nfd-worker: dynamic configuration of klog

Make it possible to dynamically (at run-time) alter most of the logging
configuration from the config file.

cmd/nfd-worker/main.go

@@ -20,6 +20,7 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"strings"
 
 	"k8s.io/klog/v2"
 
@@ -112,6 +113,8 @@ func initFlags(flagset *flag.FlagSet) (*worker.Args, *worker.ConfigOverrideArgs)
 	flagset.StringVar(&args.ServerNameOverride, "server-name-override", "",
 		"Hostname expected from server certificate, useful in testing")
 
+	initKlogFlags(flagset, args)
+
 	// Flags overlapping with config file options
 	overrides := &worker.ConfigOverrideArgs{
 		LabelWhiteList: &utils.RegexpVal{},
@@ -132,3 +135,24 @@ func initFlags(flagset *flag.FlagSet) (*worker.Args, *worker.ConfigOverrideArgs)
 
 	return args, overrides
 }
+
+func initKlogFlags(flagset *flag.FlagSet, args *worker.Args) {
+	args.Klog = make(map[string]*utils.KlogFlagVal)
+
+	flags := flag.NewFlagSet("klog flags", flag.ContinueOnError)
+	//flags.SetOutput(ioutil.Discard)
+	klog.InitFlags(flags)
+	flags.VisitAll(func(f *flag.Flag) {
+		name := klogConfigOptName(f.Name)
+		args.Klog[name] = utils.NewKlogFlagVal(f)
+		flagset.Var(args.Klog[name], f.Name, f.Usage)
+	})
+}
+
+func klogConfigOptName(flagName string) string {
+	split := strings.Split(flagName, "_")
+	for i, v := range split[1:] {
+		split[i+1] = strings.Title(v)
+	}
+	return strings.Join(split, "")
+}

cmd/nfd-worker/main_test.go

@@ -59,3 +59,19 @@ func TestParseArgs(t *testing.T) {
 		})
 	})
 }
+
+func TestKlogConfigOptName(t *testing.T) {
+	Convey("When converting names of klog command line flags", t, func() {
+		tcs := map[string]string{
+			"":                    "",
+			"a":                   "a",
+			"an_arg":              "anArg",
+			"arg_with_many_parts": "argWithManyParts",
+		}
+		Convey("resulting config option names should be as expected", func() {
+			for input, expected := range tcs {
+				So(klogConfigOptName(input), ShouldEqual, expected)
+			}
+		})
+	})
+}

deployment/node-feature-discovery/values.yaml

@@ -77,6 +77,21 @@ worker:
     #  noPublish: false
     #  sleepInterval: 60s
     #  sources: [all]
+    #  klog:
+    #    addDirHeader: false
+    #    alsologtostderr: false
+    #    logBacktraceAt:
+    #    logtostderr: true
+    #    skipHeaders: false
+    #    stderrthreshold: 2
+    #    v: 0
+    #    vmodule:
+    ##   NOTE: the following options are not dynamically run-time configurable
+    ##         and require a nfd-worker restart to take effect after being changed
+    #    logDir:
+    #    logFile:
+    #    logFileMaxSize: 1800
+    #    skipLogHeaders: false
     #sources:
     #  cpu:
     #    cpuid:

docs/advanced/worker-commandline-reference.md

@@ -232,6 +232,10 @@ configuration file, instead.
 The following logging-related flags are inherited from the
 [klog](https://pkg.go.dev/k8s.io/klog/v2) package.
 
+Note: The logger setup can also be specified via the `core.klog` configuration
+file options. However, the command line flags take precedence over any
+corresponding config file options specified.
+
 #### -add_dir_header
 
 If true, adds the file directory to the header of the log messages.

