Inject hooks to executor constructor.

Move creation and configuration of hooks to main function.
This will enable users to simply replace main.go with
their own implementation to use custom hooks.
Hooks configuration is indepenedent from Executor configuration
so there is no need to keep it in Executor.

cmd/executor/main.go

@@ -11,6 +11,9 @@ import (
 	"github.com/mesos/mesos-go/api/v1/lib/executor/config"
 
 	"github.com/allegro/mesos-executor"
+	"github.com/allegro/mesos-executor/hook"
+	"github.com/allegro/mesos-executor/hook/consul"
+	"github.com/allegro/mesos-executor/hook/vaas"
 	"github.com/allegro/mesos-executor/runenv"
 )
 
@@ -75,14 +78,36 @@ func initSentry(config executor.Config) error {
 	return nil
 }
 
+func createHooks() []hook.Hook {
+	var consulConfig consul.Config
+	if err := envconfig.Process(environmentPrefix, &consulConfig); err != nil {
+		log.WithError(err).Fatal("Failed to load Consul hook configuration")
+	}
+	consulHook, err := consul.NewHook(consulConfig)
+	if err != nil {
+		log.WithError(err).Fatalf("Error loading Consul hook %s", err)
+	}
+
+	var vaasConfig vaas.Config
+	if err := envconfig.Process(environmentPrefix, &vaasConfig); err != nil {
+		log.WithError(err).Fatal("Failed to load VaaS hook configuration")
+	}
+	vaasHook, err := vaas.NewHook(vaasConfig)
+	if err != nil {
+		log.WithError(err).Fatalf("Error loading VaaS service hook %s", err)
+	}
+
+	return []hook.Hook{consulHook, vaasHook}
+}
+
 func main() {
 	log.Infof("Allegro Mesos Executor (version: %s)", Version)
 	cfg, err := config.FromEnv()
 	if err != nil {
 		log.WithError(err).Fatal("Failed to load Mesos configuration")
 	}
 	Config.MesosConfig = cfg
-	exec := executor.NewExecutor(Config)
+	exec := executor.NewExecutor(Config, createHooks()...)
 	if err := exec.Start(); err != nil {
 		log.WithError(err).Fatal("Executor exited with error")
 	}

executor.go

@@ -21,8 +21,6 @@ import (
 	"github.com/mesos/mesos-go/api/v1/lib/httpcli"
 
 	"github.com/allegro/mesos-executor/hook"
-	"github.com/allegro/mesos-executor/hook/consul"
-	"github.com/allegro/mesos-executor/hook/vaas"
 	"github.com/allegro/mesos-executor/mesosutils"
 	"github.com/allegro/mesos-executor/state"
 )
@@ -47,16 +45,6 @@ type Config struct {
 	// Mesos framework configuration
 	MesosConfig config.Config `ignore:"true"`
 
-	// Varnish as a Service API url
-	VaasAPIHost string `default:"" envconfig:"vaas_host"`
-	// Varnish as a Service username
-	VaasAPIUsername string `default:"" envconfig:"vaas_username"`
-	// Varnish as a Service access token
-	VaasAPIKey string `default:"" envconfig:"vaas_token"`
-
-	// Consul ACL Token
-	ConsulToken string `default:"" envconfig:"consul_token"`
-
 	// SentryDSN is an address used for sending logs to Sentry
 	SentryDSN string `split_words:"true"`
 
@@ -124,8 +112,8 @@ const (
 	Launch
 )
 
-// NewExecutor creates new instance of executor configured with by `cfg`.
-func NewExecutor(cfg Config) *Executor {
+// NewExecutor creates new instance of executor configured with by `cfg` with hooks
+func NewExecutor(cfg Config, hooks ...hook.Hook) *Executor {
 
 	log.Info("Initializing executor with following configuration:")
 	log.Infof("AgentEndpoint               = %s", cfg.MesosConfig.AgentEndpoint)
@@ -145,27 +133,13 @@ func NewExecutor(cfg Config) *Executor {
 		context:       ctx,
 		contextCancel: ctxCancel,
 		events:        make(chan Event),
-		hookManager:   newHookManager(cfg),
+		hookManager:   hook.Manager{hooks},
 		stateUpdater:  state.BufferedUpdater(cfg.MesosConfig, cfg.StateUpdateBufferSize),
 		clock:         systemClock{},
 		random:        newRandom(),
 	}
 }
 
-func newHookManager(config Config) hook.Manager {
-	vaasHook, err := vaas.NewHook(config.VaasAPIHost, config.VaasAPIUsername, config.VaasAPIKey)
-	if err != nil {
-		log.WithError(err).Fatalf("Error loading VaaS service hook %s", err)
-	}
-
-	consulHook, err := consul.NewHook(config.ConsulToken)
-	if err != nil {
-		log.WithError(err).Fatalf("Error loading Consul hook %s", err)
-	}
-
-	return hook.Manager{Hooks: []hook.Hook{vaasHook, consulHook}}
-}
-
 // Start registers executor in Mesos agent and waits for events from it.
 func (e *Executor) Start() error {
 

hook/consul/hook.go

@@ -37,6 +37,12 @@ type Hook struct {
 	serviceInstances []instance
 }
 
+// Config is Consul hook configuration settable from environment
+type Config struct {
+	// Consul ACL Token
+	ConsulToken string `default:"" envconfig:"consul_token"`
+}
+
 // HandleEvent calls appropriate hook functions that correspond to supported
 // event types. Unsupported events are ignored.
 func (h *Hook) HandleEvent(event hook.Event) error {
@@ -206,9 +212,9 @@ func generateURL(info *mesos.HealthCheck_HTTPCheckInfo, port int) string {
 }
 
 // NewHook creates new Consul hook that is responsible for graceful Consul deregistration.
-func NewHook(token string) (hook.Hook, error) {
+func NewHook(cfg Config) (hook.Hook, error) {
 	config := api.DefaultConfig()
-	config.Token = token
+	config.Token = cfg.ConsulToken
 	client, err := api.NewClient(config)
 	if err != nil {
 		return nil, err

hook/vaas/hook.go

@@ -31,6 +31,16 @@ type Hook struct {
 	client    Client
 }
 
+// Config is Varnish configuration settable from environment
+type Config struct {
+	// Varnish as a Service API url
+	VaasAPIHost string `default:"" envconfig:"vaas_host"`
+	// Varnish as a Service username
+	VaasAPIUsername string `default:"" envconfig:"vaas_username"`
+	// Varnish as a Service access token
+	VaasAPIKey string `default:"" envconfig:"vaas_token"`
+}
+
 // RegisterBackend adds new backend to VaaS if it does not exist.
 func (sh *Hook) RegisterBackend(taskInfo mesos.TaskInfo) error {
 	handyTaskInfo := mesosutils.TaskInfo{TaskInfo: taskInfo}
@@ -200,12 +210,12 @@ func (sh *Hook) HandleEvent(event hook.Event) error {
 }
 
 // NewHook returns new instance of Hook.
-func NewHook(apiHost string, apiUsername string, apiKey string) (*Hook, error) {
+func NewHook(cfg Config) (*Hook, error) {
 	return &Hook{
 		client: NewClient(
-			apiHost,
-			apiUsername,
-			apiKey,
+			cfg.VaasAPIHost,
+			cfg.VaasAPIUsername,
+			cfg.VaasAPIKey,
 		),
 	}, nil
 }