graph/db: let ChannelGraph init the graphCache

In this commit, we let the ChannelGraph be responsible for populating
the graphCache and then passing it to the KVStore. This is a first step
in moving the graphCache completely out of the KVStore layer.

graph/db/options.go

@@ -20,6 +20,47 @@ const (
 	DefaultPreAllocCacheNumNodes = 15000
 )
 
+// chanGraphOptions holds parameters for tuning and customizing the
+// ChannelGraph.
+type chanGraphOptions struct {
+	// useGraphCache denotes whether the in-memory graph cache should be
+	// used or a fallback version that uses the underlying database for
+	// path finding.
+	useGraphCache bool
+
+	// preAllocCacheNumNodes is the number of nodes we expect to be in the
+	// graph cache, so we can pre-allocate the map accordingly.
+	preAllocCacheNumNodes int
+}
+
+// defaultChanGraphOptions returns a new chanGraphOptions instance populated
+// with default values.
+func defaultChanGraphOptions() *chanGraphOptions {
+	return &chanGraphOptions{
+		useGraphCache:         true,
+		preAllocCacheNumNodes: DefaultPreAllocCacheNumNodes,
+	}
+}
+
+// ChanGraphOption describes the signature of a functional option that can be
+// used to customize a ChannelGraph instance.
+type ChanGraphOption func(*chanGraphOptions)
+
+// WithUseGraphCache sets whether the in-memory graph cache should be used.
+func WithUseGraphCache(use bool) ChanGraphOption {
+	return func(o *chanGraphOptions) {
+		o.useGraphCache = use
+	}
+}
+
+// WithPreAllocCacheNumNodes sets the number of nodes we expect to be in the
+// graph cache, so we can pre-allocate the map accordingly.
+func WithPreAllocCacheNumNodes(n int) ChanGraphOption {
+	return func(o *chanGraphOptions) {
+		o.preAllocCacheNumNodes = n
+	}
+}
+
 // KVStoreOptions holds parameters for tuning and customizing a graph.DB.
 type KVStoreOptions struct {
 	// RejectCacheSize is the maximum number of rejectCacheEntries to hold
@@ -34,15 +75,6 @@ type KVStoreOptions struct {
 	// wait before attempting to commit a pending set of updates.
 	BatchCommitInterval time.Duration
 
-	// PreAllocCacheNumNodes is the number of nodes we expect to be in the
-	// graph cache, so we can pre-allocate the map accordingly.
-	PreAllocCacheNumNodes int
-
-	// UseGraphCache denotes whether the in-memory graph cache should be
-	// used or a fallback version that uses the underlying database for
-	// path finding.
-	UseGraphCache bool
-
 	// NoMigration specifies that underlying backend was opened in read-only
 	// mode and migrations shouldn't be performed. This can be useful for
 	// applications that use the channeldb package as a library.
@@ -52,11 +84,9 @@ type KVStoreOptions struct {
 // DefaultOptions returns a KVStoreOptions populated with default values.
 func DefaultOptions() *KVStoreOptions {
 	return &KVStoreOptions{
-		RejectCacheSize:       DefaultRejectCacheSize,
-		ChannelCacheSize:      DefaultChannelCacheSize,
-		PreAllocCacheNumNodes: DefaultPreAllocCacheNumNodes,
-		UseGraphCache:         true,
-		NoMigration:           false,
+		RejectCacheSize:  DefaultRejectCacheSize,
+		ChannelCacheSize: DefaultChannelCacheSize,
+		NoMigration:      false,
 	}
 }
 
@@ -78,13 +108,6 @@ func WithChannelCacheSize(n int) KVStoreOptionModifier {
 	}
 }
 
-// WithPreAllocCacheNumNodes sets the PreAllocCacheNumNodes to n.
-func WithPreAllocCacheNumNodes(n int) KVStoreOptionModifier {
-	return func(o *KVStoreOptions) {
-		o.PreAllocCacheNumNodes = n
-	}
-}
-
 // WithBatchCommitInterval sets the batch commit interval for the interval batch
 // schedulers.
 func WithBatchCommitInterval(interval time.Duration) KVStoreOptionModifier {
@@ -92,10 +115,3 @@ func WithBatchCommitInterval(interval time.Duration) KVStoreOptionModifier {
 		o.BatchCommitInterval = interval
 	}
 }
-
-// WithUseGraphCache sets the UseGraphCache option to the given value.
-func WithUseGraphCache(use bool) KVStoreOptionModifier {
-	return func(o *KVStoreOptions) {
-		o.UseGraphCache = use
-	}
-}