docs/advanced/worker-configuration-reference.md

@@ -104,6 +104,109 @@ core:
   noPublish: true
 ```
 
+### core.klog
+
+The following options specify the logger configuration. Most of which can be
+dynamically adjusted at run-time.
+
+Note: The logger options can also be specified via command line flags which
+take precedence over any corresponding config file options.
+
+#### core.klog.addDirHeader
+
+If true, adds the file directory to the header of the log messages.
+
+Default: false
+
+Run-time configurable: yes
+
+#### core.klog.alsologtostderr
+
+Log to standard error as well as files.
+
+Default: false
+
+Run-time configurable: yes
+
+#### core.klog.logBacktraceAt
+
+When logging hits line file:N, emit a stack trace.
+
+Default: *empty*
+
+Run-time configurable: yes
+
+#### core.klog.logDir
+
+If non-empty, write log files in this directory.
+
+Default: *empty*
+
+Run-time configurable: no
+
+#### core.klog.logFile
+
+If non-empty, use this log file.
+
+Default: *empty*
+
+Run-time configurable: no
+
+#### core.klog.logFileMaxSize
+
+Defines the maximum size a log file can grow to. Unit is megabytes. If the
+value is 0, the maximum file size is unlimited.
+
+Default: 1800
+
+Run-time configurable: no
+
+#### core.klog.logtostderr
+
+Log to standard error instead of files
+
+Default: true
+
+Run-time configurable: yes
+
+#### core.klog.skipHeaders
+
+If true, avoid header prefixes in the log messages.
+
+Default: false
+
+Run-time configurable: yes
+
+#### core.klog.skipLogHeaders
+
+If true, avoid headers when opening log files.
+
+Default: false
+
+Run-time configurable: no
+
+#### core.klog.stderrthreshold
+
+Logs at or above this threshold go to stderr (default 2)
+
+Run-time configurable: yes
+
+#### core.klog.v
+
+Number for the log level verbosity.
+
+Default: 0
+
+Run-time configurable: yes
+
+#### core.klog.vmodule
+
+Comma-separated list of `pattern=N` settings for file-filtered logging.
+
+Default: *empty*
+
+Run-time configurable: yes
+
 ## sources
 
 The `sources` section contains feature source specific configuration parameters.

nfd-daemonset-combined.yaml.template

@@ -156,6 +156,21 @@ data:
     #  noPublish: false
     #  sleepInterval: 60s
     #  sources: [all]
+    #  klog:
+    #    addDirHeader: false
+    #    alsologtostderr: false
+    #    logBacktraceAt:
+    #    logtostderr: true
+    #    skipHeaders: false
+    #    stderrthreshold: 2
+    #    v: 0
+    #    vmodule:
+    ##   NOTE: the following options are not dynamically run-time configurable
+    ##         and require a nfd-worker restart to take effect after being changed
+    #    logDir:
+    #    logFile:
+    #    logFileMaxSize: 1800
+    #    skipLogHeaders: false
     #sources:
     #  cpu:
     #    cpuid:

nfd-worker-daemonset.yaml.template

@@ -118,6 +118,21 @@ data:
     #  noPublish: false
     #  sleepInterval: 60s
     #  sources: [all]
+    #  klog:
+    #    addDirHeader: false
+    #    alsologtostderr: false
+    #    logBacktraceAt:
+    #    logtostderr: true
+    #    skipHeaders: false
+    #    stderrthreshold: 2
+    #    v: 0
+    #    vmodule:
+    ##   NOTE: the following options are not dynamically run-time configurable
+    ##         and require a nfd-worker restart to take effect after being changed
+    #    logDir:
+    #    logFile:
+    #    logFileMaxSize: 1800
+    #    skipLogHeaders: false
     #sources:
     #  cpu:
     #    cpuid:

nfd-worker-job.yaml.template

@@ -128,6 +128,21 @@ data:
     #  noPublish: false
     #  sleepInterval: 60s
     #  sources: [all]
+    #  klog:
+    #    addDirHeader: false
+    #    alsologtostderr: false
+    #    logBacktraceAt:
+    #    logtostderr: true
+    #    skipHeaders: false
+    #    stderrthreshold: 2
+    #    v: 0
+    #    vmodule:
+    ##   NOTE: the following options are not dynamically run-time configurable
+    ##         and require a nfd-worker restart to take effect after being changed
+    #    logDir:
+    #    logFile:
+    #    logFileMaxSize: 1800
+    #    skipLogHeaders: false
     #sources:
     #  cpu:
     #    cpuid:

nfd-worker.conf.example

@@ -3,6 +3,21 @@
 #  noPublish: false
 #  sleepInterval: 60s
 #  sources: [all]
+#  klog:
+#    addDirHeader: false
