Add config service

Author: jakewright

home-automation/03-config/config.yaml

@@ -0,0 +1,9 @@
+base:
+  apiGateway: http://service.api-gateway
+  redis:
+    host: redis
+    port: 6379
+
+service.registry.device:
+  database: /data/devices.db
+  apiGateway: somethingNew

home-automation/03-config/controller/controller.go

@@ -0,0 +1,42 @@
+package controller
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+
+	"github.com/gorilla/mux"
+	"github.com/jakewright/tutorials/home-automation/03-config/domain"
+)
+
+// Controller exports the handlers for the endpoints
+type Controller struct {
+	Config *domain.Config
+}
+
+// ReadConfig writes the config for the given service to the ResponseWriter
+func (c *Controller) ReadConfig(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "application/json; charset=UTF-8")
+
+	vars := mux.Vars(r)
+	serviceName, ok := vars["serviceName"]
+	if !ok {
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintf(w, "error")
+	}
+
+	config, err := c.Config.Get(serviceName)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "error")
+	}
+
+	rsp, err := json.Marshal(&config)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		fmt.Fprintf(w, "error")
+	}
+
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintf(w, string(rsp))
+}

home-automation/03-config/domain/config.go

@@ -0,0 +1,94 @@
+package domain
+
+import (
+	"fmt"
+	"sync"
+
+	"gopkg.in/yaml.v2"
+)
+
+// Config is an abstraction around the map that holds the config values
+type Config struct {
+	config map[string]interface{}
+	lock   sync.RWMutex
+}
+
+// SetFromBytes sets the internal config based on a byte array of YAML
+func (c *Config) SetFromBytes(data []byte) error {
+	var rawConfig interface{}
+	if err := yaml.Unmarshal(data, &rawConfig); err != nil {
+		return err
+	}
+
+	untypedConfig, ok := rawConfig.(map[interface{}]interface{})
+	if !ok {
+		return fmt.Errorf("config is not a map")
+	}
+
+	config, err := convertKeysToStrings(untypedConfig)
+	if err != nil {
+		return err
+	}
+
+	c.lock.Lock()
+	defer c.lock.Unlock()
+
+	c.config = config
+	return nil
+}
+
+// Get returns the config for a particular service
+func (c *Config) Get(serviceName string) (map[string]interface{}, error) {
+	c.lock.RLock()
+	defer c.lock.RUnlock()
+
+	a, ok := c.config["base"].(map[string]interface{})
+	if !ok {
+		return nil, fmt.Errorf("base config is not a map")
+	}
+
+	// If no config is defined for the service
+	if _, ok = c.config[serviceName]; !ok {
+		// Return the base config
+		return a, nil
+	}
+
+	b, ok := c.config[serviceName].(map[string]interface{})
+	if !ok {
+		return nil, fmt.Errorf("service %q config is not a map", serviceName)
+	}
+
+	// Merge the maps with the service config taking precedence
+	config := make(map[string]interface{})
+	for k, v := range a {
+		config[k] = v
+	}
+	for k, v := range b {
+		config[k] = v
+	}
+
+	return config, nil
+}
+
+func convertKeysToStrings(m map[interface{}]interface{}) (map[string]interface{}, error) {
+	n := make(map[string]interface{})
+
+	for k, v := range m {
+		str, ok := k.(string)
+		if !ok {
+			return nil, fmt.Errorf("config key is not a string")
+		}
+
+		if vMap, ok := v.(map[interface{}]interface{}); ok {
+			var err error
+			v, err = convertKeysToStrings(vMap)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		n[str] = v
+	}
+
+	return n, nil
+}

home-automation/03-config/main.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"log"
+	"time"
+
+	"github.com/jakewright/muxinator"
+
+	"github.com/jakewright/tutorials/home-automation/03-config/controller"
+	"github.com/jakewright/tutorials/home-automation/03-config/domain"
+	"github.com/jakewright/tutorials/home-automation/03-config/service"
+)
+
+func main() {
+	config := domain.Config{}
+
+	configService := service.ConfigService{
+		Config:   &config,
+		Location: "config.yaml",
+	}
+
+	go configService.Watch(time.Second * 30)
+
+	c := controller.Controller{
+		Config: &config,
+	}
+
+	router := muxinator.NewRouter()
+	router.Get("/read/{serviceName}", c.ReadConfig)
+	log.Fatal(router.ListenAndServe(":8080"))
+}

home-automation/03-config/service/service.go

@@ -0,0 +1,41 @@
+package service
+
+import (
+	"io/ioutil"
+	"log"
+	"time"
+
+	"github.com/jakewright/tutorials/home-automation/03-config/domain"
+)
+
+type ConfigService struct {
+	Config   *domain.Config
+	Location string
+}
+
+// Watch reloads the config every d duration
+func (s *ConfigService) Watch(d time.Duration) {
+	for {
+		err := s.Reload()
+		if err != nil {
+			log.Print(err)
+		}
+
+		time.Sleep(d)
+	}
+}
+
+// Reload reads the config and applies changes
+func (s *ConfigService) Reload() error {
+	data, err := ioutil.ReadFile(s.Location)
+	if err != nil {
+		return err
+	}
+
+	err = s.Config.SetFromBytes(data)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}