rules: replace some global vars with constants

api/v1/cmd/example-scheduler/app/app.go

@@ -88,7 +88,7 @@ func Run(cfg Config) error {
 // buildEventHandler generates and returns a handler to process events received from the subscription.
 func buildEventHandler(state *internalState, fidStore store.Singleton) events.Handler {
 	// disable brief logs when verbose logs are enabled (there's no sense logging twice!)
-	logger := controller.LogEvents().Unless(state.config.verbose)
+	logger := controller.LogEvents(nil).Unless(state.config.verbose)
 	return eventrules.Concat(
 		logAllEvents().If(state.config.verbose),
 		eventMetrics(state.metricsAPI, time.Now, state.config.summaryMetrics),

api/v1/cmd/msh/msh.go

@@ -132,7 +132,7 @@ func buildClient() calls.Caller {
 }
 
 func buildEventHandler(caller calls.Caller) events.Handler {
-	logger := controller.LogEvents()
+	logger := controller.LogEvents(nil)
 	return controller.LiftErrors().Handle(events.Handlers{
 		scheduler.Event_SUBSCRIBED: eventrules.Rules{logger, controller.TrackSubscription(fidStore, 0)},
 		scheduler.Event_OFFERS:     maybeDeclineOffers(caller).AndThen().Handle(resourceOffers(caller)),

api/v1/lib/executor/events/events_generated.go

@@ -29,10 +29,12 @@ type (
 // HandleEvent implements Handler for HandlerFunc
 func (f HandlerFunc) HandleEvent(ctx context.Context, e *executor.Event) error { return f(ctx, e) }
 
-var noopHandler = func(_ context.Context, _ *executor.Event) error { return nil }
+type noopHandler int
 
-// NoopHandler returns a HandlerFunc that does nothing and always returns nil
-func NoopHandler() HandlerFunc { return noopHandler }
+func (_ noopHandler) HandleEvent(_ context.Context, _ *executor.Event) error { return nil }
+
+// NoopHandler is a Handler that does nothing and always returns nil
+const NoopHandler = noopHandler(0)
 
 // HandleEvent implements Handler for Handlers
 func (hs Handlers) HandleEvent(ctx context.Context, e *executor.Event) (err error) {

api/v1/lib/extras/gen/handlers.go

@@ -45,10 +45,12 @@ type (
 // HandleEvent implements Handler for HandlerFunc
 func (f HandlerFunc) HandleEvent(ctx context.Context, e {{.Type "E"}}) error { return f(ctx, e) }
 
-var noopHandler = func(_ context.Context, _ {{.Type "E"}}) error { return nil }
+type noopHandler int
 
-// NoopHandler returns a HandlerFunc that does nothing and always returns nil
-func NoopHandler() HandlerFunc { return noopHandler }
+func (_ noopHandler) HandleEvent(_ context.Context, _ {{.Type "E"}}) error { return nil }
+
+// NoopHandler is a Handler that does nothing and always returns nil
+const NoopHandler = noopHandler(0)
 
 // HandleEvent implements Handler for Handlers
 func (hs Handlers) HandleEvent(ctx context.Context, e {{.Type "E"}}) (err error) {

api/v1/lib/extras/scheduler/controller/controller.go

@@ -146,5 +146,7 @@ func eventLoop(ctx context.Context, config Config, eventDecoder encoding.Decoder
 	return err
 }
 
-// DefaultHandler defaults to events.NoopHandler
-var DefaultHandler = events.NoopHandler()
+// DefaultHandler is invoked when no other handlers have been defined for the controller.
+// The current implementation does nothing.
+// TODO(jdef) a smarter default impl would decline all offers so as to avoid resource hoarding.
+const DefaultHandler = events.NoopHandler

api/v1/lib/extras/scheduler/controller/rules.go

@@ -113,17 +113,24 @@ func AckStatusUpdatesF(callerLookup func() calls.Caller) Rule {
 	}
 }
 
-var (
-	// EventLabel is, by default, logged as the first argument by EventLogger
-	EventLabel = "event"
-	// EventLogger is the logger used by the LogEvents rule generator
-	EventLogger = func(e *scheduler.Event) { log.Println(EventLabel, e) }
-)
+// DefaultEventLabel is, by default, logged as the first argument by DefaultEventLogger
+const DefaultEventLabel = "event"
+
+// DefaultEventLogger logs the event via the `log` package.
+func DefaultEventLogger(eventLabel string) func(*scheduler.Event) {
+	if eventLabel == "" {
+		return func(e *scheduler.Event) { log.Println(e) }
+	}
+	return func(e *scheduler.Event) { log.Println(eventLabel, e) }
+}
 
 // LogEvents returns a rule that logs scheduler events to the EventLogger
-func LogEvents() Rule {
+func LogEvents(f func(*scheduler.Event)) Rule {
+	if f == nil {
+		f = DefaultEventLogger(DefaultEventLabel)
+	}
 	return Rule(func(ctx context.Context, e *scheduler.Event, err error, chain Chain) (context.Context, *scheduler.Event, error) {
-		EventLogger(e)
+		f(e)
 		return chain(ctx, e, err)
 	})
 }

api/v1/lib/scheduler/events/events_generated.go

@@ -29,10 +29,12 @@ type (
 // HandleEvent implements Handler for HandlerFunc
 func (f HandlerFunc) HandleEvent(ctx context.Context, e *scheduler.Event) error { return f(ctx, e) }
 
-var noopHandler = func(_ context.Context, _ *scheduler.Event) error { return nil }
+type noopHandler int
 
-// NoopHandler returns a HandlerFunc that does nothing and always returns nil
-func NoopHandler() HandlerFunc { return noopHandler }
+func (_ noopHandler) HandleEvent(_ context.Context, _ *scheduler.Event) error { return nil }
+
+// NoopHandler is a Handler that does nothing and always returns nil
+const NoopHandler = noopHandler(0)
 
 // HandleEvent implements Handler for Handlers
 func (hs Handlers) HandleEvent(ctx context.Context, e *scheduler.Event) (err error) {