feat(constraints): Supports kv stores backends

docs/toml.md

@@ -64,6 +64,55 @@
 # defaultEntryPoints = ["http", "https"]
 ```
 
+### Constraints
+
+In a micro-service architecture, with a central service discovery, setting constraints limits Træfɪk scope to a smaller number of routes.
+
+Træfɪk filters services according to service attributes/tags set in your configuration backends.
+
+Supported backends:
+
+- Docker
+- Consul K/V
+- BoltDB
+- Zookeeper
+- Etcd
+- Consul Catalog
+
+Supported filters:
+
+- ```tag```
+
+```
+# Constraints definition
+
+#
+# Optional
+#
+
+# Simple matching constraint
+# constraints = ["tag==api"]
+
+# Simple mismatching constraint
+# constraints = ["tag!=api"]
+
+# Globbing
+# constraints = ["tag==us-*"]
+
+# Backend-specific constraint
+# [consulCatalog]
+#   endpoint = 127.0.0.1:8500
+#   constraints = ["tag==api"]
+
+# Multiple constraints
+#   - "tag==" must match with at least one tag
+#   - "tag!=" must match with none of tags
+# constraints = ["tag!=us-*", "tag!=asia-*"]
+# [consulCatalog]
+#   endpoint = 127.0.0.1:8500
+#   constraints = ["tag==api", "tag!=v*-beta"]
+```
+
 ## Entrypoints definition
 
 ```toml
@@ -834,6 +883,13 @@ prefix = "traefik"
 # cert = "/etc/ssl/consul.crt"
 # key = "/etc/ssl/consul.key"
 # insecureskipverify = true
+
+# Constraint on ConsulKV tags
+#
+# Optional
+#
+# constraints = ["tag==api", "tag==he*ld"]
+# Matching with containers having a key "/traefik/backends/backend1/servers/server1/tags" equal to "api,helloworld"
 ```
 
 Please refer to the [Key Value storage structure](/user-guide/kv-config/#key-value-storage-structure) section to get documentation on traefik KV structure.
@@ -937,6 +993,13 @@ prefix = "/traefik"
 # cert = "/etc/ssl/etcd.crt"
 # key = "/etc/ssl/etcd.key"
 # insecureskipverify = true
+
+# Constraint on Etcd tags
+#
+# Optional
+#
+# constraints = ["tag==api", "tag==he*ld"]
+# Matching with containers having a key "/traefik/backends/backend1/servers/server1/tags" equal to "api,helloworld"
 ```
 
 Please refer to the [Key Value storage structure](/user-guide/kv-config/#key-value-storage-structure) section to get documentation on traefik KV structure.
@@ -980,6 +1043,13 @@ prefix = "/traefik"
 # Optional
 #
 # filename = "zookeeper.tmpl"
+
+# Constraint on Zookeeper tags
+#
+# Optional
+#
+# constraints = ["tag==api", "tag==he*ld"]
+# Matching with containers having a key "/traefik/backends/backend1/servers/server1/tags" equal to "api,helloworld"
 ```
 
 Please refer to the [Key Value storage structure](/user-guide/kv-config/#key-value-storage-structure) section to get documentation on traefik KV structure.
@@ -1022,6 +1092,13 @@ prefix = "/traefik"
 # Optional
 #
 # filename = "boltdb.tmpl"
+
+# Constraint on BoltDB tags
+#
+# Optional
+#
+# constraints = ["tag==api", "tag==he*ld"]
+# Matching with containers having a key "/traefik/backends/backend1/servers/server1/tags" equal to "api,helloworld"
 ```
 
 Please refer to the [Key Value storage structure](/user-guide/kv-config/#key-value-storage-structure) section to get documentation on traefik KV structure.

docs/user-guide/kv-config.md

@@ -225,6 +225,7 @@ And there, the same dynamic configuration in a KV Store (using `prefix = "traefi
 | `/traefik/backends/backend1/servers/server1/weight`    | `10`                        |
 | `/traefik/backends/backend1/servers/server2/url`       | `http://172.17.0.3:80`      |
 | `/traefik/backends/backend1/servers/server2/weight`    | `1`                         |
+| `/traefik/backends/backend1/servers/server2/tags`      | `api,helloworld`            |
 
