[Tarantool-patches] [PATCH v20 6/7] box: implement box.lib module

[Cyrill Gorcunov]

Currently to run "C" function from some external module one
have to register it first in "_func" system space. This is
a problem if node is in read-only mode (replica).

Still people would like to have a way to run such functions
even in ro mode. For this sake we implement "box.lib" lua module.

Unlike `box.schema.func` interface the `box.lib` does not defer module
loading procedure until first call of a function. Instead a module
is loaded immediately and if some error happens (say shared
library is corrupted or not found) it pops up early.

The need of use stored C procedures implies that application is
running under serious loads most likely there is modular structure
present on Lua level (ie same shared library is loaded in different
sources) thus we cache the loaded library and reuse it on next
load attempts. To verify that cached library is up to day the
module_cache engine test for file attributes (device, inode, size,
modification time) on every load attempt.

Since both `box.schema.func` and `box.lib` are using caching to minimize
module loading procedure the pass-through caching scheme is
implemented:

 - box.lib relies on module_cache engine for caching;
 - box.schema.func does snoop into box.lib hash table when attempt
   to load a new module, if module is present in box.lib hash then
   it simply referenced from there and added into own hash table;
   in case if module is not present then it loaded from the scratch
   and put into both hashes;
 - the module_reload action in box.schema.func invalidates module_cache
   or fill it if entry is not present.

Closes #4642

Signed-off-by: Cyrill Gorcunov <gorcunov at gmail.com>

@TarantoolBot document
Title: box.lib module

Overview
========

`box.lib` module provides a way to create, delete and execute
`C` procedures from shared libraries. Unlike `box.schema.func`
methods the functions created with `box.lib` help are not persistent
and live purely in memory. Once a node get turned off they are
vanished. An initial purpose for them is to execute them on
nodes which are running in read-only mode.

Module functions
================

`require('box.lib').load(path) -> obj | error`
----------------------------------------------

Loads a module from `path` and return an object instance
associate with the module, otherwise an error is thrown.

The `path` should not end up with shared library extension
(such as `.so`), only a file name shall be there.

Possible errors:

- IllegalParams: module path is either not supplied
  or not a string.
- SystemError: unable to open a module due to a system error.
- ClientError: a module does not exist.
- OutOfMemory: unable to allocate a module.

Example:

``` Lua
-- Without error handling
m = require('box.lib').load('path/to/library)

-- With error handling
m, err = pcall(require('box.lib').load, 'path/to/library')
if err ~= nil then
    print(err)
end
```

`module:unload() -> true | error`
---------------------------------

Unloads a module. Returns `true` on success, otherwise an error
is thrown. Once the module is unloaded one can't load new
functions from this module instance.

Possible errors:

- IllegalParams: a module is not supplied.
- IllegalParams: a module is already unloaded.

Example:

``` Lua
m = require('box.lib').load('path/to/library')
--
-- do something with module
--
m:unload()
```

If there are functions from this module referenced somewhere
in other places of Lua code they still can be executed because
the module continue sitting in memory until the last reference
to it is closed.

If the module become a target to the Lua's garbage collector
then unload is called implicitly.

module:load(name) -> obj | error`
---------------------------------

Loads a new function with name `name` from the previously
loaded `module` and return a callable object instance
associated with the function. On failure an error is thrown.

Possible errors:
 - IllegalParams: function name is either not supplied
   or not a string.
 - IllegalParams: attempt to load a function but module
   has been unloaded already.
 - ClientError: no such function in the module.
 - OutOfMemory: unable to allocate a function.

Example:

``` Lua
-- Load a module if not been loaded yet.
m = require('box.lib').load('path/to/library')
-- Load a function with the `foo` name from the module `m`.
func = m:load('foo')
```

In case if there is no need for further loading of other
functions from the same module then the module might be
unloaded immediately.

``` Lua
m = require('box.lib').load('path/to/library')
func = m:load('foo')
m:unload()
```

`function:unload() -> true | error`
-----------------------------------

Unloads a function. Returns `true` on success, otherwise
an error is thrown.

