Add module event for repl-diskless-load swapdb

src/db.c

@@ -477,6 +477,10 @@ dbBackup *backupDb(void) {
             sizeof(server.cluster->slots_keys_count));
     }
 
+    moduleFireServerEvent(REDISMODULE_EVENT_REPL_BACKUP,
+                          REDISMODULE_SUBEVENT_REPL_BACKUP_CREATE,
+                          NULL);
+
     return backup;
 }
 
@@ -498,6 +502,10 @@ void discardDbBackup(dbBackup *buckup, int flags, void(callback)(void*)) {
     /* Release buckup. */
     zfree(buckup->dbarray);
     zfree(buckup);
+
+    moduleFireServerEvent(REDISMODULE_EVENT_REPL_BACKUP,
+                          REDISMODULE_SUBEVENT_REPL_BACKUP_DISCARD,
+                          NULL);
 }
 
 /* Restore the previously created backup (discarding what currently resides
@@ -526,6 +534,10 @@ void restoreDbBackup(dbBackup *buckup) {
     /* Release buckup. */
     zfree(buckup->dbarray);
     zfree(buckup);
+
+    moduleFireServerEvent(REDISMODULE_EVENT_REPL_BACKUP,
+                          REDISMODULE_SUBEVENT_REPL_BACKUP_RESTORE,
+                          NULL);
 }
 
 int selectDb(client *c, int id) {

src/module.c

@@ -7305,7 +7305,7 @@ void ModuleForkDoneHandler(int exitcode, int bysignal) {
  *
  *      RedisModuleEvent_SwapDB
  *
- *          This event is called when a swap db command has been successfully 
+ *          This event is called when a SWAPDB command has been successfully
  *          Executed. 
  *          For this event call currently there is no subevents available.
  *
@@ -7315,6 +7315,18 @@ void ModuleForkDoneHandler(int exitcode, int bysignal) {
  *             int32_t dbnum_first;    // Swap Db first dbnum 
  *             int32_t dbnum_second;   // Swap Db second dbnum 
  *
+ *      RedisModuleEvent_ReplBackup
+ *
+ *          Called when diskless-repl-load config is set to swapdb,
+ *          And redis needs to backup the the current database for the
+ *          possibility to be restored later. A module with global data and
+ *          maybe with aux_load and aux_save callbacks may need to use this
+ *          notification to backup / restore / discard its globals.
+ *          The following sub events are available:
+ *
+ *              REDISMODULE_SUBEVENT_REPL_BACKUP_CREATE
+ *              REDISMODULE_SUBEVENT_REPL_BACKUP_RESTORE
+ *              REDISMODULE_SUBEVENT_REPL_BACKUP_DISCARD
  *
  *
  * The function returns REDISMODULE_OK if the module was successfully subscribed
@@ -7387,6 +7399,8 @@ int RM_IsSubEventSupported(RedisModuleEvent event, int64_t subevent) {
         return subevent < _REDISMODULE_SUBEVENT_LOADING_PROGRESS_NEXT;
     case REDISMODULE_EVENT_SWAPDB:
         return subevent < _REDISMODULE_SUBEVENT_SWAPDB_NEXT;
+    case REDISMODULE_EVENT_REPL_BACKUP:
+        return subevent < _REDISMODULE_SUBEVENT_REPL_BACKUP_NEXT;
     default:
         break;
     }

src/redismodule.h

@@ -215,9 +215,10 @@ typedef uint64_t RedisModuleTimerID;
 #define REDISMODULE_EVENT_MODULE_CHANGE 9
 #define REDISMODULE_EVENT_LOADING_PROGRESS 10
 #define REDISMODULE_EVENT_SWAPDB 11
+#define REDISMODULE_EVENT_REPL_BACKUP 12
 
