Bring Fatal Log Level to Slog Handler #8235
Description
// - [slog.LevelDebug] is transformed to [log.SeverityDebug]
// - [slog.LevelInfo] is transformed to [log.SeverityInfo]
// - [slog.LevelWarn] is transformed to [log.SeverityWarn]
// - [slog.LevelError] is transformed to [log.SeverityError]
As you already know, slog doesn't expose a level higher than LevelError. But what we can do is to define higher log levels and use them like this:
const LevelFatal = slog.LevelError + 4
logger.Log(ctx, LevelFatal, "critical log message")Which is logged as "ERROR+4" by default in slog handler. Unless you use a custom ReplaceAttr function like this:
func replaceAttr(_ []string, attr slog.Attr) slog.Attr {
if attr.Key != slog.LevelKey || attr.Value.String() != "ERROR+4" {
return attr
}
return slog.Attr{
Key: slog.LevelKey,
Value: slog.StringValue("FATAL"),
}
}
logger := slog.New(slog.NewJSONHandler(os.Stdout, &slog.HandlerOptions{
ReplaceAttr: replaceAttr
}))
logger.Log(ctx, LevelFatal, "critical log message")I've noticed that the otelslog package maps the slog levels to the otel severities, but it still uses the String() value of the slog.Level instead of Severities own String() value.
Is it possible to switch from the following snippet:
into something like this:
severity := log.Severity(r.Level + sevOffset)
record.SetSeverity(severity)
record.SetSeverityText(severity.String())if not, what is the rationale behind this?