I want to do some watch when env variable/ config property value is changed
I’ve found viper which should support this scenario but didn't able
to make it work.
I see that the OnConfigChange is called but the value from config
is not taken from the config when it change. The config is loaded successfully
I’ve created a sample to demonstrate the issue.
File cfg.go
go/src/myproj/configuration/cfg.go
package configuration
import (
"fmt"
"os"
"strings"
"github.com/fsnotify/fsnotify"
"github.com/sirupsen/logrus"
"github.com/spf13/viper"
)
const (
varLogLevel = "log"
varPathToConfig = "config.file"
)
type Configuration struct {
v *viper.Viper
}
func New() *Configuration {
c := Configuration{
v: viper.New(),
}
c.v.SetDefault(varPathToConfig, "./config.yaml")
c.v.SetDefault(varLogLevel, "info")
c.v.AutomaticEnv()
c.v.SetConfigFile(c.GetPathToConfig())
err := c.v.ReadInConfig() // Find and read the config file
logrus.WithField("path", c.GetPathToConfig()).Warn("loading config")
// just use the default value(s) if the config file was not found
if _, ok := err.(*os.PathError); ok {
logrus.Warnf("no config file '%s' not found. Using default values", c.GetPathToConfig())
} else if err != nil { // Handle other errors that occurred while reading the config file
panic(fmt.Errorf("fatal error while reading the config file: %s", err))
}
setLogLevel(c.GetLogLevel())
// monitor the changes in the config file
c.v.WatchConfig()
c.v.OnConfigChange(func(e fsnotify.Event) {
logrus.WithField("file", e.Name).Warn("Config file changed")
setLogLevel(c.GetLogLevel())
})
return &c
}
// GetLogLevel returns the log level
func (c *Configuration) GetLogLevel() string {
s := c.v.GetString(varLogLevel)
return s
}
// GetPathToConfig returns the path to the config file
func (c *Configuration) GetPathToConfig() string {
return c.v.GetString(varPathToConfig)
}
func setLogLevel(logLevel string) {
logrus.WithField("level", logLevel).Warn("setting log level")
level, err := logrus.ParseLevel(logLevel)
if err != nil {
logrus.WithField("level", logLevel).Fatalf("failed to start: %s", err.Error())
}
logrus.SetLevel(level)
}
And I create some sample web-application server to make the program running in background (to be able to change the config and see wheatear something is changed )
go/src/myproj
package main
import (
"fmt"
"net/http"
"myproj/configuration"
)
func main() {
cfg := configuration.New()
fmt.Println(cfg)
http.HandleFunc("/", HelloServer)
http.ListenAndServe(":8080", nil)
}
func HelloServer(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Hello, %s!", r.URL.Path[1:])
}
The problem is that the function GetLogLevel() bring the old value and not read the value from config ?
This is the sample of config-file (I've put it sibling to the main.go file under the root project folder
This is the project structure
go/src/myproj
- main.go
- configuration #folder
-- cfg.go
- config.yaml
data:
config.yaml: 'log: debug'
when I change it from info to debug (or other option) I see that the event watch was raised but
it not fetch the new value (like debug). Any idea?
update
when I change the configfile like @Tom suggested I was able to see that the log was change but not the level, it stay on warn
This is the logs , I still see the warn
WARN[0000] loading config path=./config.yaml
WARN[0000] setting log level fields.level=info
&{0xc00012e300}
WARN[0008] Config file changed file=config.yaml
WARN[0008] setting log level fields.level=error
WARN[0020] Config file changed file=config.yaml
WARN[0020] setting log level fields.level=debug
WARN[0060] Config file changed file=config.yaml
WARN[0060] setting log level fields.level=warn
