added the ability to discover backend nodes via srv records

.gitignore

@@ -1 +1,2 @@
 bin/
+remco

backends/consul/config.go

@@ -11,6 +11,7 @@ package consul
 import (
 	"github.com/HeavyHorst/easyKV/consul"
 	berr "github.com/HeavyHorst/remco/backends/error"
+	"github.com/HeavyHorst/remco/backends/srvRecord"
 	"github.com/HeavyHorst/remco/log"
 	"github.com/HeavyHorst/remco/template"
 	"github.com/Sirupsen/logrus"
@@ -20,9 +21,10 @@ import (
 type Config struct {
 	Nodes        []string
 	Scheme       string
-	ClientCert   string `toml:"client_cert"`
-	ClientKey    string `toml:"client_key"`
-	ClientCaKeys string `toml:"client_ca_keys"`
+	SRVRecord    srvRecord.Record `toml:"srv_record"`
+	ClientCert   string           `toml:"client_cert"`
+	ClientKey    string           `toml:"client_key"`
+	ClientCaKeys string           `toml:"client_ca_keys"`
 	template.Backend
 }
 
@@ -32,6 +34,16 @@ func (c *Config) Connect() (template.Backend, error) {
 		return template.Backend{}, berr.ErrNilConfig
 	}
 	c.Backend.Name = "consul"
+
+	// No nodes are set but a SRVRecord is provided
+	if len(c.Nodes) == 0 && c.SRVRecord != "" {
+		var err error
+		c.Nodes, err = c.SRVRecord.GetNodesFromSRV("")
+		if err != nil {
+			return c.Backend, err
+		}
+	}
+
 	log.WithFields(logrus.Fields{
 		"backend": c.Backend.Name,
 		"nodes":   c.Nodes,

backends/etcd/config.go

@@ -11,6 +11,7 @@ package etcd
 import (
 	"github.com/HeavyHorst/easyKV/etcd"
 	berr "github.com/HeavyHorst/remco/backends/error"
+	"github.com/HeavyHorst/remco/backends/srvRecord"
 	"github.com/HeavyHorst/remco/log"
 	"github.com/HeavyHorst/remco/template"
 	"github.com/Sirupsen/logrus"
@@ -19,9 +20,11 @@ import (
 // Config represents the config for the etcd backend.
 type Config struct {
 	Nodes        []string
-	ClientCert   string `toml:"client_cert"`
-	ClientKey    string `toml:"client_key"`
-	ClientCaKeys string `toml:"client_ca_keys"`
+	Scheme       string           //only needed for etcdv2 with SRVRecord
+	ClientCert   string           `toml:"client_cert"`
+	ClientKey    string           `toml:"client_key"`
+	ClientCaKeys string           `toml:"client_ca_keys"`
+	SRVRecord    srvRecord.Record `toml:"srv_record"`
 	Username     string
 	Password     string
 	Version      int
@@ -45,6 +48,24 @@ func (c *Config) Connect() (template.Backend, error) {
 		c.Backend.Name = "etcd"
 	}
 
+	// No nodes are set but a SRVRecord is provided
+	if len(c.Nodes) == 0 && c.SRVRecord != "" {
+		var err error
+		if c.Version != 2 {
+			// no scheme required for etcdv3
+			c.Scheme = ""
+		} else if c.Scheme == "" {
+			// etcd version is 2 and no scheme is provided
+			// use http as default value
+			c.Scheme = "http"
+		}
+		c.Nodes, err = c.SRVRecord.GetNodesFromSRV(c.Scheme)
+
+		if err != nil {
+			return c.Backend, err
+		}
+	}
+
 	log.WithFields(logrus.Fields{
 		"backend": c.Backend.Name,
 		"nodes":   c.Nodes,

backends/redis/config.go

@@ -11,16 +11,18 @@ package redis
 import (
 	"github.com/HeavyHorst/easyKV/redis"
 	berr "github.com/HeavyHorst/remco/backends/error"
+	"github.com/HeavyHorst/remco/backends/srvRecord"
 	"github.com/HeavyHorst/remco/log"
 	"github.com/HeavyHorst/remco/template"
 	"github.com/Sirupsen/logrus"
 )
 
 // Config represents the config for the redis backend.
 type Config struct {
-	Nodes    []string
-	Password string
-	Database int
+	Nodes     []string
+	SRVRecord srvRecord.Record `toml:"srv_record"`
+	Password  string
+	Database  int
 	template.Backend
 }
 
