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package main
import (
const consul_addr string = "KV2S3_CONSUL_ADDR"
const enc_key string = "KV2S3_ENC_KEY"
const key_exp_bits int = 256
const key_exp_bytes int = key_exp_bits / 8
func errIsPanic(err error, format string, a ...interface{}) {
if err != nil {
log.Panicf(format, a...)
func absentIsErr(present bool) error {
if !present {
return errors.New("Environement variable is not set.")
return nil
func main() {
log.Println("starting consul kv backup...")
//--- Ask Consul to Snapshot our KV
var present bool
conf := api.DefaultConfig()
conf.Address, present = os.LookupEnv(consul_addr)
err := absentIsErr(present)
errIsPanic(err, "%v env required. %v", consul_addr, err)
//@FIXME add later support for HTTPS
options := api.QueryOptions {
// Prevent from backuping forever silently a desynchronized node
AllowStale: false,
consul, err := api.NewClient(conf)
errIsPanic(err, "Unable to build a new client. %v", err)
reader, _, err := consul.Snapshot().Save(&options)
defer reader.Close()
errIsPanic(err, "Snapshot failed. %v", err)
//--- Get encryption key and check it
b64_key, present := os.LookupEnv(enc_key)
err = absentIsErr(present)
errIsPanic(err, "%v env required. %v", enc_key, err)
raw_key, err := base64.StdEncoding.DecodeString(b64_key)
errIsPanic(err, "Unable to decode base64 key. %v", err)
err = nil
key_size_bytes := len(raw_key)
key_size_bits := key_size_bytes
if key_size_bytes != key_exp_bytes {
msg := fmt.Sprintf(
"Key size is %d bits (%d bytes) instead of %d bits (%d bytes).",
err = errors.New(msg)
errIsPanic(err, "We deliberately support only 256 bits (32 bytes) keys. %v", err)
//--- Encryption
// Not a simple thing to do it in a streaming manner - is it only a good idea?