Cache: Allow entries to be explicitly deleted

server/modules/filter/cache/cache_storage_api.h

@@ -123,6 +123,17 @@ typedef struct cache_storage_api
     cache_result_t (*putValue)(CACHE_STORAGE* storage,
                                const char* key,
                                const GWBUF* value);
+
+    /**
+     * Delete a value from the cache.
+     *
+     * @param storage    Pointer to a CACHE_STORAGE.
+     * @param key        A key generated with getKey.
+     * @return CACHE_RESULT_OK if item was successfully deleted.  Note that
+     *         CACHE_RESULT_OK may be returned also if the entry was not present.
+     */
+    cache_result_t (*delValue)(CACHE_STORAGE* storage,
+                               const char* key);
 } CACHE_STORAGE_API;
 
 #define CACHE_STORAGE_ENTRY_POINT "CacheGetStorageAPI"

server/modules/filter/cache/storage/storage_rocksdb/rocksdbstorage.cc

@@ -476,3 +476,14 @@ cache_result_t RocksDBStorage::putValue(const char* pKey, const GWBUF* pValue)
 
     return status.ok() ? CACHE_RESULT_OK : CACHE_RESULT_ERROR;
 }
+
+cache_result_t RocksDBStorage::delValue(const char* pKey)
+{
+    ss_dassert(pKey);
+
+    rocksdb::Slice key(pKey, ROCKSDB_KEY_LENGTH);
+
+    rocksdb::Status status = m_sDb->Delete(writeOptions(), key);
+
+    return status.ok() ? CACHE_RESULT_OK : CACHE_RESULT_ERROR;
+}

server/modules/filter/cache/storage/storage_rocksdb/rocksdbstorage.h

@@ -32,6 +32,7 @@ public:
     cache_result_t getKey(const char* zDefaultDB, const GWBUF* pQuery, char* pKey);
     cache_result_t getValue(const char* pKey, uint32_t flags, GWBUF** ppResult);
     cache_result_t putValue(const char* pKey, const GWBUF* pValue);
+    cache_result_t delValue(const char* pKey);
 
 private:
     RocksDBStorage(std::unique_ptr<rocksdb::DBWithTTL>& sDb,

server/modules/filter/cache/storage/storage_rocksdb/storage_rocksdb.cc

@@ -147,6 +147,34 @@ cache_result_t putValue(CACHE_STORAGE* pStorage,
     return result;
 }
 
+cache_result_t delValue(CACHE_STORAGE* pStorage,
+                        const char* pKey)
+{
+    ss_dassert(pStorage);
+    ss_dassert(pKey);
+
+    cache_result_t result = CACHE_RESULT_ERROR;
+
+    try
+    {
+        result = reinterpret_cast<RocksDBStorage*>(pStorage)->delValue(pKey);
+    }
+    catch (const std::bad_alloc&)
+    {
+        MXS_OOM();
+    }
+    catch (const std::exception& x)
+    {
+        MXS_ERROR("Standard exception caught: %s", x.what());
+    }
+    catch (...)
+    {
+        MXS_ERROR("Unknown exception caught.");
+    }
+
+    return result;
+}
+
 }
 
 extern "C"
@@ -161,7 +189,8 @@ CACHE_STORAGE_API* CacheGetStorageAPI()
             freeInstance,
             getKey,
             getValue,
-            putValue
+            putValue,
+            delValue,
         };
 
     return &api;