From 28efb6fd5020f046c1216773dd4e2f7e601f7d35 Mon Sep 17 00:00:00 2001
From: Chris Waldon <christopher.waldon.dev@gmail.com>
Date: Wed, 21 Jul 2021 16:17:41 -0400
Subject: [PATCH] feat(orchard): synchronize cache access

Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
---
 orchard/orchard.go | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/orchard/orchard.go b/orchard/orchard.go
index 98a6535..1dc4237 100644
--- a/orchard/orchard.go
+++ b/orchard/orchard.go
@@ -10,6 +10,7 @@ package orchard
 import (
 	"fmt"
 	"io"
+	"sync"
 	"time"
 
 	"git.sr.ht/~whereswaldon/forest-go"
@@ -55,7 +56,8 @@ var (
 // Nodes are persisted as schema entities and can be queried as such.
 type Orchard struct {
 	*bolt.DB
-	ReadCache *store.MemoryStore
+	cacheLock sync.RWMutex
+	readCache *store.MemoryStore
 
 	// codec zero value defaults to Arbor serialization.
 	// Can only be overriden by interal code.
@@ -94,7 +96,7 @@ func Using(db *bolt.DB, opts ...Option) (*Orchard, error) {
 	}
 	o := Orchard{
 		DB:        db,
-		ReadCache: store.NewMemoryStore(),
+		readCache: store.NewMemoryStore(),
 	}
 	for _, opt := range opts {
 		opt(&o)
@@ -185,12 +187,17 @@ func (o *Orchard) Add(node forest.Node) error {
 // Get searches for a node with the given id.
 // Present indicates whether the node exists, err indicates a failure to load it.
 func (o *Orchard) Get(nodeID *fields.QualifiedHash) (node forest.Node, present bool, err error) {
-	if n, ok, _ := o.ReadCache.Get(nodeID); ok {
+	o.cacheLock.RLock()
+	if n, ok, _ := o.readCache.Get(nodeID); ok {
+		o.cacheLock.RUnlock()
 		return n, ok, nil
 	}
+	o.cacheLock.RUnlock()
 	defer func() {
+		o.cacheLock.Lock()
+		defer o.cacheLock.Unlock()
 		if err == nil && node != nil {
-			_ = o.ReadCache.Add(node)
+			_ = o.readCache.Add(node)
 		}
 	}()
 	var (
@@ -407,6 +414,8 @@ func (o *Orchard) RemoveSubtree(id *fields.QualifiedHash) error {
 	if err != nil {
 		return err
 	}
+	o.cacheLock.Lock()
+	defer o.cacheLock.Unlock()
 	for _, child := range children {
 		if err := o.RemoveSubtree(child); err != nil {
 			return err
@@ -416,7 +425,7 @@ func (o *Orchard) RemoveSubtree(id *fields.QualifiedHash) error {
 }
 
 func (o *Orchard) delete(n forest.Node) error {
-	if err := o.ReadCache.RemoveSubtree(n.ID()); err != nil {
+	if err := o.readCache.RemoveSubtree(n.ID()); err != nil {
 		return fmt.Errorf("failed removing node %v from cache: %w", n.ID(), err)
 	}
 	id, err := o.codec.Encode(n.ID())
-- 
2.45.2