Re: [tarantool-patches] [PATCH v3 3/3] box: introduce on_shutdown triggers to lua

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Tue, Dec 11, 2018 at 04:24:40PM +0300, Serge Petrenko wrote:
> Make it possible to register on_shutdown triggers from lua via
> box.ctl.on_shutdown()
> 
> Closes #1607
> 
> @TarantoolBot document
> Title: Document box.ctl.on_shutdown triggers
> on_shutdown triggers may be set similar to space:on_replace triggers:
> ```
> box.ctl.on_shutdown(new_trigger, old_trigger)
> ```
> The triggers will be run when tarantool exits due to receiving one of
> the signals: `SIGTERM`, `SIGINT`, `SIGHUP`.
> 
> Note that the triggers will not be run if you exit tarantool by typing
> `os.exit()` to the lua console or if tarantool receives a fatal signal:
> `SIGSEGV`, `SIGABORT` or any signal causing immediate program
> termination.
> ---
>  src/box/lua/ctl.c      | 21 ++++++++++++++++++
>  test/box/misc.result   | 48 ++++++++++++++++++++++++++++++++++++++++++
>  test/box/misc.test.lua | 19 +++++++++++++++++
>  3 files changed, 88 insertions(+)
> 
> diff --git a/src/box/lua/ctl.c b/src/box/lua/ctl.c
> index 9a105ed5c..aa835d6d5 100644
> --- a/src/box/lua/ctl.c
> +++ b/src/box/lua/ctl.c
> @@ -37,6 +37,7 @@
>  #include <lualib.h>
>  
>  #include "lua/utils.h"
> +#include "lua/trigger.h"
>  
>  #include "box/box.h"
>  
> @@ -64,9 +65,29 @@ lbox_ctl_wait_rw(struct lua_State *L)
>  	return 0;
>  }
>  
> +/*
> + * This is a placeholder.
> + * We may decide to pass some arguments to on_shutdown triggers.

I don't think so. Let's instead remove this placeholder and add a check
for push_event != NULL to lbox_trigger_run().

> + */
> +static int
> +lbox_push_on_shutdown(struct lua_State *L, void *event)
> +{
> +	(void)L;
> +	(void)event;
> +	return 0;
> +}
> +
> +static int
> +lbox_ctl_on_shutdown(struct lua_State *L)
> +{
> +	return lbox_trigger_reset(L, 2, &on_shutdown, lbox_push_on_shutdown,
> +				  NULL);
> +}
> +
>  static const struct luaL_Reg lbox_ctl_lib[] = {
>  	{"wait_ro", lbox_ctl_wait_ro},
>  	{"wait_rw", lbox_ctl_wait_rw},
> +	{"on_shutdown", lbox_ctl_on_shutdown},
>  	{NULL, NULL}
>  };
>  
> diff --git a/test/box/misc.test.lua b/test/box/misc.test.lua
> index cc6cb34fb..f9d0f53f2 100644
> --- a/test/box/misc.test.lua
> +++ b/test/box/misc.test.lua
> @@ -352,3 +352,22 @@ rows == expected_rows
>  lsn == expected_lsn
>  box.cfg{too_long_threshold = too_long_threshold}
>  s:drop()
> +
> +--
> +-- gh-1607: on_shutdown triggers.
> +--
> +f = function() print('on_shutdown 1') end
> +g = function() print('on_shutdown 2') end
> +h = function() print('on_shutdown 3') end
> +-- check that on_shutdown triggers may yield and sleep.
> +fiber = require('fiber')
> +trig = function() fiber.sleep(0.01) fiber.yield() print('on_shutdown 4') end

Let's test something more complicated, e.g. inserting a tuple into
a space.

> +_ = box.ctl.on_shutdown(f)
> +_ = box.ctl.on_shutdown(g)
> +_ = box.ctl.on_shutdown(h, g)
> +_ = box.ctl.on_shutdown(trig)
> +test_run:cmd('restart server default')
> +test_run:grep_log('default', 'on_shutdown 1', nil, {noreset=true})
> +test_run:grep_log('default', 'on_shutdown 2', nil, {noreset=true})
> +test_run:grep_log('default', 'on_shutdown 3', nil, {noreset=true})
> +test_run:grep_log('default', 'on_shutdown 4', nil, {noreset=true})