From 5298a2cabf4673e8820702d51540e102d64dd401 Mon Sep 17 00:00:00 2001
From: bryanqiu <bryanqiu@tencent.com>
Date: Thu, 7 Sep 2023 11:52:20 +0800
Subject: [PATCH] cocurrent fix

---
 cache.go | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/cache.go b/cache.go
index 38a5710..9f4e0ba 100644
--- a/cache.go
+++ b/cache.go
@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"sync"
 	"time"
 
 	"github.com/gomodule/redigo/redis"
@@ -69,7 +70,7 @@ func NewCache[T any](getter Getter[T], cfg Config) Cacher[T] {
 	if cfg.UseLocalCache {
 		c.localCache = new(localCacher[T])
 		c.localCache.cacher = c
-		c.localCache.cacheItems = map[string]*cacheItem[T]{}
+		c.localCache.cacheItems = sync.Map{} //map[string]*cacheItem[T]{}
 		c.localCache.cacheDuration = time.Duration(cfg.LocalCacheLifetimeSecond) * time.Second
 		if c.localCache.cacheDuration.Nanoseconds() == 0 {
 			c.localCache.cacheDuration = 60 * time.Second
@@ -159,9 +160,9 @@ type cacheItem[T any] struct {
 }
 
 type localCacher[T any] struct {
-	cacher        *cacher[T]
-	cacheItems    map[string]*cacheItem[T]
-	cacheDuration time.Duration
+	cacher        *cacher[T]    // parents cacher pointer
+	cacheItems    sync.Map      // map[string]*cacheItem[T]
+	cacheDuration time.Duration // cache alive duration
 }
 
 type redisCacher[T any] struct {
@@ -174,9 +175,11 @@ type redisCacher[T any] struct {
 
 func (c *localCacher[T]) GetFromCache(id string, options ...Option) (t *T, err error) {
 	// Step 1. get from map
-	var a, ok = c.cacheItems[id]
-	if !ok {
+	var a *cacheItem[T] = nil
+	if aa, ok := c.cacheItems.Load(id); !ok {
 		return nil, ErrNotFound
+	} else if a, ok = aa.(*cacheItem[T]); !ok {
+		panic("unreachable code, inner item type must be '*cacheItem[T]'")
 	}
 
 	// Step 2. check is expired or not
@@ -189,8 +192,7 @@ func (c *localCacher[T]) GetFromCache(id string, options ...Option) (t *T, err e
 				err = ErrExpired
 			} else {
 				log.Infof("cache(%s) is in local cache but expired, we delete it", id)
-				//TODO: cocurrent
-				delete(c.cacheItems, id)
+				c.cacheItems.Delete(id)
 				return nil, ErrNotFound
 			}
 		}
@@ -206,7 +208,7 @@ func (c *localCacher[T]) GetFromCache(id string, options ...Option) (t *T, err e
 	if err == ErrExpired {
 		return a.Data, ErrExpired
 	} else if err != nil {
-		panic("unreachable code")
+		panic("unreachable code: only ErrExpired error valid when data exist")
 	}
 	return a.Data, nil
 }
@@ -219,7 +221,7 @@ func (c *localCacher[T]) SetIntoCache(id string, t *T, options ...Option) (err e
 	} else {
 		newitem.CreateTime = time.Now()
 	}
-	c.cacheItems[id] = newitem
+	c.cacheItems.Store(id, newitem)
 	return nil
 }