Possible errors:
 - IllegalParams: function name is either not supplied
   or not a string.
 - IllegalParams: the function already unloaded.

Example:

``` Lua
m = require('box.lib').load('path/to/library')
func = m:load('foo')
--
-- do something with function and cleanup then
--
func:unload()
m:unload()
```

If the function become a target to the Lua's garbage collector
then unload is called implicitly.

Executing a loaded function
===========================

Once function is loaded it can be executed as an ordinary Lua call.
Lets consider the following example. We have a `C` function which
takes two numbers and returns their sum.

``` C
int
cfunc_sum(box_function_ctx_t *ctx, const char *args, const char *args_end)
{
	uint32_t arg_count = mp_decode_array(&args);
	if (arg_count != 2) {
		return box_error_set(__FILE__, __LINE__, ER_PROC_C, "%s",
				     "invalid argument count");
	}
	uint64_t a = mp_decode_uint(&args);
	uint64_t b = mp_decode_uint(&args);

	char res[16];
	char *end = mp_encode_uint(res, a + b);
	box_return_mp(ctx, res, end);
	return 0;
}
```

The name of the function is `cfunc_sum` and the function is built into
`cfunc.so` shared library.

First we should load it as

``` Lua
m = require('box.lib').load('cfunc')
cfunc_sum = m:load('cfunc_sum')
```

Once successfully loaded we can execute it. Lets call the
`cfunc_sum` with wrong number of arguments

``` Lua
cfunc_sum()
 | ---
 | - error: invalid argument count
```

We will see the `"invalid argument count"` message in output.
The error message has been set by the `box_error_set` in `C`
code above.

On success the sum of arguments will be printed out.

``` Lua
cfunc_sum(1, 2)
 | ---
 | - 3
```

The functions may return multiple results. For example a trivial
echo function which prints arguments passed in.

``` Lua
cfunc_echo(1,2,3)
 | ---
 | - 1
 | - 2
 | - 3
```

Module and function caches
==========================

Loading a module is relatively slow procedure because operating
system needs to read the library, resolve its symbols and etc.
Thus to speedup this procedure if the module is loaded for a first
time we put it into an internal cache. If module is sitting in
the cache already and new request to load comes in -- we simply
reuse a previous copy. In case if module is updated on a storage
device then on new load attempt we detect that file attributes
(such as device number, inode, size, modification time) get changed
and reload module from the scratch. Note that newly loaded module
does not intersect with previously loaded modules, the continue
operating with code previously read from cache.

Thus if there is a need to update a module then all module instances
should be unloaded (together with functions) and loaded again.

Similar caching technique applied to functions -- only first function
allocation cause symbol resolving, next ones are simply obtained from
a function cache.
---
 src/box/CMakeLists.txt |   1 +
 src/box/lua/box_lib.c  | 590 +++++++++++++++++++++++++++++++++++++++++
 src/box/lua/box_lib.h  |  25 ++
 src/box/lua/init.c     |   2 +
 test/box/misc.result   |   1 +
 5 files changed, 619 insertions(+)
 create mode 100644 src/box/lua/box_lib.c
 create mode 100644 src/box/lua/box_lib.h

