AdGuardHome/internal/aghos/syslog_windows.go

//go:build windows

package aghos

import (
	"strings"

	"github.com/AdguardTeam/golibs/log"
	"golang.org/x/sys/windows"
	"golang.org/x/sys/windows/svc/eventlog"
)

type eventLogWriter struct {
	el *eventlog.Log
}

// Write implements io.Writer interface for eventLogWriter.
func (w *eventLogWriter) Write(b []byte) (int, error) {
	return len(b), w.el.Info(1, string(b))
}

// configureSyslog sets standard log output to event log.
func configureSyslog(serviceName string) (err error) {
	// Note that the eventlog src is the same as the service name, otherwise we
	// will get "the description for event id cannot be found" warning in every
	// log record.

	// Continue if we receive "registry key already exists" or if we get
	// ERROR_ACCESS_DENIED so that we can log without administrative permissions
	// for pre-existing eventlog sources.
	err = eventlog.InstallAsEventCreate(serviceName, eventlog.Info|eventlog.Warning|eventlog.Error)
	if err != nil &&
		!strings.Contains(err.Error(), "registry key already exists") &&
		err != windows.ERROR_ACCESS_DENIED {
		// Don't wrap the error, because it's informative enough as is.
		return err
	}

	el, err := eventlog.Open(serviceName)
	if err != nil {
		// Don't wrap the error, because it's informative enough as is.
		return err
	}

	log.SetOutput(&eventLogWriter{el: el})

	return nil
}