This PR extends the module API to support the addition of different
scripting engines to execute 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.
This PR also adds an example of a dummy scripting engine module, to show
how to use the new module API. The dummy module is implemented in
`tests/modules/helloscripting.c`.
The current module API support, only allows to load scripting engines to
run functions using `FCALL` command.
The additions to the module API are the following:
```c
/* This struct represents a scripting engine function that results from the
* compilation of a script by the engine implementation. */
struct ValkeyModuleScriptingEngineCompiledFunction
typedef ValkeyModuleScriptingEngineCompiledFunction **(*ValkeyModuleScriptingEngineCreateFunctionsLibraryFunc)(
ValkeyModuleScriptingEngineCtx *engine_ctx,
const char *code,
size_t timeout,
size_t *out_num_compiled_functions,
char **err);
typedef void (*ValkeyModuleScriptingEngineCallFunctionFunc)(
ValkeyModuleCtx *module_ctx,
ValkeyModuleScriptingEngineCtx *engine_ctx,
ValkeyModuleScriptingEngineFunctionCtx *func_ctx,
void *compiled_function,
ValkeyModuleString **keys,
size_t nkeys,
ValkeyModuleString **args,
size_t nargs);
typedef size_t (*ValkeyModuleScriptingEngineGetUsedMemoryFunc)(
ValkeyModuleScriptingEngineCtx *engine_ctx);
typedef size_t (*ValkeyModuleScriptingEngineGetFunctionMemoryOverheadFunc)(
void *compiled_function);
typedef size_t (*ValkeyModuleScriptingEngineGetEngineMemoryOverheadFunc)(
ValkeyModuleScriptingEngineCtx *engine_ctx);
typedef void (*ValkeyModuleScriptingEngineFreeFunctionFunc)(
ValkeyModuleScriptingEngineCtx *engine_ctx,
void *compiled_function);
/* This struct stores the callback functions implemented by the scripting
* engine to provide the functionality for the `FUNCTION *` commands. */
typedef struct ValkeyModuleScriptingEngineMethodsV1 {
uint64_t version; /* Version of this structure for ABI compat. */
/* Library create function callback. When a new script is loaded, this
* callback will be called with the script code, and returns a list of
* ValkeyModuleScriptingEngineCompiledFunc objects. */
ValkeyModuleScriptingEngineCreateFunctionsLibraryFunc create_functions_library;
/* The callback function called when `FCALL` command is called on a function
* registered in this engine. */
ValkeyModuleScriptingEngineCallFunctionFunc call_function;
/* Function callback to get current used memory by the engine. */
ValkeyModuleScriptingEngineGetUsedMemoryFunc get_used_memory;
/* Function callback to return memory overhead for a given function. */
ValkeyModuleScriptingEngineGetFunctionMemoryOverheadFunc get_function_memory_overhead;
/* Function callback to return memory overhead of the engine. */
ValkeyModuleScriptingEngineGetEngineMemoryOverheadFunc get_engine_memory_overhead;
/* Function callback to free the memory of a registered engine function. */
ValkeyModuleScriptingEngineFreeFunctionFunc free_function;
} ValkeyModuleScriptingEngineMethodsV1;
/* Registers a new scripting engine in the server.
*
* - `engine_name`: the name of the scripting engine. This name will match
* against the engine name specified in the script header using a shebang.
*
* - `engine_ctx`: engine specific context pointer.
*
* - `engine_methods`: the struct with the scripting engine callback functions
* pointers.
*/
int ValkeyModule_RegisterScriptingEngine(ValkeyModuleCtx *ctx,
const char *engine_name,
void *engine_ctx,
ValkeyModuleScriptingEngineMethods engine_methods);
/* Removes the scripting engine from the server.
*
* `engine_name` is the name of the scripting engine.
*
*/
int ValkeyModule_UnregisterScriptingEngine(ValkeyModuleCtx *ctx, const char *engine_name);
```
---------
Signed-off-by: Ricardo Dias <ricardo.dias@percona.com>
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