diff --git a/src/box/CMakeLists.txt b/src/box/CMakeLists.txt
index cc2e17e94..95c65eb71 100644
--- a/src/box/CMakeLists.txt
+++ b/src/box/CMakeLists.txt
@@ -196,6 +196,7 @@ add_library(box STATIC
     lua/call.c
     lua/cfg.cc
     lua/console.c
+    lua/box_lib.c
     lua/serialize_lua.c
     lua/tuple.c
     lua/slab.c
diff --git a/src/box/lua/box_lib.c b/src/box/lua/box_lib.c
new file mode 100644
index 000000000..ce2ef8902
--- /dev/null
+++ b/src/box/lua/box_lib.c
@@ -0,0 +1,590 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright 2010-2021, Tarantool AUTHORS, please see AUTHORS file.
+ */
+
+#include <unistd.h>
+#include <string.h>
+#include <lua.h>
+
+#include "box/error.h"
+#include "box/port.h"
+
+#include "tt_static.h"
+
+#include "assoc.h"
+#include "box_lib.h"
+#include "diag.h"
+#include "module_cache.h"
+
+#include "lua/utils.h"
+
+/**
+ * Function descriptor.
+ */
+struct box_module_func {
+	/** C function to call. */
+	struct module_func mf;
+	/** Number of references. */
+	int64_t refs;
+	/** Length of functon name in @a key. */
+	size_t sym_len;
+	/** Length of @a key. */
+	size_t len;
+	/** Function hash key. */
+	char key[0];
+};
+
+/** Function name to box_module_func hash. */
+static struct mh_strnptr_t *func_hash = NULL;
+
+/** A type to find a module from an object. */
+static const char *uname_lib = "tt_uname_box_lib";
+
+/** A type to find a function from an object. */
+static const char *uname_func = "tt_uname_box_lib_func";
+
+/** Get data associated with an object. */
+static void *
+get_udata(struct lua_State *L, const char *uname)
+{
+	void **pptr = luaL_testudata(L, 1, uname);
+	return pptr != NULL ? *pptr : NULL;
+}
+
+/** Set data to a new value. */
+static void
+set_udata(struct lua_State *L, const char *uname, void *ptr)
+{
+	void **pptr = luaL_testudata(L, 1, uname);
+	assert(pptr != NULL);
+	*pptr = ptr;
+}
+
+/** Setup a new data and associate it with an object. */
+static void
+new_udata(struct lua_State *L, const char *uname, void *ptr)
+{
+	*(void **)lua_newuserdata(L, sizeof(void *)) = ptr;
+	luaL_getmetatable(L, uname);
+	lua_setmetatable(L, -2);
+}
+
+/**
+ * Helpers for function cache.
+ */
+static void *
+cache_find(const char *str, size_t len)
+{
+	mh_int_t e = mh_strnptr_find_inp(func_hash, str, len);
+	if (e == mh_end(func_hash))
+		return NULL;
+	return mh_strnptr_node(func_hash, e)->val;
+}
+
+static int
+cache_put(struct box_module_func *cf)
+{
+	const struct mh_strnptr_node_t nd = {
+		.str	= cf->key,
+		.len	= cf->len,
+		.hash	= mh_strn_hash(cf->key, cf->len),
+		.val	= cf,
+	};
+	mh_int_t e = mh_strnptr_put(func_hash, &nd, NULL, NULL);
+	if (e == mh_end(func_hash)) {
+		diag_set(OutOfMemory, sizeof(nd), "malloc",
+			 "box.lib: hash node");
+		return -1;
+	}
+	return 0;
+}
+
+static void
+cache_del(struct box_module_func *cf)
+{
+	mh_int_t e = mh_strnptr_find_inp(func_hash, cf->key, cf->len);
+	if (e != mh_end(func_hash))
+		mh_strnptr_del(func_hash, e, NULL);
+}
+
+/**
+ * Load a module.
+ *
+ * This function takes a module path from the caller
+ * stack @a L and returns cached module instance or
+ * creates a new module object.
