Avoid diskelss-load if modules did not declare they handle read errors

src/module.c

@@ -51,6 +51,7 @@ struct RedisModule {
     list *using;    /* List of modules we use some APIs of. */
     list *filters;  /* List of filters the module has registered. */
     int in_call;    /* RM_Call() nesting level */
+    int options;    /* Moduile options and capabilities. */
 };
 typedef struct RedisModule RedisModule;
 
@@ -771,6 +772,19 @@ long long RM_Milliseconds(void) {
     return mstime();
 }
 
+/* Set flags defining capabilities or behavior bit flags.
+ *
+ * REDISMODULE_OPTIONS_HANDLE_IO_ERRORS:
+ * Generally, modules don't need to bother with this, as the process will just
+ * terminate if a read error happens, however, setting this flag would allow
+ * repl-diskless-load to work if enabled.
+ * The module should use RedisModule_IsIOError after reads, before using the
+ * data that was read, and in case of error, propagate it upwards, and also be
+ * able to release the partially populated value and all it's allocations. */
+void RM_SetModuleOptions(RedisModuleCtx *ctx, int options) {
+    ctx->module->options = options;
+}
+
 /* --------------------------------------------------------------------------
  * Automatic memory management for modules
  * -------------------------------------------------------------------------- */
@@ -3143,7 +3157,7 @@ void *RM_ModuleTypeGetValue(RedisModuleKey *key) {
  * modules this cannot be recovered, but if the module declared capability
  * to handle errors, we'll raise a flag rather than exiting. */
 void moduleRDBLoadError(RedisModuleIO *io) {
-    if (io->flags & REDISMODULE_HANDLE_IO_ERRORS) {
+    if (io->ctx->module->options & REDISMODULE_OPTIONS_HANDLE_IO_ERRORS) {
         io->error = 1;
         return;
     }
@@ -3157,19 +3171,29 @@ void moduleRDBLoadError(RedisModuleIO *io) {
     exit(1);
 }
 
-/* Set flags defining capabilities or behavior */
-void RM_SetIOFlags(RedisModuleIO *io, int flags) {
-    io->flags = flags;
-}
+/* Returns 0 if there's at least one registered data type that did not declare
+ * REDISMODULE_OPTIONS_HANDLE_IO_ERRORS, in which case diskless loading should
+ * be avoided since it could cause data loss. */
+int moduleAllDatatypesHandleErrors() {
+    dictIterator *di = dictGetIterator(modules);
+    dictEntry *de;
 
-/* Get flags which were set by RedisModule_SetIOFlags */
-int RM_GetIOFlags(RedisModuleIO *io) {
-    return io->flags;
+    while ((de = dictNext(di)) != NULL) {
+        struct RedisModule *module = dictGetVal(de);
+        if (listLength(module->types) &&
+            !(module->options & REDISMODULE_OPTIONS_HANDLE_IO_ERRORS))
+        {
+            dictReleaseIterator(di);
+            return 0;
+        }
+    }
+    dictReleaseIterator(di);
+    return 1;
 }
 
 /* Returns true if any previous IO API failed.
- * for Load* APIs the REDISMODULE_HANDLE_IO_ERRORS flag must be set with
- * RediModule_SetIOFlags first. */
+ * for Load* APIs the REDISMODULE_OPTIONS_HANDLE_IO_ERRORS flag must be set with
+ * RediModule_SetModuleOptions first. */
 int RM_IsIOError(RedisModuleIO *io) {
     return io->error;
 }
@@ -5434,9 +5458,8 @@ void moduleRegisterCoreAPI(void) {
     REGISTER_API(ModuleTypeSetValue);
     REGISTER_API(ModuleTypeGetType);
     REGISTER_API(ModuleTypeGetValue);
-    REGISTER_API(GetIOFlags);
-    REGISTER_API(SetIOFlags);
     REGISTER_API(IsIOError);
+    REGISTER_API(SetModuleOptions);
     REGISTER_API(SaveUnsigned);
     REGISTER_API(LoadUnsigned);
     REGISTER_API(SaveSigned);

src/redismodule.h

@@ -140,8 +140,8 @@ typedef uint64_t RedisModuleTimerID;
 /* Do filter RedisModule_Call() commands initiated by module itself. */
 #define REDISMODULE_CMDFILTER_NOSELF    (1<<0)
 