+#    alsologtostderr: false
+#    logBacktraceAt:
+#    logtostderr: true
+#    skipHeaders: false
+#    stderrthreshold: 2
+#    v: 0
+#    vmodule:
+##   NOTE: the following options are not dynamically run-time configurable
+##         and require a nfd-worker restart to take effect after being changed
+#    logDir:
+#    logFile:
+#    logFileMaxSize: 1800
+#    skipLogHeaders: false
 #sources:
 #  cpu:
 #    cpuid:

pkg/nfd-worker/nfd-worker.go

@@ -66,6 +66,7 @@ type NFDConfig struct {
 }
 
 type coreConfig struct {
+	Klog           map[string]string
 	LabelWhiteList utils.RegexpVal
 	NoPublish      bool
 	Sources        []string
@@ -88,6 +89,7 @@ type Args struct {
 	Server             string
 	ServerNameOverride string
 
+	Klog      map[string]*utils.KlogFlagVal
 	Overrides ConfigOverrideArgs
 }
 
@@ -209,6 +211,7 @@ func newDefaultConfig() *NFDConfig {
 			LabelWhiteList: utils.RegexpVal{Regexp: *regexp.MustCompile("")},
 			SleepInterval:  duration{60 * time.Second},
 			Sources:        []string{"all"},
+			Klog:           make(map[string]string),
 		},
 	}
 }
@@ -384,8 +387,26 @@ func (c *coreConfig) sanitize() {
 	}
 }
 
-func (w *nfdWorker) configureCore(c coreConfig) {
-	// Determine enabled feature sourcds
+func (w *nfdWorker) configureCore(c coreConfig) error {
+	// Handle klog
+	for k, a := range w.args.Klog {
+		if !a.IsSetFromCmdline() {
+			v, ok := c.Klog[k]
+			if !ok {
+				v = a.DefValue()
+			}
+			if err := a.SetFromConfig(v); err != nil {
+				return err
+			}
+		}
+	}
+	for k := range c.Klog {
+		if _, ok := w.args.Klog[k]; !ok {
+			klog.Warningf("unknown logger option in config: %q", k)
+		}
+	}
+
+	// Determine enabled feature sources
 	sourceList := map[string]struct{}{}
 	all := false
 	for _, s := range c.Sources {
@@ -416,6 +437,7 @@ func (w *nfdWorker) configureCore(c coreConfig) {
 		}
 		klog.Warningf("skipping unknown source(s) %q specified in core.sources (or --sources)", strings.Join(names, ", "))
 	}
+	return nil
 }
 
 // Parse configuration options
@@ -468,7 +490,9 @@ func (w *nfdWorker) configure(filepath string, overrides string) error {
 
 	w.config = c
 
-	w.configureCore(c.Core)
+	if err := w.configureCore(c.Core); err != nil {
+		return err
+	}
 
 	// (Re-)configure all "real" sources, test sources are not configurable
 	for _, s := range allSources {

pkg/utils/flags.go

@@ -18,6 +18,7 @@ package utils
 
 import (
 	"encoding/json"
+	"flag"
 	"fmt"
 	"regexp"
 	"sort"
@@ -98,3 +99,64 @@ func (a *StringSliceVal) String() string {
 	}
 	return strings.Join(*a, ",")
 }
+
+// KlogFlagVal is a wrapper to allow dynamic control of klog from the config file
+type KlogFlagVal struct {
+	flag             *flag.Flag
+	isSetFromCmdLine bool
+}
+
+// Set implements flag.Value interface
+func (k *KlogFlagVal) Set(value string) error {
+	k.isSetFromCmdLine = true
+	return k.flag.Value.Set(value)
+}
+
+// String implements flag.Value interface
+func (k *KlogFlagVal) String() string {
+	if k.flag == nil {
+		return ""
+	}
+	// Need to handle "log_backtrace_at" in a special way
+	s := k.flag.Value.String()
+	if k.flag.Name == "log_backtrace_at" && s == ":0" {
+		s = ""
+	}
+	return s
+}
+
+// DefValue returns the default value of KlogFlagVal as string
+func (k *KlogFlagVal) DefValue() string {
+	// Need to handle "log_backtrace_at" in a special way
+	d := k.flag.DefValue
+	if k.flag.Name == "log_backtrace_at" && d == ":0" {
+		d = ""
+	}
+	return d
+}
+
+// SetFromConfig sets the value without marking it as set from the cmdline
+func (k *KlogFlagVal) SetFromConfig(value string) error {
+	return k.flag.Value.Set(value)
+}
+
+// IsSetFromCmdline returns true if the value has been set via Set()
+func (k *KlogFlagVal) IsSetFromCmdline() bool { return k.isSetFromCmdLine }
+
+// IsBoolFlag implements flag.boolFlag.IsBoolFlag() for wrapped klog flags.
+func (k *KlogFlagVal) IsBoolFlag() bool {
+	if ba, ok := k.flag.Value.(boolFlag); ok {
+		return ba.IsBoolFlag()
+	}
+	return false
+}
+
+// NewKlogFlagVal wraps a klog flag into KlogFlagVal type
+func NewKlogFlagVal(f *flag.Flag) *KlogFlagVal {
+	return &KlogFlagVal{flag: f}
+}
+
+// boolFlag replicates boolFlag interface internal to the flag package
+type boolFlag interface {
+	IsBoolFlag() bool
+}