fix(redis-strings): prevent mapping tables deletion before cache purge (#3)

This PR addresses a critical data consistency issue in the delete method where
mapping table entries could be removed before the cache was successfully cleared.
By reversing the operation order to clear cache after mapping tables are updated,
we ensure that even in failure scenarios, the cache can still be revalidated
through tags.

Previously, concurrent operations in Promise.all could lead to orphaned cache
entries with no way to revalidate them via tags, potentially serving stale data
indefinitely. This change provides a more robust cache invalidation strategy
that prioritizes data consistency over performance.

Author: Dwlad90

packages/nextjs-cache-handler/package.json

@@ -29,7 +29,7 @@
         "dist/redis-strings.d.ts"
       ],
       "buffer-string-decorator": [
-        "buffer-string-decorator.d.ts"
+        "dist/buffer-string-decorator.d.ts"
       ]
     }
   },

packages/nextjs-cache-handler/src/handlers/redis-strings.ts

@@ -102,7 +102,7 @@ export default function createHandler({
       return;
     }
 
-    const deleteKeysOperation = client.unlink(
+    await client.unlink(
       getTimeoutRedisCommandOptions(timeoutMs),
       keysToDelete,
     );
@@ -120,7 +120,6 @@ export default function createHandler({
     );
 
     await Promise.all([
-      deleteKeysOperation,
       updateTtlOperation,
       updateTagsOperation,
     ]);
@@ -162,6 +161,11 @@ export default function createHandler({
       return;
     }
 
+    await client.unlink(
+      getTimeoutRedisCommandOptions(timeoutMs),
+      keysToDelete,
+    );
+
     const updateTtlOperation = client.hDel(
       {
         isolated: true,
@@ -180,13 +184,7 @@ export default function createHandler({
       tagsAndTtlToDelete,
     );
 
-    const deleteKeysOperation = client.unlink(
-      getTimeoutRedisCommandOptions(timeoutMs),
-      keysToDelete,
-    );
-
     await Promise.all([
-      deleteKeysOperation,
       updateTagsOperation,
       updateTtlOperation,
     ]);
@@ -251,6 +249,30 @@ export default function createHandler({
       let expireOperation: Promise<boolean> | undefined;
       const lifespan = cacheHandlerValue.lifespan;
 
+      const setTagsOperation =
+        cacheHandlerValue.tags.length > 0
+          ? client.hSet(
+              options,
+              keyPrefix + sharedTagsKey,
+              key,
+              JSON.stringify(cacheHandlerValue.tags),
+            )
+          : undefined;
+
+      const setSharedTtlOperation = lifespan
+        ? client.hSet(
+            options,
+            keyPrefix + sharedTagsTtlKey,
+            key,
+            lifespan.expireAt,
+          )
+        : undefined;
+
+        await Promise.all([
+          setTagsOperation,
+          setSharedTtlOperation,
+        ]);
+
       switch (keyExpirationStrategy) {
         case "EXAT": {
           setOperation = client.set(
@@ -284,31 +306,10 @@ export default function createHandler({
         }
       }
 
-      const setTagsOperation =
-        cacheHandlerValue.tags.length > 0
-          ? client.hSet(
-              options,
-              keyPrefix + sharedTagsKey,
-              key,
-              JSON.stringify(cacheHandlerValue.tags),
-            )
-          : undefined;
-
-      const setSharedTtlOperation = lifespan
-        ? client.hSet(
-            options,
-            keyPrefix + sharedTagsTtlKey,
-            key,
-            lifespan.expireAt,
-          )
-        : undefined;
-
-      await Promise.all([
-        setOperation,
-        expireOperation,
-        setTagsOperation,
-        setSharedTtlOperation,
-      ]);
+        await Promise.all([
+          setOperation,
+          expireOperation,
+        ]);
     },
     async revalidateTag(tag) {
       assertClientIsReady();
@@ -329,11 +330,12 @@ export default function createHandler({
       await Promise.all([revalidateTags(tag), revalidateSharedKeys()]);
     },
     async delete(key) {
+      await client.unlink(
+        getTimeoutRedisCommandOptions(timeoutMs),
+        keyPrefix + key,
+      );
+
       await Promise.all([
-        client.unlink(
-          getTimeoutRedisCommandOptions(timeoutMs),
-          keyPrefix + key,
-        ),
         client.hDel(keyPrefix + sharedTagsKey, key),
         client.hDel(keyPrefix + sharedTagsTtlKey, key),
       ]);