+ *
+ * Possible errors:
+ *
+ * - IllegalParams: module path is either not supplied
+ *   or not a string.
+ * - SystemError: unable to open a module due to a system error.
+ * - ClientError: a module does not exist.
+ * - OutOfMemory: unable to allocate a module.
+ *
+ * @returns module object on success or throws an error.
+ */
+static int
+lbox_module_load(struct lua_State *L)
+{
+	const char msg_noname[] = "Expects box.lib.load(\'name\') "
+		"but no name passed";
+
+	if (lua_gettop(L) != 1 || !lua_isstring(L, 1)) {
+		diag_set(IllegalParams, msg_noname);
+		return luaT_error(L);
+	}
+
+	size_t name_len;
+	const char *name = lua_tolstring(L, 1, &name_len);
+
+	if (name_len < 1) {
+		diag_set(IllegalParams, msg_noname);
+		return luaT_error(L);
+	}
+
+	struct module *m = module_load(name, name_len);
+	if (m == NULL)
+		return luaT_error(L);
+
+	new_udata(L, uname_lib, m);
+	return 1;
+}
+
+/**
+ * Unload a module.
+ *
+ * Take a module object from the caller stack @a L and unload it.
+ *
+ * Possible errors:
+ *
+ * - IllegalParams: module is not supplied.
+ * - IllegalParams: the module is unloaded.
+ *
+ * @returns true on success or throwns an error.
+ */
+static int
+lbox_module_unload(struct lua_State *L)
+{
+	if (lua_gettop(L) != 1) {
+		diag_set(IllegalParams, "Expects module:unload()");
+		return luaT_error(L);
+	}
+
+	struct module *m = get_udata(L, uname_lib);
+	if (m == NULL) {
+		diag_set(IllegalParams, "The module is unloaded");
+		return luaT_error(L);
+	}
+
+	set_udata(L, uname_lib, NULL);
+	module_unload(m);
+	lua_pushboolean(L, true);
+	return 1;
+}
+
+/** Handle __index request for a module object. */
+static int
+lbox_module_index(struct lua_State *L)
+{
+	lua_getmetatable(L, 1);
+	lua_pushvalue(L, 2);
+	lua_rawget(L, -2);
+	if (!lua_isnil(L, -1))
+		return 1;
+
+	struct module *m = get_udata(L, uname_lib);
+	if (m == NULL) {
+		lua_pushnil(L);
+		return 1;
+	}
+
+	const char *key = lua_tostring(L, 2);
+	if (key == NULL || lua_type(L, 2) != LUA_TSTRING) {
+		diag_set(IllegalParams,
+			 "Bad params, use __index(<key>)");
+		return luaT_error(L);
+	}
+
+	if (strcmp(key, "path") == 0) {
+		lua_pushstring(L, m->package);
+		return 1;
+	}
+
+	/*
+	 * Internal keys for debug only, not API.
+	 */
+	if (strcmp(key, "debug_refs") == 0) {
+		lua_pushnumber(L, m->refs);
+		return 1;
+	} else if (strcmp(key, "debug_ptr") == 0) {
+		const char *s = tt_sprintf("%p", m);
+		lua_pushstring(L, s);
+		return 1;
+	}
+	return 0;
+}
+
+/** Module representation for REPL (console). */
+static int
+lbox_module_serialize(struct lua_State *L)
+{
+	struct module *m = get_udata(L, uname_lib);
+	if (m == NULL) {
+		lua_pushnil(L);
+		return 1;
+	}
+
+	lua_createtable(L, 0, 1);
+	lua_pushstring(L, m->package);
+	lua_setfield(L, -2, "path");
+	return 1;
+}
+
+/** Collect a module. */
+static int
+lbox_module_gc(struct lua_State *L)
+{
+	struct module *m = get_udata(L, uname_lib);
+	if (m != NULL) {
+		set_udata(L, uname_lib, NULL);
+		module_unload(m);
+	}
+	return 0;
+}
+
+/** Increase reference to a function. */
+static void
+box_module_func_ref(struct box_module_func *cf)
