Can I set a global logging level in Glog?

Question

In Java, which is the language in which I normally work, a common feature of logging libraries is the ability to set a "global" logging level - eg emit to the log file if the level is WARNING or above, otherwise not, regardless of the module where the logging was done.

I want to do the same in Glog, in conjunction with also only logging to the standard error, not a file.

How?

UPDATE: By the time control passes to my code, the executable has already been started - I'm running as an AWS Lambda function - so I'm not sure I have the option to set the Glog state on the command line. Can I do it with function calls?

---

I'm both new to GoLang and I think I just don't understand the internal logic of Go. Because my mind can't penetrate the Glog docs. So this question may seem naive.

Answer 1

Well, I skimmed the docs and glog is controlled by flags, so they have to be present in order for this to work. In your case, you will have to set them at runtime. You are going to want to set logtostderr=true to log to stderr and set the severity level to one of the possible options:
stderrthreshold=[WARNING|ERROR|INFO|FATAL]

Example:

package main

import (
    "flag"
    "fmt"
    "os"

    "github.com/golang/glog"
)

func usage() {
    flag.PrintDefaults()
    os.Exit(2)
}

func init() {
    flag.Usage = usage
    flag.Set("logtostderr", "true")
    flag.Set("stderrthreshold", "WARNING")
    flag.Set("v", "2")
    // This is wa
    flag.Parse()
}

func main() {
    number_of_lines := 10
    for i := 0; i < number_of_lines; i++ {
        glog.V(2).Infof("LINE: %d", i)
        message := fmt.Sprintf("TEST LINE: %d", i)
        glog.Warning(message)
    }
    glog.Flush()
}

Output:

$ ./stackoverflow.exe
I0615 11:03:47.589969   11776 main.go:30] LINE: 0
W0615 11:03:47.590469   11776 main.go:32] TEST LINE: 0
I0615 11:03:47.590969   11776 main.go:30] LINE: 1
W0615 11:03:47.590969   11776 main.go:32] TEST LINE: 1
I0615 11:03:47.590969   11776 main.go:30] LINE: 2
W0615 11:03:47.590969   11776 main.go:32] TEST LINE: 2
I0615 11:03:47.590969   11776 main.go:30] LINE: 3
W0615 11:03:47.590969   11776 main.go:32] TEST LINE: 3
I0615 11:03:47.590969   11776 main.go:30] LINE: 4
W0615 11:03:47.590969   11776 main.go:32] TEST LINE: 4
I0615 11:03:47.591469   11776 main.go:30] LINE: 5
W0615 11:03:47.591469   11776 main.go:32] TEST LINE: 5
I0615 11:03:47.591469   11776 main.go:30] LINE: 6
W0615 11:03:47.591469   11776 main.go:32] TEST LINE: 6
I0615 11:03:47.591469   11776 main.go:30] LINE: 7
W0615 11:03:47.591469   11776 main.go:32] TEST LINE: 7
I0615 11:03:47.591469   11776 main.go:30] LINE: 8
W0615 11:03:47.591469   11776 main.go:32] TEST LINE: 8
I0615 11:03:47.591469   11776 main.go:30] LINE: 9
W0615 11:03:47.591469   11776 main.go:32] TEST LINE: 9