Cache: Make it possible to specify thread model for storage

server/modules/filter/cache/cache_storage_api.h

@@ -37,6 +37,12 @@ typedef enum cache_flags
     CACHE_FLAGS_INCLUDE_STALE = 0x01,
 } cache_flags_t;
 
+typedef enum cache_thread_model
+{
+    CACHE_THREAD_MODEL_ST  = 0x1,
+    CACHE_THREAD_MODEL_MT  = 0x2,
+} cache_thread_model_t;
+
 typedef void* CACHE_STORAGE;
 
 enum
@@ -58,6 +64,10 @@ typedef struct cache_storage_api
      * create the actual storage, initialize it and prepare to put and get
      * cache items.
      *
+     * @param model Whether the storage will be used in a single thread or
+     *              multi thread context. In the latter case the storage must
+     *              perform thread synchronization as appropriate, in the former
+     *              case it need not.
      * @param name  The name of the cache instance.
      * @param ttl   Time to live; number of seconds the value is valid.
      * @param argc  The number of elements in the argv array.
@@ -66,7 +76,8 @@ typedef struct cache_storage_api
      * @return A new cache instance, or NULL if the instance could not be
      *         created.
      */
-    CACHE_STORAGE* (*createInstance)(const char *name,
+    CACHE_STORAGE* (*createInstance)(cache_thread_model_t model,
+                                     const char *name,
                                      uint32_t ttl,
                                      int argc, char* argv[]);
 

server/modules/filter/cache/cachefilter.h

@@ -16,6 +16,7 @@
 
 #include <maxscale/cdefs.h>
 #include <limits.h>
+#include <exception>
 #include <maxscale/hashtable.h>
 #include <maxscale/spinlock.h>
 #include "rules.h"

server/modules/filter/cache/cachemt.cc

@@ -12,8 +12,6 @@
  */
 
 #include "cachemt.h"
-#include <new>
-#include <maxscale/spinlock.h>
 #include "storage.h"
 #include "storagefactory.h"
 
@@ -46,7 +44,7 @@ CacheMT* CacheMT::Create(const char* zName, CACHE_CONFIG& config)
         int argc = config.storage_argc;
         char** argv = config.storage_argv;
 
-        Storage* pStorage = pFactory->createStorage(zName, ttl, argc, argv);
+        Storage* pStorage = pFactory->createStorage(CACHE_THREAD_MODEL_MT, zName, ttl, argc, argv);
 
         if (pStorage)
         {

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

@@ -23,7 +23,10 @@ bool initialize()
     return RocksDBStorage::Initialize();
 }
 
-CACHE_STORAGE* createInstance(const char* zName, uint32_t ttl, int argc, char* argv[])
+CACHE_STORAGE* createInstance(cache_thread_model_t, // Ignored, RocksDB always MT safe.
+                              const char* zName,
+                              uint32_t ttl,
+                              int argc, char* argv[])
 {
     ss_dassert(zName);
 

server/modules/filter/cache/storagefactory.cc

@@ -131,7 +131,8 @@ StorageFactory* StorageFactory::Open(const char* zName)
     return pFactory;
 }
 
-Storage* StorageFactory::createStorage(const char* zName,
+Storage* StorageFactory::createStorage(cache_thread_model_t model,
+                                       const char* zName,
                                        uint32_t ttl,
                                        int argc, char* argv[])
 {
@@ -139,7 +140,7 @@ Storage* StorageFactory::createStorage(const char* zName,
     ss_dassert(m_pApi);
 
     Storage* pStorage = 0;
-    CACHE_STORAGE* pRawStorage = m_pApi->createInstance(zName, ttl, argc, argv);
+    CACHE_STORAGE* pRawStorage = m_pApi->createInstance(model, zName, ttl, argc, argv);
 
     if (pRawStorage)
     {

server/modules/filter/cache/storagefactory.h

@@ -26,7 +26,8 @@ public:
 
     static StorageFactory* Open(const char* zName);
 
-    Storage* createStorage(const char* zName,
+    Storage* createStorage(cache_thread_model_t model,
+                           const char* zName,
                            uint32_t ttl,
                            int argc, char* argv[]);