Support SIGUSR1 log level incrementing (sensu#3685)

This commit adds support to sensu-backend and sensu-agent for
incrementing the log level with SIGUSR1. When the process receives
this signal, the log level will be incremented in terms of
verbosity. When the level is at TRACE, the most verbose log level,
and the log level is incremented, it will wrap around to error
level.

Known issues: SIGUSR1 is not supported on Windows.

Signed-off-by: Eric Chlebek <[email protected]>

CHANGELOG.md

@@ -13,6 +13,8 @@ Versioning](http://semver.org/spec/v2.0.0.html).
 - [Web] Added the ability for labels and annotations with links to images to be
 displayed inline.
 - [Web] Added additional modes for those with colour blindness.
+- Users can now increment the logging level by sending SIGUSR1 to the
+sensu-backend or sensu-agent process.
 - Added a new `sensuctl describe-type` command to list all resource types.
 
 ### Changed

agent/cmd/logger.go

@@ -1,6 +1,8 @@
 package cmd
 
-import "github.com/sirupsen/logrus"
+import (
+	"github.com/sirupsen/logrus"
+)
 
 var logger = logrus.WithFields(logrus.Fields{
 	"component": "cmd",

agent/cmd/logger_unix.go

@@ -0,0 +1,30 @@
+// +build !windows
+
+package cmd
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/sensu/sensu-go/util/logging"
+	"github.com/sirupsen/logrus"
+)
+
+func init() {
+	sigs := make(chan os.Signal, 1)
+	signal.Notify(sigs, syscall.SIGUSR1)
+	go func() {
+		for range sigs {
+			level := logrus.GetLevel()
+			newLevel := logging.IncrementLogLevel(level)
+			logrus.Warnf("set log level to %s", newLevel)
+			logrus.SetLevel(newLevel)
+			if newLevel == logrus.WarnLevel {
+				// repeat the log call, as it wouldn't have been logged at
+				// error level.
+				logrus.Warnf("set log level to %s", newLevel)
+			}
+		}
+	}()
+}

backend/cmd/logger.go

@@ -1,6 +1,8 @@
 package cmd
 
-import "github.com/sirupsen/logrus"
+import (
+	"github.com/sirupsen/logrus"
+)
 
 var logger = logrus.WithFields(logrus.Fields{
 	"component": "cmd",

backend/cmd/logger_unix.go

@@ -0,0 +1,30 @@
+// +build !windows
+
+package cmd
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/sensu/sensu-go/util/logging"
+	"github.com/sirupsen/logrus"
+)
+
+func init() {
+	sigs := make(chan os.Signal, 1)
+	signal.Notify(sigs, syscall.SIGUSR1)
+	go func() {
+		for range sigs {
+			level := logrus.GetLevel()
+			newLevel := logging.IncrementLogLevel(level)
+			logrus.Warnf("set log level to %s", newLevel)
+			logrus.SetLevel(newLevel)
+			if newLevel == logrus.WarnLevel {
+				// repeat the log call, as it wouldn't have been logged at
+				// error level.
+				logrus.Warnf("set log level to %s", newLevel)
+			}
+		}
+	}()
+}

util/logging/logging.go

@@ -46,3 +46,13 @@ func EventFields(event *types.Event, debug bool) map[string]interface{} {
 
 	return fields
 }
+
+// IncrementLogLevel increments the log level, or wraps around to "error" level.
+func IncrementLogLevel(level logrus.Level) logrus.Level {
+	level++
+	if level > logrus.TraceLevel {
+		// wrap around to error level
+		level = logrus.ErrorLevel
+	}
+	return level
+}

util/logging/logging_test.go

@@ -0,0 +1,42 @@
+package logging
+
+import (
+	"testing"
+
+	"github.com/sirupsen/logrus"
+)
+
+func TestIncrementLogLevel(t *testing.T) {
+	tests := []struct {
+		Level    logrus.Level
+		ExpLevel logrus.Level
+	}{
+		{
+			Level:    logrus.ErrorLevel,
+			ExpLevel: logrus.WarnLevel,
+		},
+		{
+			Level:    logrus.WarnLevel,
+			ExpLevel: logrus.InfoLevel,
+		},
+		{
+			Level:    logrus.InfoLevel,
+			ExpLevel: logrus.DebugLevel,
+		},
+		{
+			Level:    logrus.DebugLevel,
+			ExpLevel: logrus.TraceLevel,
+		},
+		{
+			Level:    logrus.TraceLevel,
+			ExpLevel: logrus.ErrorLevel,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.Level.String(), func(t *testing.T) {
+			if got, want := IncrementLogLevel(test.Level), test.ExpLevel; got != want {
+				t.Fatalf("bad log level: got %s, want %s", got, want)
+			}
+		})
+	}
+}