init.go, main.go: don't use logs.ConfigureLogging

This function is somewhat strange and I always wanted to remove it,
as it tries to satisfy both init.go and main.go, which have somewhat
different needs.

It is more straightforward and readable to configure logrus directly.

While at it, simplify errors on panic (errors from logrus.ParseLevel
and strconv.Atoi already contain value which they fail to parse, and
panic already contains enough context to figure out what's wrong).

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

init.go

@@ -1,13 +1,11 @@
 package main
 
 import (
-	"fmt"
 	"os"
 	"runtime"
 	"strconv"
 
 	"github.com/opencontainers/runc/libcontainer"
-	"github.com/opencontainers/runc/libcontainer/logs"
 	_ "github.com/opencontainers/runc/libcontainer/nsenter"
 	"github.com/sirupsen/logrus"
 )
@@ -19,25 +17,19 @@ func init() {
 		runtime.GOMAXPROCS(1)
 		runtime.LockOSThread()
 
-		level := os.Getenv("_LIBCONTAINER_LOGLEVEL")
-		logLevel, err := logrus.ParseLevel(level)
+		logLevel, err := logrus.ParseLevel(os.Getenv("_LIBCONTAINER_LOGLEVEL"))
 		if err != nil {
-			panic(fmt.Sprintf("libcontainer: failed to parse log level: %q: %v", level, err))
+			panic(err)
 		}
 
-		logPipeFdStr := os.Getenv("_LIBCONTAINER_LOGPIPE")
-		logPipeFd, err := strconv.Atoi(logPipeFdStr)
+		logPipeFd, err := strconv.Atoi(os.Getenv("_LIBCONTAINER_LOGPIPE"))
 		if err != nil {
-			panic(fmt.Sprintf("libcontainer: failed to convert environment variable _LIBCONTAINER_LOGPIPE=%s to int: %s", logPipeFdStr, err))
-		}
-		err = logs.ConfigureLogging(logs.Config{
-			LogPipeFd: logPipeFd,
-			LogFormat: "json",
-			LogLevel:  logLevel,
-		})
-		if err != nil {
-			panic(fmt.Sprintf("libcontainer: failed to configure logging: %v", err))
+			panic(err)
 		}
+
+		logrus.SetLevel(logLevel)
+		logrus.SetOutput(os.NewFile(uintptr(logPipeFd), "logpipe"))
+		logrus.SetFormatter(new(logrus.JSONFormatter))
 		logrus.Debug("child process in init()")
 
 		factory, _ := libcontainer.New("")