prometheus/util/osutil/hostname.go

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// Copyright 2021 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package osutil
import (
"encoding"
"net"
"os"
)
// GetFQDN returns a FQDN if it's possible, otherwise falls back to hostname.
func GetFQDN() (string, error) {
hostname, err := os.Hostname()
if err != nil {
return "", err
}
ips, err := net.LookupIP(hostname)
if err != nil {
// Return the system hostname if we can't look up the IP address.
return hostname, nil
}
lookup := func(ipStr encoding.TextMarshaler) (string, error) {
ip, err := ipStr.MarshalText()
if err != nil {
return "", err
}
hosts, err := net.LookupAddr(string(ip))
if err != nil || len(hosts) == 0 {
return "", err
}
return hosts[0], nil
}
for _, addr := range ips {
if ip := addr.To4(); ip != nil {
if fqdn, err := lookup(ip); err == nil {
return fqdn, nil
}
}
if ip := addr.To16(); ip != nil {
if fqdn, err := lookup(ip); err == nil {
return fqdn, nil
}
}
}
return hostname, nil
}