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add more error reporting and fallback mode for docker

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This commit is contained in:
Leo Antunes 2018-08-23 00:25:12 +02:00
parent 092698694f
commit 42552f4316
3 changed files with 38 additions and 9 deletions
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1
docker.go
View file

@ -132,6 +132,7 @@ func waitForConnection(client dockerClienter) {
log.Info("retrying connection to docker")
_, err := client.Ping(context.Background())
if err != nil {
log.Errorf("error pinging docker server: %s", err)
return fmt.Errorf("error pinging docker server: %s", err)
}
return nil

44
etchosts.go
View file

@ -17,8 +17,9 @@ const (
)
func writeToEtcHosts(ipsToNames ipsToNamesMap) error {
// this will fail if the file doesn't exist, which is probably ok
etcHosts, err := os.Open(config.EtcHostsPath)
// We do not want to create the hosts file; if it's not there, we probably have the wrong path.
// Open RW because we might have to write to it (see movePreservePerms)
etcHosts, err := os.OpenFile(config.EtcHostsPath, os.O_RDWR, 0644)
if err != nil {
return fmt.Errorf("could not open %s for reading: %s", config.EtcHostsPath, err)
}
@ -55,7 +56,10 @@ func writeToEtcHosts(ipsToNames ipsToNamesMap) error {
}
ip := tokens[0]
if names, ok := ipsToNames[ip]; ok {
writeEntryWithBanner(tmp, ip, names)
err = writeEntryWithBanner(tmp, ip, names)
if err != nil {
return err
}
delete(ipsToNames, ip) // otherwise we'll append it again below
}
} else {
@ -63,10 +67,16 @@ func writeToEtcHosts(ipsToNames ipsToNamesMap) error {
fmt.Fprintf(tmp, "%s\n", line)
}
}
if err := scanner.Err(); err != nil {
return fmt.Errorf("error reading %s: %s", config.EtcHostsPath, err)
}
// append remaining entries to file
for ip, names := range ipsToNames {
writeEntryWithBanner(tmp, ip, names)
err = writeEntryWithBanner(tmp, ip, names)
if err != nil {
return err
}
}
err = movePreservePerms(tmp, etcHosts)
@ -77,12 +87,17 @@ func writeToEtcHosts(ipsToNames ipsToNamesMap) error {
return nil
}
func writeEntryWithBanner(tmp io.Writer, ip string, names []string) {
func writeEntryWithBanner(tmp io.Writer, ip string, names []string) error {
if len(names) > 0 {
log.Debugf("writing entry for %s (%s)", ip, names)
fmt.Fprintf(tmp, "%s\n", banner)
fmt.Fprintf(tmp, "%s\t%s\n", ip, strings.Join(names, " "))
if _, err := fmt.Fprintf(tmp, "%s\n", banner); err != nil {
return fmt.Errorf("error writing entry for %s: %s", ip, err)
}
if _, err := fmt.Fprintf(tmp, "%s\t%s\n", ip, strings.Join(names, " ")); err != nil {
return fmt.Errorf("error writing entry for %s: %s", ip, err)
}
}
return nil
}
func movePreservePerms(src, dst *os.File) error {
@ -93,7 +108,20 @@ func movePreservePerms(src, dst *os.File) error {
err = os.Rename(src.Name(), dst.Name())
if err != nil {
return fmt.Errorf("could not rename to %s: %s", config.EtcHostsPath, err)
log.Infof("could not rename to %s; falling back to less safe direct-write (%s)", config.EtcHostsPath, err)
if _, err := src.Seek(0, io.SeekStart); err != nil {
return err
}
if _, err := dst.Seek(0, io.SeekStart); err != nil {
return err
}
if err := dst.Truncate(0); err != nil {
return err
}
_, err = io.Copy(dst, src)
return err
}
// ensure we're not running with some umask that might break things

2
main.go
View file

@ -65,7 +65,7 @@ func main() {
client, err := docker.NewEnvClient()
if err != nil {
log.Fatalf("error starting docker client: %s", err)
log.Fatalf("error initializing docker client: %s", err)
}
defer client.Close()