 /* Next event flag, should be updated if a new event added. */
-#define _REDISMODULE_EVENT_NEXT 12
+#define _REDISMODULE_EVENT_NEXT 13
 
 typedef struct RedisModuleEvent {
     uint64_t id;        /* REDISMODULE_EVENT_... defines. */
@@ -275,6 +276,10 @@ static const RedisModuleEvent
     RedisModuleEvent_SwapDB = {
         REDISMODULE_EVENT_SWAPDB,
         1
+    },
+    RedisModuleEvent_ReplBackup = {
+        REDISMODULE_EVENT_REPL_BACKUP,
+        1
     };
 
 /* Those are values that are used for the 'subevent' callback argument. */
@@ -316,11 +321,15 @@ static const RedisModuleEvent
 #define REDISMODULE_SUBEVENT_MODULE_UNLOADED 1
 #define _REDISMODULE_SUBEVENT_MODULE_NEXT 2
 
-
 #define REDISMODULE_SUBEVENT_LOADING_PROGRESS_RDB 0
 #define REDISMODULE_SUBEVENT_LOADING_PROGRESS_AOF 1
 #define _REDISMODULE_SUBEVENT_LOADING_PROGRESS_NEXT 2
 
+#define REDISMODULE_SUBEVENT_REPL_BACKUP_CREATE 0
+#define REDISMODULE_SUBEVENT_REPL_BACKUP_RESTORE 1
+#define REDISMODULE_SUBEVENT_REPL_BACKUP_DISCARD 2
+#define _REDISMODULE_SUBEVENT_REPL_BACKUP_NEXT 3
+
 #define _REDISMODULE_SUBEVENT_SHUTDOWN_NEXT 0
 #define _REDISMODULE_SUBEVENT_CRON_LOOP_NEXT 0
 #define _REDISMODULE_SUBEVENT_SWAPDB_NEXT 0

tests/modules/testrdb.c

@@ -13,6 +13,45 @@ RedisModuleType *testrdb_type = NULL;
 RedisModuleString *before_str = NULL;
 RedisModuleString *after_str = NULL;
 
+void replBackupCallback(RedisModuleCtx *ctx, RedisModuleEvent e, uint64_t sub, void *data)
+{
+    REDISMODULE_NOT_USED(e);
+    REDISMODULE_NOT_USED(data);
+    static RedisModuleString *before_str_backup = NULL;
+    static RedisModuleString *after_str_backup = NULL;
+
+    switch (sub) {
+    case REDISMODULE_SUBEVENT_REPL_BACKUP_CREATE:
+        assert(before_str_backup == NULL);
+        assert(after_str_backup == NULL);
+        before_str_backup = before_str;
+        after_str_backup = after_str;
+        before_str = NULL;
+        after_str = NULL;
+        break;
+    case REDISMODULE_SUBEVENT_REPL_BACKUP_RESTORE:
+        if (before_str)
+            RedisModule_FreeString(ctx, before_str);
+        if (after_str)
+            RedisModule_FreeString(ctx, after_str);
+        before_str = before_str_backup;
+        after_str = after_str_backup;
+        before_str_backup = NULL;
+        after_str_backup = NULL;
+        break;
+    case REDISMODULE_SUBEVENT_REPL_BACKUP_DISCARD:
+        if (before_str_backup)
+            RedisModule_FreeString(ctx, before_str_backup);
+        if (after_str_backup)
+            RedisModule_FreeString(ctx, after_str_backup);
+        before_str_backup = NULL;
+        after_str_backup = NULL;
+        break;
+    default:
+        assert(0);
+    }
+}
+
 void *testrdb_type_load(RedisModuleIO *rdb, int encver) {
     int count = RedisModule_LoadSigned(rdb);
     RedisModuleString *str = RedisModule_LoadString(rdb);
@@ -247,6 +286,9 @@ int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
     if (RedisModule_CreateCommand(ctx,"testrdb.get.key", testrdb_get_key,"",1,1,1) == REDISMODULE_ERR)
         return REDISMODULE_ERR;
 
+    RedisModule_SubscribeToServerEvent(ctx,
+        RedisModuleEvent_ReplBackup, replBackupCallback);
+
     return REDISMODULE_OK;
 }