 - backend 2
 
@@ -237,6 +238,7 @@ And there, the same dynamic configuration in a KV Store (using `prefix = "traefi
 | `/traefik/backends/backend2/servers/server1/weight` | `1`                    |
 | `/traefik/backends/backend2/servers/server2/url`    | `http://172.17.0.5:80` |
 | `/traefik/backends/backend2/servers/server2/weight` | `2`                    |
+| `/traefik/backends/backend2/servers/server2/tags`   | `web`                  |
 
 - frontend 1
 

provider/kv.go

@@ -83,6 +83,38 @@ func (provider *Kv) watchKv(configurationChan chan<- types.ConfigMessage, prefix
 }
 
 func (provider *Kv) provide(configurationChan chan<- types.ConfigMessage, pool *safe.Pool, constraints []types.Constraint) error {
+	provider.Constraints = append(provider.Constraints, constraints...)
+	storeConfig := &store.Config{
+		ConnectionTimeout: 30 * time.Second,
+		Bucket:            "traefik",
+	}
+
+	if provider.TLS != nil {
+		caPool := x509.NewCertPool()
+
+		if provider.TLS.CA != "" {
+			ca, err := ioutil.ReadFile(provider.TLS.CA)
+
+			if err != nil {
+				return fmt.Errorf("Failed to read CA. %s", err)
+			}
+
+			caPool.AppendCertsFromPEM(ca)
+		}
+
+		cert, err := tls.LoadX509KeyPair(provider.TLS.Cert, provider.TLS.Key)
+
+		if err != nil {
+			return fmt.Errorf("Failed to load TLS keypair: %v", err)
+		}
+
+		storeConfig.TLS = &tls.Config{
+			Certificates:       []tls.Certificate{cert},
+			RootCAs:            caPool,
+			InsecureSkipVerify: provider.TLS.InsecureSkipVerify,
+		}
+	}
+
 	operation := func() error {
 		if _, err := provider.kvclient.Exists("qmslkjdfmqlskdjfmqlksjazçueznbvbwzlkajzebvkwjdcqmlsfj"); err != nil {
 			return fmt.Errorf("Failed to test KV store connection: %v", err)
@@ -119,17 +151,26 @@ func (provider *Kv) loadConfig() *types.Configuration {
 		// Allow `/traefik/alias` to superesede `provider.Prefix`
 		strings.TrimSuffix(provider.get(provider.Prefix, provider.Prefix+"/alias"), "/"),
 	}
+
 	var KvFuncMap = template.FuncMap{
-		"List":     provider.list,
+		"List":             provider.list,
-		"Get":      provider.get,
+		"Get":              provider.get,
-		"SplitGet": provider.splitGet,
+		"SplitGet":         provider.splitGet,
-		"Last":     provider.last,
+		"Last":             provider.last,
+		"CheckConstraints": provider.checkConstraints,
 	}
 
 	configuration, err := provider.getConfiguration("templates/kv.tmpl", KvFuncMap, templateObjects)
 	if err != nil {
 		log.Error(err)
 	}
+
+	for key, frontend := range configuration.Frontends {
+		if _, ok := configuration.Backends[frontend.Backend]; ok == false {
+			delete(configuration.Frontends, key)
+		}
+	}
+
 	return configuration
 }
 
@@ -178,3 +219,23 @@ func (provider *Kv) last(key string) string {
 	splittedKey := strings.Split(key, "/")
 	return splittedKey[len(splittedKey)-1]
 }
+
+func (provider *Kv) checkConstraints(keys ...string) string {
+	joinedKeys := strings.Join(keys, "")
+	keyPair, err := provider.kvclient.Get(joinedKeys)
+
+	value := ""
+	if err == nil && keyPair != nil && keyPair.Value != nil {
+		value = string(keyPair.Value)
+	}
+
+	constraintTags := strings.Split(value, ",")
+	ok, failingConstraint := provider.MatchConstraints(constraintTags)
+	if ok == false {
+		if failingConstraint != nil {
+			log.Debugf("Constraint %v not matching with following tags: %v", failingConstraint.String(), value)
+		}
+		return "false"
+	}
+	return "true"
+}

templates/kv.tmpl

@@ -28,11 +28,13 @@
 {{end}}
 
 {{range $servers}}
+{{if ne (CheckConstraints "" . "/tags") "false"}}
 [backends."{{Last $backend}}".servers."{{Last .}}"]
     url = "{{Get "" . "/url"}}"
     weight = {{Get ""  . "/weight"}}
 {{end}}
 {{end}}
+{{end}}
 
 [frontends]{{range $frontends}}
     {{$frontend := Last .}}