How to change glog log level at runtime, not compile time?

Question

I'm using the github.com/golang/glog, and want to change the flag stderrthreshold or V-leveled logging at runtime, that is without re-compile the binary and re-run it. I had searched some resource, but all the answers are changes at compile time. Is there anyway to change it at runtime cause I don't want to stop my service?

I think I do the right tagging. https://github.com/golang/glog — hsiaoairplane, Apr 17 '18 at 02:24
you can provide `stderrthreshold` and `--v` by flag, if that what you are asking! — Abdullah Al Maruf - Tuhin, Apr 17 '18 at 04:47

score 2 · Answer 1 · answered Feb 23 '19 at 18:16

glog package reads configuration from flags. You can modify the flags at runtime from your code to change glog's behaviour.

package main

import (
    "flag"
    "fmt"

    "github.com/golang/glog"
)

func main() {
    // glog needs flag.Parse() call
    flag.Parse()
    glog.Info("default level")
    glog.V(3).Info("Level 3 log")
    if glog.V(3) {
        fmt.Println("Changing log level to 5")
        flag.Lookup("v").Value.Set("5")
    }
    glog.V(4).Info("Level 4 log")

    glog.V(5).Info("Level 5 log")

}

Results in

➜ ./main --alsologtostderr -v 2
I0223 23:42:26.661984    4587 main.go:12] default level
➜ ./main --alsologtostderr -v 3
I0223 23:42:28.209673    4600 main.go:12] default level
I0223 23:42:28.210174    4600 main.go:13] Level 3 log
Changing log level to 5
I0223 23:42:28.210210    4600 main.go:18] Level 4 log
I0223 23:42:28.210230    4600 main.go:20] Level 5 log
➜ ./main --alsologtostderr -v 4
I0223 23:42:30.927222    4614 main.go:12] default level
I0223 23:42:30.928018    4614 main.go:13] Level 3 log
Changing log level to 5
I0223 23:42:30.928072    4614 main.go:18] Level 4 log
I0223 23:42:30.928088    4614 main.go:20] Level 5 log

How to change glog log level at runtime, not compile time?

1 Answers1