+{
+	assert(cf->refs >= 0);
+	++cf->refs;
+}
+
+/** Free function memory. */
+static void
+box_module_func_delete(struct box_module_func *cf)
+{
+	assert(module_func_is_empty(&cf->mf));
+	TRASH(cf);
+	free(cf);
+}
+
+/** Unreference a function and free if last one. */
+static void
+box_module_func_unref(struct box_module_func *cf)
+{
+	assert(cf->refs > 0);
+	if (--cf->refs == 0) {
+		module_func_unload(&cf->mf);
+		cache_del(cf);
+		box_module_func_delete(cf);
+	}
+}
+
+/** Function name from a hash key. */
+static char *
+box_module_func_name(struct box_module_func *cf)
+{
+	return &cf->key[cf->len - cf->sym_len];
+}
+
+/**
+ * Allocate a new function instance and resolve its address.
+ *
+ * @param m a module the function should be loaded from.
+ * @param key function hash key, ie "addr.module.foo".
+ * @param len length of @a key.
+ * @param sym_len function symbol name length, ie 3 for "foo".
+ *
+ * @returns function instance on success, NULL otherwise (diag is set).
+ */
+static struct box_module_func *
+box_module_func_new(struct module *m, const char *key, size_t len, size_t sym_len)
+{
+	size_t size = sizeof(struct box_module_func) + len + 1;
+	struct box_module_func *cf = malloc(size);
+	if (cf == NULL) {
+		diag_set(OutOfMemory, size, "malloc", "cf");
+		return NULL;
+	}
+
+	cf->len = len;
+	cf->sym_len = sym_len;
+	cf->refs = 0;
+
+	module_func_create(&cf->mf);
+	memcpy(cf->key, key, len);
+	cf->key[len] = '\0';
+
+	if (module_func_load(m, box_module_func_name(cf), &cf->mf) != 0) {
+		box_module_func_delete(cf);
+		return NULL;
+	}
+
+	if (cache_put(cf) != 0) {
+		module_func_unload(&cf->mf);
+		box_module_func_delete(cf);
+		return NULL;
+	}
+
+	/*
+	 * Each new function depends on module presence.
+	 * Module will reside even if been unload
+	 * explicitly after the function creation.
+	 */
+	box_module_func_ref(cf);
+	return cf;
+}
+
+/**
+ * Load a function.
+ *
+ * This function takes a function name from the caller
+ * stack @a L and either returns a cached function or
+ * creates a new function object.
+ *
+ * Possible errors:
+ *
+ * - IllegalParams: function name is either not supplied
+ *   or not a string.
+ * - SystemError: unable to open a module due to a system error.
+ * - ClientError: a module does not exist.
+ * - OutOfMemory: unable to allocate a module.
+ *
+ * @returns module object on success or throws an error.
+ */
+static int
+lbox_module_load_func(struct lua_State *L)
+{
+	const char *method = "function = module:load";
+	const char fmt_noname[] = "Expects %s(\'name\') but no name passed";
+
+	if (lua_gettop(L) != 2 || !lua_isstring(L, 2)) {
+		diag_set(IllegalParams, fmt_noname, method);
+		return luaT_error(L);
+	}
+
+	struct module *m = get_udata(L, uname_lib);
+	if (m == NULL) {
+		const char *fmt =
+			"Expects %s(\'name\') but not module object passed";
+		diag_set(IllegalParams, fmt, method);
+		return luaT_error(L);
+	}
+
+	size_t sym_len;
+	const char *sym = lua_tolstring(L, 2, &sym_len);
+
+	if (sym_len < 1) {
+		diag_set(IllegalParams, fmt_noname, method);
+		return luaT_error(L);
+	}
+
+	/*
+	 * Functions are bound to a module symbols, thus
