genericr
A generic logr implementation that makes it easy to write your own logging backend.
This package allows you to implement the logr interface by implementing a single callback function instead of the full interface.
Examples
Basic example
Basic example that directly writes to stderr:
log := genericr.New(func(e genericr.Entry) {
fmt.Fprintln(os.Stderr, e.String())
})
log.WithName("some-component").WithValues("x", 123).V(1).Info("some event", "y", 42)This outputs the default string representation which currently looks like this:
[1] some-component "some event" x=123 y=42
The genericr.Entry struct you receive in your handler contains the following fields
that you can use to do your own formatting:
type Entry struct {
Level int // level at which this was logged
Name string // name parts joined with '.'
NameParts []string // individual name segments
Message string // message as send to log call
Error error // error if .Error() was called
Fields []interface{} // alternating key-value pairs
// Caller information
Caller runtime.Frame // only available after .WithCaller(true)
CallerDepth int // caller depth from callback
}Use e.FieldsMap() to retrieve the Fields as a map.
To enable caller information, use genericr.New(...).WithCaller(true).
To filter messages above a certain verbosity level, use genericr.New(...).WithVerbosity(1).
Usage in tests
This shows how you can redirect logs to the testing.T logger and keep a reference to the last log entry if you want to check that one:
func TestLogger_Table(t *testing.T) {
var last genericr.Entry
log := genericr.New(func(e genericr.Entry) {
last = e
t.Log(e.String())
})
// ...
}Logrus example
More complicated example that implements a logrus adapter:
root := logrus.New()
root.SetLevel(logrus.TraceLevel)
root.SetFormatter(&logrus.TextFormatter{
DisableColors: true,
DisableTimestamp: true,
})
root.Out = os.Stdout
var lf genericr.LogFunc = func(e genericr.Entry) {
var l *logrus.Entry = root.WithField("component", e.Name)
if e.Error != nil {
l = l.WithError(e.Error)
}
if len(e.Fields) != 0 {
l = l.WithFields(e.FieldsMap())
}
logrusLevel := logrus.Level(e.Level) + logrus.InfoLevel // 0 = info
if logrusLevel < logrus.ErrorLevel {
logrusLevel = logrus.ErrorLevel
} else if logrusLevel > logrus.TraceLevel {
logrusLevel = logrus.TraceLevel
}
l.Log(logrusLevel, e.Message)
}
log := genericr.New(lf)