Introduce trace logging in Control Plane components

[siggy]

What problem are you trying to solve?

In the Go-based Control Plane components, the debug log level is quite verbose. This is the highest log level available in the Control Plane:

linkerd2/pkg/flags/flags.go

Lines 36 to 37 in d0e837d

	logLevel := cmd.String("log-level", log.InfoLevel.String(),
	"log level, must be one of: panic, fatal, error, warn, info, debug")

Also, the debug log level sets klog to v=12, potentially exposing sensitive authorization tokens:

linkerd2/pkg/flags/flags.go

Line 72 in d0e837d

flag.Set("v", "12") // At 7 and higher, authorization tokens get logged.

How should the problem be solved?

Introduce a trace log level. Change debug to klog v=6, set trace at v=12:

diff --git a/pkg/flags/flags.go b/pkg/flags/flags.go
index 8ce0c67f8..7df09f25d 100644
--- a/pkg/flags/flags.go
+++ b/pkg/flags/flags.go
@@ -34,7 +34,7 @@ func ConfigureAndParse(cmd *flag.FlagSet, args []string) {
        flag.Set("log_file", "/dev/null")
        flag.Set("v", "0")
        logLevel := cmd.String("log-level", log.InfoLevel.String(),
-               "log level, must be one of: panic, fatal, error, warn, info, debug")
+               "log level, must be one of: panic, fatal, error, warn, info, debug, trace")
        logFormat := cmd.String("log-format", "plain",
                "log format, must be one of: plain, json")
        printVersion := cmd.Bool("version", false, "print version and exit")
@@ -66,13 +66,17 @@ func setLogLevel(logLevel string) {
        }
        log.SetLevel(level)

-       if level == log.DebugLevel {
+       if level >= log.DebugLevel {
                flag.Set("stderrthreshold", "INFO")
                flag.Set("logtostderr", "true")
-               flag.Set("v", "12") // At 7 and higher, authorization tokens get logged.
+               flag.Set("v", "6")
                // pipe klog entries to logrus
                klog.SetOutput(log.StandardLogger().Writer())
        }
+
+       if level >= log.TraceLevel {
+               flag.Set("v", "12") // At 7 and higher, authorization tokens get logged.
+       }
 }

 func maybePrintVersionAndExit(printVersion bool) {

Any alternatives you've considered?

Don't use debug logs.

How would users interact with this feature?

Via helm and CLI flags.

Would you like to work on this feature?

maybe