Adds support for scripting engines as Valkey modules

This commit extends the module API to support the addition of different
scripting engines to run user defined functions.

The scripting engine can be implemented as a Valkey module, and can be
dynamically loaded with the `loadmodule` config directive, or with
the `MODULE LOAD` command.

The current module API support, only allows to load scripting engines to
run functions using `FCALL` command.

In a follow up PR, we will move the Lua scripting engine implmentation
into its own module.

Signed-off-by: Ricardo Dias <[email protected]>

src/aof.c

@@ -2175,7 +2175,7 @@ static int rewriteFunctions(rio *aof) {
     dictIterator *iter = dictGetIterator(functions);
     dictEntry *entry = NULL;
     while ((entry = dictNext(iter))) {
-        functionLibInfo *li = dictGetVal(entry);
+        ValkeyModuleScriptingEngineFunctionLibrary *li = dictGetVal(entry);
         if (rioWrite(aof, "*3\r\n", 4) == 0) goto werr;
         char function_load[] = "$8\r\nFUNCTION\r\n$4\r\nLOAD\r\n";
         if (rioWrite(aof, function_load, sizeof(function_load) - 1) == 0) goto werr;

src/function_lua.c

@@ -64,7 +64,7 @@ typedef struct luaFunctionCtx {
 } luaFunctionCtx;
 
 typedef struct loadCtx {
-    functionLibInfo *li;
+    ValkeyModuleScriptingEngineFunctionLibrary *li;
     monotime start_time;
     size_t timeout;
 } loadCtx;
@@ -100,7 +100,7 @@ static void luaEngineLoadHook(lua_State *lua, lua_Debug *ar) {
  *
  * Return NULL on compilation error and set the error to the err variable
  */
-static int luaEngineCreate(void *engine_ctx, functionLibInfo *li, sds blob, size_t timeout, sds *err) {
+static int luaEngineCreate(void *engine_ctx, ValkeyModuleScriptingEngineFunctionLibrary *li, const char *blob, size_t timeout, char **err) {
     int ret = C_ERR;
     luaEngineCtx *lua_engine_ctx = engine_ctx;
     lua_State *lua = lua_engine_ctx->lua;
@@ -114,8 +114,8 @@ static int luaEngineCreate(void *engine_ctx, functionLibInfo *li, sds blob, size
     lua_pop(lua, 1);                                   /* pop the metatable */
 
     /* compile the code */
-    if (luaL_loadbuffer(lua, blob, sdslen(blob), "@user_function")) {
-        *err = sdscatprintf(sdsempty(), "Error compiling function: %s", lua_tostring(lua, -1));
+    if (luaL_loadbuffer(lua, blob, strlen(blob), "@user_function")) {
+        *err = valkey_asprintf("Error compiling function: %s", lua_tostring(lua, -1));
         lua_pop(lua, 1); /* pops the error */
         goto done;
     }
@@ -133,7 +133,7 @@ static int luaEngineCreate(void *engine_ctx, functionLibInfo *li, sds blob, size
     if (lua_pcall(lua, 0, 0, 0)) {
         errorInfo err_info = {0};
         luaExtractErrorInformation(lua, &err_info);
-        *err = sdscatprintf(sdsempty(), "Error registering functions: %s", err_info.msg);
+        *err = valkey_asprintf("Error registering functions: %s", err_info.msg);
         lua_pop(lua, 1); /* pops the error */
         luaErrorInformationDiscard(&err_info);
         goto done;
@@ -158,7 +158,7 @@ static int luaEngineCreate(void *engine_ctx, functionLibInfo *li, sds blob, size
 /*
  * Invole the give function with the given keys and args
  */
-static void luaEngineCall(scriptRunCtx *run_ctx,
+static void luaEngineCall(ValkeyModuleScriptingEngineFunctionCallCtx *func_ctx,
                           void *engine_ctx,
                           void *compiled_function,
                           robj **keys,
@@ -177,6 +177,7 @@ static void luaEngineCall(scriptRunCtx *run_ctx,
 
     serverAssert(lua_isfunction(lua, -1));
 
+    scriptRunCtx *run_ctx = moduleGetScriptRunCtxFromFunctionCtx(func_ctx);
     luaCallFunction(run_ctx, lua, keys, nkeys, args, nargs, 0);
     lua_pop(lua, 1); /* Pop error handler */
 }
@@ -406,12 +407,13 @@ static int luaRegisterFunction(lua_State *lua) {
         return luaError(lua);
     }
 
-    sds err = NULL;
+    char *err = NULL;
     if (functionLibCreateFunction(register_f_args.name, register_f_args.lua_f_ctx, load_ctx->li, register_f_args.desc,
                                   register_f_args.f_flags, &err) != C_OK) {
+        serverAssert(err != NULL);
         luaRegisterFunctionArgsDispose(lua, &register_f_args);
         luaPushError(lua, err);
-        sdsfree(err);
+        zfree(err);
         return luaError(lua);
     }
 
@@ -494,16 +496,13 @@ int luaEngineInitEngine(void) {
     lua_enablereadonlytable(lua_engine_ctx->lua, -1, 1); /* protect the new global table */
     lua_replace(lua_engine_ctx->lua, LUA_GLOBALSINDEX);  /* set new global table as the new globals */
 
-
-    engine *lua_engine = zmalloc(sizeof(*lua_engine));
-    *lua_engine = (engine){
-        .engine_ctx = lua_engine_ctx,
-        .create = luaEngineCreate,
-        .call = luaEngineCall,
-        .get_used_memory = luaEngineGetUsedMemoy,
-        .get_function_memory_overhead = luaEngineFunctionMemoryOverhead,
-        .get_engine_memory_overhead = luaEngineMemoryOverhead,
-        .free_function = luaEngineFreeFunction,
-    };
-    return functionsRegisterEngine(LUA_ENGINE_NAME, lua_engine);
+    return functionsRegisterEngine(LUA_ENGINE_NAME,
+                                   NULL,
+                                   lua_engine_ctx,
+                                   luaEngineCreate,
+                                   luaEngineCall,
+                                   luaEngineGetUsedMemoy,
+                                   luaEngineFunctionMemoryOverhead,
+                                   luaEngineMemoryOverhead,
+                                   luaEngineFreeFunction);
 }