+	 * since the hash is global it should be unique
+	 * per module. The symbol (function name) is the
+	 * last part of the hash key.
+	 */
+	const char *key = tt_sprintf("%p.%s.%s", (void *)m,
+				     m->package, sym);
+	size_t len = strlen(key);
+
+	struct box_module_func *cf = cache_find(key, len);
+	if (cf == NULL) {
+		cf = box_module_func_new(m, key, len, sym_len);
+		if (cf == NULL)
+			return luaT_error(L);
+	} else {
+		box_module_func_ref(cf);
+	}
+
+	new_udata(L, uname_func, cf);
+	return 1;
+}
+
+/**
+ * Unload a function.
+ *
+ * Take a function object from the caller stack @a L and unload it.
+ *
+ * Possible errors:
+ *
+ * - IllegalParams: the function is not supplied.
+ * - IllegalParams: the function already unloaded.
+ *
+ * @returns true on success or throwns an error.
+ */
+static int
+lbox_func_unload(struct lua_State *L)
+{
+	if (lua_gettop(L) != 1) {
+		diag_set(IllegalParams, "Expects function:unload()");
+		return luaT_error(L);
+	}
+
+	struct box_module_func *cf = get_udata(L, uname_func);
+	if (cf == NULL) {
+		diag_set(IllegalParams, "The function is unloaded");
+		return luaT_error(L);
+	}
+
+	set_udata(L, uname_func, NULL);
+	box_module_func_unref(cf);
+
+	lua_pushboolean(L, true);
+	return 1;
+}
+
+/** Handle __index request for a function object. */
+static int
+lbox_func_index(struct lua_State *L)
+{
+	lua_getmetatable(L, 1);
+	lua_pushvalue(L, 2);
+	lua_rawget(L, -2);
+	if (!lua_isnil(L, -1))
+		return 1;
+
+	struct box_module_func *cf = get_udata(L, uname_func);
+	if (cf == NULL) {
+		lua_pushnil(L);
+		return 1;
+	}
+
+	const char *key = lua_tostring(L, 2);
+	if (key == NULL || lua_type(L, 2) != LUA_TSTRING) {
+		diag_set(IllegalParams,
+			 "Bad params, use __index(<key>)");
+		return luaT_error(L);
+	}
+
+	if (strcmp(key, "name") == 0) {
+		lua_pushstring(L, box_module_func_name(cf));
+		return 1;
+	}
+
+	/*
+	 * Internal keys for debug only, not API.
+	 */
+	if (strcmp(key, "debug_refs") == 0) {
+		lua_pushnumber(L, cf->refs);
+		return 1;
+	} else if (strcmp(key, "debug_key") == 0) {
+		lua_pushstring(L, cf->key);
+		return 1;
+	} else if (strcmp(key, "debug_module_ptr") == 0) {
+		const char *s = tt_sprintf("%p", cf->mf.module);
+		lua_pushstring(L, s);
+		return 1;
+	} else if (strcmp(key, "debug_module_refs") == 0) {
+		lua_pushnumber(L, cf->mf.module->refs);
+		return 1;
+	}
+	return 0;
+}
+
+/** Function representation for REPL (console). */
+static int
+lbox_func_serialize(struct lua_State *L)
+{
+	struct box_module_func *cf = get_udata(L, uname_func);
+	if (cf == NULL) {
+		lua_pushnil(L);
+		return 1;
+	}
+
+	lua_createtable(L, 0, 1);
+	lua_pushstring(L, box_module_func_name(cf));
+	lua_setfield(L, -2, "name");
+	return 1;
+}
+
+/** Collect a function. */
+static int
+lbox_func_gc(struct lua_State *L)
+{
+	struct box_module_func *cf = get_udata(L, uname_func);
+	if (cf != NULL) {
+		set_udata(L, uname_func, NULL);
+		box_module_func_unref(cf);
+	}
+	return 0;
+}
+
+
+/** Call a function by its name from the Lua code. */
+static int
+lbox_func_call(struct lua_State *L)
+{
+	struct box_module_func *cf = get_udata(L, uname_func);
