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

[Serge Petrenko <sergepetrenko@tarantool.org>]

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.
+ */
+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.result b/test/box/misc.result
index d266bb334..981e20157 100644
--- a/test/box/misc.result
+++ b/test/box/misc.result
@@ -1248,3 +1248,51 @@ 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
+---
+...
+_ = 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})
+---
+- on_shutdown 1
+...
+test_run:grep_log('default', 'on_shutdown 2', nil, {noreset=true})
+---
+- null
+...
+test_run:grep_log('default', 'on_shutdown 3', nil, {noreset=true})
+---
+- on_shutdown 3
+...
+test_run:grep_log('default', 'on_shutdown 4', nil, {noreset=true})
+---
+- on_shutdown 4
+...
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
+_ = 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})
-- 
2.17.2 (Apple Git-113)