info, warning, error
If bblfsh backend is ran with --debug flag, log level will be 'trace'

Signed-off-by: David Pordomingo <David.Pordomingo.F@gmail.com>

README.md

@@ -30,6 +30,15 @@ If you don't want to run the **web client** using our *Docker* image you can dow
 ./bblfsh-web -bblfsh-addr <bblfsh-server-addr>
 ```
 
+You can also configure the server in debug mode passing `--debug` extra flag, and the logging level with the `LOG_LEVEL` environment value:
+
+```sh
+LOG_LEVEL={debug,info,warning error} ./bblfsh-web -bblfsh-addr <bblfsh-server-addr> --debug
+```
+
+If none are set, its default values will be logging level `info`, and server in `ReleaseMode`.
+
+
 ## Development
 
 See [CONTRIBUTING.md](CONTRIBUTING.md). There is information about the [application architecture](CONTRIBUTING.md#Architecture) and how to [build](CONTRIBUTING.md#Development) from sources.

server/cmd/bblfsh-web/main.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"os"
 	"time"
 
 	"github.com/bblfsh/web/server"
@@ -25,6 +26,13 @@ func flags() (addr, bblfshAddr string, debug, version bool) {
 	return
 }
 
+var logLevels = map[string]logrus.Level{
+	"debug":   logrus.DebugLevel,
+	"info":    logrus.InfoLevel,
+	"warning": logrus.WarnLevel,
+	"error":   logrus.ErrorLevel,
+}
+
 func main() {
 	addr, bblfshAddr, debug, showVersion := flags()
 
@@ -33,6 +41,10 @@ func main() {
 		return
 	}
 
+	if level, ok := logLevels[os.Getenv("LOG_LEVEL")]; ok {
+		logrus.SetLevel(level)
+	}
+
 	if !debug {
 		gin.SetMode(gin.ReleaseMode)
 	}