Modules callbacks for lazy free effort, and unlink (#7912)

Add two optional callbacks to the RedisModuleTypeMethods structure, which is `free_effort`
and `unlink`. the `free_effort` callback indicates the effort required to free a module memory.
Currently, if the effort exceeds LAZYFREE_THRESHOLD, the module memory may be released
asynchronously. the `unlink` callback indicates the key has been removed from the DB by redis, and
may soon be freed by a background thread.

Add `lazyfreed_objects` info field, which represents the number of objects that have been
lazyfreed since redis was started.

Add `RM_GetTypeMethodVersion` API, which return the current redis-server runtime value of
`REDISMODULE_TYPE_METHOD_VERSION`. You can use that when calling `RM_CreateDataType` to know
which fields of RedisModuleTypeMethods are gonna be supported and which will be ignored.

1 files changed, 10 insertions, 1 deletions

diff --git a/src/redismodule.h b/src/redismodule.h
index ca0a756c7..0f7134549 100644
--- a/src/redismodule.h
+++ b/src/redismodule.h
@@ -14,6 +14,10 @@
 /* API versions. */
 #define REDISMODULE_APIVER_1 1
 
+/* Version of the RedisModuleTypeMethods structure. Once the RedisModuleTypeMethods 
+ * structure is changed, this version number needs to be changed synchronistically. */
+#define REDISMODULE_TYPE_METHOD_VERSION 3
+
 /* API flags and constants */
 #define REDISMODULE_READ (1<<0)
 #define REDISMODULE_WRITE (1<<1)
@@ -485,6 +489,8 @@ typedef void (*RedisModuleTypeRewriteFunc)(RedisModuleIO *aof, RedisModuleString
 typedef size_t (*RedisModuleTypeMemUsageFunc)(const void *value);
 typedef void (*RedisModuleTypeDigestFunc)(RedisModuleDigest *digest, void *value);
 typedef void (*RedisModuleTypeFreeFunc)(void *value);
+typedef size_t (*RedisModuleTypeFreeEffortFunc)(RedisModuleString *key, const void *value);
+typedef void (*RedisModuleTypeUnlinkFunc)(RedisModuleString *key, const void *value);
 typedef void (*RedisModuleClusterMessageReceiver)(RedisModuleCtx *ctx, const char *sender_id, uint8_t type, const unsigned char *payload, uint32_t len);
 typedef void (*RedisModuleTimerProc)(RedisModuleCtx *ctx, void *data);
 typedef void (*RedisModuleCommandFilterFunc) (RedisModuleCommandFilterCtx *filter);
@@ -494,7 +500,6 @@ typedef void (*RedisModuleScanCB)(RedisModuleCtx *ctx, RedisModuleString *keynam
 typedef void (*RedisModuleScanKeyCB)(RedisModuleKey *key, RedisModuleString *field, RedisModuleString *value, void *privdata);
 typedef void (*RedisModuleUserChangedFunc) (uint64_t client_id, void *privdata);
 
-#define REDISMODULE_TYPE_METHOD_VERSION 2
 typedef struct RedisModuleTypeMethods {
     uint64_t version;
     RedisModuleTypeLoadFunc rdb_load;
@@ -506,6 +511,8 @@ typedef struct RedisModuleTypeMethods {
     RedisModuleTypeAuxLoadFunc aux_load;
     RedisModuleTypeAuxSaveFunc aux_save;
     int aux_save_triggers;
+    RedisModuleTypeFreeEffortFunc free_effort;
+    RedisModuleTypeUnlinkFunc unlink;
 } RedisModuleTypeMethods;
 
 #define REDISMODULE_GET_API(name) \
@@ -706,6 +713,7 @@ REDISMODULE_API int (*RedisModule_GetContextFlagsAll)() REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_GetKeyspaceNotificationFlagsAll)() REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_IsSubEventSupported)(RedisModuleEvent event, uint64_t subevent) REDISMODULE_ATTR;
 REDISMODULE_API int (*RedisModule_GetServerVersion)() REDISMODULE_ATTR;
+REDISMODULE_API int (*RedisModule_GetTypeMethodVersion)() REDISMODULE_ATTR;
 
 /* Experimental APIs */
 #ifdef REDISMODULE_EXPERIMENTAL_API
@@ -956,6 +964,7 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(GetKeyspaceNotificationFlagsAll);
     REDISMODULE_GET_API(IsSubEventSupported);
     REDISMODULE_GET_API(GetServerVersion);
+    REDISMODULE_GET_API(GetTypeMethodVersion);
 
 #ifdef REDISMODULE_EXPERIMENTAL_API
     REDISMODULE_GET_API(GetThreadSafeContext);