add initial support for async error callback

index/scorch/event.go

@@ -16,6 +16,10 @@ package scorch
 
 import "time"
 
+// RegistryAsyncErrorCallbacks should be treated as read-only after
+// process init()'ialization.
+var RegistryAsyncErrorCallbacks = map[string]func(error){}
+
 // RegistryEventCallbacks should be treated as read-only after
 // process init()'ialization.
 var RegistryEventCallbacks = map[string]func(Event){}

index/scorch/merge.go

@@ -16,7 +16,6 @@ package scorch
 
 import (
 	"fmt"
-	"log"
 	"os"
 	"sync/atomic"
 	"time"
@@ -48,7 +47,7 @@ OUTER:
 				// lets get started
 				err := s.planMergeAtSnapshot(ourSnapshot)
 				if err != nil {
-					log.Printf("merging err: %v", err)
+					s.fireAsyncError(fmt.Errorf("merging err: %v", err))
 					_ = ourSnapshot.DecRef()
 					continue OUTER
 				}

index/scorch/persister.go

@@ -74,7 +74,7 @@ OUTER:
 				close(ch)
 			}
 			if err != nil {
-				log.Printf("got err persisting snapshot: %v", err)
+				s.fireAsyncError(fmt.Errorf("got err persisting snapshot: %v", err))
 				_ = ourSnapshot.DecRef()
 				continue OUTER
 			}
@@ -446,13 +446,13 @@ func (p uint64Descending) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }
 func (s *Scorch) removeOldData() {
 	removed, err := s.removeOldBoltSnapshots()
 	if err != nil {
-		log.Printf("got err removing old bolt snapshots: %v", err)
+		s.fireAsyncError(fmt.Errorf("got err removing old bolt snapshots: %v", err))
 	}
 
 	if removed > 0 {
 		err = s.removeOldZapFiles()
 		if err != nil {
-			log.Printf("got err removing old zap files: %v", err)
+			s.fireAsyncError(fmt.Errorf("got err removing old zap files: %v", err))
 		}
 	}
 }

index/scorch/scorch.go

@@ -72,7 +72,8 @@ type Scorch struct {
 	rootBolt           *bolt.DB
 	asyncTasks         sync.WaitGroup
 
-	onEvent func(event Event)
+	onEvent      func(event Event)
+	onAsyncError func(err error)
 }
 
 func NewScorch(storeName string,
@@ -100,6 +101,10 @@ func NewScorch(storeName string,
 	if ok {
 		rv.onEvent = RegistryEventCallbacks[ecbName]
 	}
+	aecbName, ok := config["asyncErrorCallbackName"].(string)
+	if ok {
+		rv.onAsyncError = RegistryAsyncErrorCallbacks[aecbName]
+	}
 	return rv, nil
 }
 
@@ -109,6 +114,12 @@ func (s *Scorch) fireEvent(kind EventKind, dur time.Duration) {
 	}
 }
 
+func (s *Scorch) fireAsyncError(err error) {
+	if s.onAsyncError != nil {
+		s.onAsyncError(err)
+	}
+}
+
 func (s *Scorch) Open() error {
 	var ok bool
 	s.path, ok = s.config["path"].(string)