+	if (cf == NULL) {
+		diag_set(IllegalParams, "The function is unloaded");
+		return luaT_error(L);
+	}
+
+	lua_State *args_L = luaT_newthread(tarantool_L);
+	if (args_L == NULL)
+		return luaT_error(L);
+
+	int coro_ref = luaL_ref(tarantool_L, LUA_REGISTRYINDEX);
+	lua_xmove(L, args_L, lua_gettop(L) - 1);
+
+	struct port args;
+	port_lua_create(&args, args_L);
+	((struct port_lua *)&args)->ref = coro_ref;
+
+	struct port ret;
+
+	if (module_func_call(&cf->mf, &args, &ret) != 0) {
+		port_destroy(&args);
+		return luaT_error(L);
+	}
+
+	int top = lua_gettop(L);
+	port_dump_lua(&ret, L, true);
+	int cnt = lua_gettop(L) - top;
+
+	port_destroy(&ret);
+	port_destroy(&args);
+
+	return cnt;
+}
+
+void
+box_lua_lib_init(struct lua_State *L)
+{
+	func_hash = mh_strnptr_new();
+	if (func_hash == NULL)
+		panic("box.lib: Can't allocate func hash table");
+
+	static const struct luaL_Reg top_methods[] = {
+		{ "load",		lbox_module_load	},
+		{ NULL, NULL },
+	};
+	luaL_register(L, "box.lib", top_methods);
+	lua_pop(L, 1);
+
+	static const struct luaL_Reg lbox_module_methods[] = {
+		{ "unload",		lbox_module_unload	},
+		{ "load",		lbox_module_load_func	},
+		{ "__index",		lbox_module_index	},
+		{ "__serialize",	lbox_module_serialize	},
+		{ "__gc",		lbox_module_gc		},
+		{ NULL, NULL },
+	};
+	luaL_register_type(L, uname_lib, lbox_module_methods);
+
+	static const struct luaL_Reg lbox_func_methods[] = {
+		{ "unload",		lbox_func_unload	},
+		{ "__index",		lbox_func_index		},
+		{ "__serialize",	lbox_func_serialize	},
+		{ "__gc",		lbox_func_gc		},
+		{ "__call",		lbox_func_call		},
+		{ NULL, NULL },
+	};
+	luaL_register_type(L, uname_func, lbox_func_methods);
+}
diff --git a/src/box/lua/box_lib.h b/src/box/lua/box_lib.h
new file mode 100644
index 000000000..a86691b42
--- /dev/null
+++ b/src/box/lua/box_lib.h
@@ -0,0 +1,25 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright 2010-2021, Tarantool AUTHORS, please see AUTHORS file.
+ */
+
+#pragma once
+
+#if defined(__cplusplus)
+extern "C" {
+#endif /* defined(__cplusplus) */
+
+struct lua_State;
+
+/**
+ * Initialize Lua box.lib.
+ *
+ * @param L Lua state where to register.
+ */
+void
+box_lua_lib_init(struct lua_State *L);
+
+#if defined(__cplusplus)
+}
+#endif /* defined(__plusplus) */
diff --git a/src/box/lua/init.c b/src/box/lua/init.c
index fbcdfb20b..3fb433e7a 100644
--- a/src/box/lua/init.c
+++ b/src/box/lua/init.c
@@ -60,6 +60,7 @@
 #include "box/lua/cfg.h"
 #include "box/lua/xlog.h"
 #include "box/lua/console.h"
+#include "box/lua/box_lib.h"
 #include "box/lua/tuple.h"
 #include "box/lua/execute.h"
 #include "box/lua/key_def.h"
@@ -465,6 +466,7 @@ box_lua_init(struct lua_State *L)
 	box_lua_tuple_init(L);
 	box_lua_call_init(L);
 	box_lua_cfg_init(L);
+	box_lua_lib_init(L);
 	box_lua_slab_init(L);
 	box_lua_index_init(L);
 	box_lua_space_init(L);
diff --git a/test/box/misc.result b/test/box/misc.result
index e18a46e02..59fc60a22 100644
--- a/test/box/misc.result
+++ b/test/box/misc.result
@@ -85,6 +85,7 @@ t
   - info
   - internal
   - is_in_txn
+  - lib
   - on_commit
   - on_rollback
   - once
-- 
2.30.2