@@ -31,6 +33,16 @@ func (c *Config) Connect() (template.Backend, error) {
 	}
 
 	c.Backend.Name = "redis"
+
+	// No nodes are set but a SRVRecord is provided
+	if len(c.Nodes) == 0 && c.SRVRecord != "" {
+		var err error
+		c.Nodes, err = c.SRVRecord.GetNodesFromSRV("")
+		if err != nil {
+			return c.Backend, err
+		}
+	}
+
 	log.WithFields(logrus.Fields{
 		"backend": c.Backend.Name,
 		"nodes":   c.Nodes,

backends/srvRecord/srvRecord.go

@@ -0,0 +1,40 @@
+/*
+ * This file is part of remco.
+ * © 2016 The Remco Authors
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+package srvRecord
+
+import (
+	"fmt"
+	"net"
+	"strings"
+)
+
+// Record is a SRV-Record string
+// for example _etcd-client._tcp.example.com.
+type Record string
+
+// GetNodesFromSRV returns the nodes stored in the record
+func (r Record) GetNodesFromSRV(scheme string) ([]string, error) {
+	var nodes []string
+	_, addrs, err := net.LookupSRV("", "", string(r))
+	if err != nil {
+		return nodes, err
+	}
+
+	for _, srv := range addrs {
+		port := fmt.Sprintf("%d", srv.Port)
+		host := strings.TrimRight(srv.Target, ".")
+		host = net.JoinHostPort(host, port)
+		if scheme != "" {
+			host = fmt.Sprintf("%s://%s", scheme, host)
+		}
+
+		nodes = append(nodes, host)
+	}
+	return nodes, nil
+}

backends/zookeeper/config.go

@@ -11,14 +11,16 @@ package zookeeper
 import (
 	"github.com/HeavyHorst/easyKV/zookeeper"
 	berr "github.com/HeavyHorst/remco/backends/error"
+	"github.com/HeavyHorst/remco/backends/srvRecord"
 	"github.com/HeavyHorst/remco/log"
 	"github.com/HeavyHorst/remco/template"
 	"github.com/Sirupsen/logrus"
 )
 
 // Config represents the config for the consul backend.
 type Config struct {
-	Nodes []string
+	Nodes     []string
+	SRVRecord srvRecord.Record `toml:"srv_record"`
 	template.Backend
 }
 
@@ -29,6 +31,16 @@ func (c *Config) Connect() (template.Backend, error) {
 	}
 
 	c.Backend.Name = "zookeeper"
+
+	// No nodes are set but a SRVRecord is provided
+	if len(c.Nodes) == 0 && c.SRVRecord != "" {
+		var err error
+		c.Nodes, err = c.SRVRecord.GetNodesFromSRV("")
+		if err != nil {
+			return c.Backend, err
+		}
+	}
+
 	log.WithFields(logrus.Fields{
 		"backend": c.Backend.Name,
 		"nodes":   c.Nodes,

docs/content/config/configuration-options.md

@@ -58,23 +58,27 @@ weight: 10
 <details>
 <summary> **valid in every backend** </summary>
 
+ - **keys([]string):**
+   - The backend keys that the template requires to be rendered correctly. The child keys are also loaded.
  - **watch(bool, optional):**
    - Enable watch support. Default is false.
- - **prefix(string):**
+ - **prefix(string, optional):**
    - Key path prefix. Default is "".
- - **interval(int):**
+ - **interval(int, optional):**
    - The backend polling interval. Can be used as a reconcilation loop for watch or standalone.
  - **onetime(bool, optional):**
    - Render the config file and quit. Default is false.
- - **keys([]string):**
-   - The backend keys that the template requires to be rendered correctly. The child keys are also loaded.
 </details>
 
 <details>
 <summary> **etcd** </summary>
 
  - **nodes([]string):**
    - List of backend nodes.
+ - **srv_record(string, optional):**
+   - A DNS server record to discover the etcd nodes.
+ - **scheme(string, optional):**
+   - The backend URI scheme (http or https). This is only used when the nodes are discovered via DNS srv records and the api level is 2. Default is http.
  - **client_cert(string, optional):**
    - The client cert file.
  - **client_key(string, optional):**
@@ -93,9 +97,11 @@ weight: 10
 <summary> **consul** </summary>
 
  - **nodes([]string):**
-    - List of backend nodes.
+   - List of backend nodes.
+ - **srv_record(string, optional):**
+   - A DNS server record to discover the consul nodes.
  - **scheme(string):**
-    - the backend URI scheme (http or https).
+   - The backend URI scheme (http or https).
  - **client_cert(string, optional):**
    - The client cert file.
  - **client_key(string, optional):**
@@ -116,6 +122,8 @@ weight: 10
 
  - **nodes([]string):**
    - List of backend nodes.
+ - **srv_record(string), optional:**
+   - A DNS server record to discover the redis nodes.
  - **password(string, optional):**
    - The redis password.
  - **database(int, optional):**
@@ -126,7 +134,7 @@ weight: 10
 <summary> **vault** </summary>
 
  - **node(string):**
-    - The backend node.
+   - The backend node.
  - **auth_type(string):**
    - The vault authentication type. (token, approle, app-id, userpass, github)
  - **auth_token(string):**
@@ -161,4 +169,6 @@ weight: 10
 
  - **nodes([]string):**
    - List of backend nodes.
+ - **srv_record(string, optional):**
+   - A DNS server record to discover the zookeeper nodes.
 </details>