-/* Declare that the module can handle errors with RedisModule_SetIOFlags */
-#define REDISMODULE_HANDLE_IO_ERRORS    (1<<0)
+/* Declare that the module can handle errors with RedisModule_SetModuleOptions. */
+#define REDISMODULE_OPTIONS_HANDLE_IO_ERRORS    (1<<0)
 
 /* ------------------------- End of common defines ------------------------ */
 
@@ -274,9 +274,8 @@ RedisModuleType *REDISMODULE_API_FUNC(RedisModule_CreateDataType)(RedisModuleCtx
 int REDISMODULE_API_FUNC(RedisModule_ModuleTypeSetValue)(RedisModuleKey *key, RedisModuleType *mt, void *value);
 RedisModuleType *REDISMODULE_API_FUNC(RedisModule_ModuleTypeGetType)(RedisModuleKey *key);
 void *REDISMODULE_API_FUNC(RedisModule_ModuleTypeGetValue)(RedisModuleKey *key);
-void REDISMODULE_API_FUNC(RedisModule_SetIOFlags)(RedisModuleIO *io, int flags);
-int REDISMODULE_API_FUNC(RedisModule_GetIOFlags)(RedisModuleIO *io);
 int REDISMODULE_API_FUNC(RedisModule_IsIOError)(RedisModuleIO *io);
+void REDISMODULE_API_FUNC(RedisModule_SetModuleOptions)(RedisModuleCtx *ctx, int options);
 void REDISMODULE_API_FUNC(RedisModule_SaveUnsigned)(RedisModuleIO *io, uint64_t value);
 uint64_t REDISMODULE_API_FUNC(RedisModule_LoadUnsigned)(RedisModuleIO *io);
 void REDISMODULE_API_FUNC(RedisModule_SaveSigned)(RedisModuleIO *io, int64_t value);
@@ -450,9 +449,8 @@ static int RedisModule_Init(RedisModuleCtx *ctx, const char *name, int ver, int
     REDISMODULE_GET_API(ModuleTypeSetValue);
     REDISMODULE_GET_API(ModuleTypeGetType);
     REDISMODULE_GET_API(ModuleTypeGetValue);
-    REDISMODULE_GET_API(SetIOFlags);
-    REDISMODULE_GET_API(GetIOFlags);
     REDISMODULE_GET_API(IsIOError);
+    REDISMODULE_GET_API(SetModuleOptions);
     REDISMODULE_GET_API(SaveUnsigned);
     REDISMODULE_GET_API(LoadUnsigned);
     REDISMODULE_GET_API(SaveSigned);

src/replication.c

@@ -1115,8 +1115,12 @@ void restartAOFAfterSYNC() {
 
 static int useDisklessLoad() {
     /* compute boolean decision to use diskless load */
-    return server.repl_diskless_load == REPL_DISKLESS_LOAD_SWAPDB ||
+    int enabled = server.repl_diskless_load == REPL_DISKLESS_LOAD_SWAPDB ||
            (server.repl_diskless_load == REPL_DISKLESS_LOAD_WHEN_DB_EMPTY && dbTotalServerKeyCount()==0);
+    /* Check all modules handle read errors, otherwise it's not safe to use diskless load. */
+    if (enabled && !moduleAllDatatypesHandleErrors())
+        enabled = 0;
+    return enabled;
 }
 
 /* Helper function for readSyncBulkPayload() to make backups of the current

src/server.h

@@ -599,7 +599,6 @@ typedef struct RedisModuleIO {
                          * 2 (current version with opcodes annotation). */
     struct RedisModuleCtx *ctx; /* Optional context, see RM_GetContextFromIO()*/
     struct redisObject *key;    /* Optional name of key processed */
-    int flags;          /* flags declaring capabilities or behavior */
 } RedisModuleIO;
 
 /* Macro to initialize an IO context. Note that the 'ver' field is populated
@@ -612,7 +611,6 @@ typedef struct RedisModuleIO {
     iovar.ver = 0; \
     iovar.key = keyptr; \
     iovar.ctx = NULL; \
-    iovar.flags = 0; \
 } while(0);
 
 /* This is a structure used to export DEBUG DIGEST capabilities to Redis
@@ -1530,6 +1528,7 @@ void moduleAcquireGIL(void);
 void moduleReleaseGIL(void);
 void moduleNotifyKeyspaceEvent(int type, const char *event, robj *key, int dbid);
 void moduleCallCommandFilters(client *c);
+int moduleAllDatatypesHandleErrors();
 
 /* Utils */
 long long ustime(void);