tarantool / tarantool / 24079604329

88%

Build Type

push

github

Committed by locker

Commit Message

lua: allow to export IPROTO functions without polluting globals

Before this patch, there were two ways to make a Lua function callable
over IPROTO: (1) add it to the `_func` system space or (2) add it to
the Lua global namespace `_G`. The first way was never popular because
it implies a DDL operation. The second way may result in undesired side
effects because it pollutes the global namespace. This patch introduces
the third way - `box.iproto.export()`. It adds a function to
the internal Lua table `box.internal.func_registry` checked by
`box_lua_find()` before falling back on `_G`.

The clearly-defined registry of all exported functions will let us
implement balancing of `IPROTO_CALL` requests among application threads
at the IPROTO thread level.

Closes #10036
Needed for #12312

@TarantoolBot document
Title: Document `box.iproto.export()`
Since: 3.7

It is now possible to expose a Lua function to `IPROTO_CALL` requests
without polluting the global Lua namespace:

```lua
box.iproto.export('echo', function(...) return ... end)
```

The `IPROTO_CALL` request handler first looks up the function name
among all functions exported with `box.iproto.export()`, then falls
back on searching in `_G` if not found.

`box.iproto.export()` may be called both before and after `box.cfg()`.

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