[Tarantool-patches] [PATCH v4] lua: fix running init lua script

[Artem Starshov]

When tarantool launched with -e flag and in
script after there is an error, program hangs.
This happens because shed fiber launches separate
fiber for init user script and starts auxiliary
event loop. It's supposed that fiber will stop
this loop, but in case of error in script, fiber
tries to stop a loop when the last one isn't
started yet.

Added a flag, which will watch is loop started and
when fiber tries to call `ev_break()` we can be sure
that loop is running already.

Fixes #4983
---
@ChangeLog: Fixed a hang when tarantool launched with the -e option and users
script throws an error (`tarantool -e 'assert(false)'`) (gh-4983).

Changes in v2:
    - Test commit squashed with code fix commit;
    - Fixed comments in test;
    - Fixed commit message (no stairs);
    - Closes -> Fixes;
    - Removed small bugs in test;
    - Moved test to tap.test(name, func).

Changes in v3:
    - Added more information to change log;
    - 'src/lua` -> 'lua' for patch name;
    - Code-style fixes in test.

Changes in v4:
    - Set timeout for operations like for cond_var wait in test-run
    - Added module `process_timeout` in test/app-tap/lua for further using

Branch: https://github.com/tarantool/tarantool/tree/artemreyt/gh-4983-tnt-e-assert-false-hangs
Issue: https://github.com/tarantool/tarantool/issues/4983

 src/lua/init.c                                |  9 +++
 .../gh-4983-tnt-e-assert-false-hangs.test.lua | 46 +++++++++++++++
 test/app-tap/lua/process_timeout.lua          | 57 +++++++++++++++++++
 test/app-tap/suite.ini                        |  2 +-
 4 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100755 test/app-tap/gh-4983-tnt-e-assert-false-hangs.test.lua
 create mode 100644 test/app-tap/lua/process_timeout.lua

diff --git a/src/lua/init.c b/src/lua/init.c
index a0b2fc775..92bdb82c0 100644
--- a/src/lua/init.c
+++ b/src/lua/init.c
@@ -569,6 +569,7 @@ run_script_f(va_list ap)
 	 * never really dead. It never returns from its function.
 	 */
 	struct diag *diag = va_arg(ap, struct diag *);
+	bool aux_loop_is_run = false;
 
 	/*
 	 * Load libraries and execute chunks passed by -l and -e
@@ -611,6 +612,7 @@ run_script_f(va_list ap)
 	 * loop and re-schedule this fiber.
 	 */
 	fiber_sleep(0.0);
+	aux_loop_is_run = true;
 
 	if (path && strcmp(path, "-") != 0 && access(path, F_OK) == 0) {
 		/* Execute script. */
@@ -650,6 +652,13 @@ run_script_f(va_list ap)
 	 * return control back to tarantool_lua_run_script.
 	 */
 end:
+	/*
+	 * Auxiliary loop in tarantool_lua_run_script
+	 * should start (ev_run()) before this fiber
+	 * invokes ev_break().
+	 */
+	if (!aux_loop_is_run)
+		fiber_sleep(0.0);
 	ev_break(loop(), EVBREAK_ALL);
 	return 0;
 
diff --git a/test/app-tap/gh-4983-tnt-e-assert-false-hangs.test.lua b/test/app-tap/gh-4983-tnt-e-assert-false-hangs.test.lua
new file mode 100755
index 000000000..891a56ade
--- /dev/null
+++ b/test/app-tap/gh-4983-tnt-e-assert-false-hangs.test.lua
@@ -0,0 +1,46 @@
+#!/usr/bin/env tarantool
+
+local common = require('process_timeout')
+local tap = require('tap')
+local fio = require('fio')
+
+--
+-- gh-4983: tarantool -e 'assert(false)' hangs
+--
+
+local TARANTOOL_PATH = arg[-1]
+local output_file = fio.abspath('out.txt')
+local line = ('%s -e "assert(false)" > %s 2>&1 & echo $!'):
+        format(TARANTOOL_PATH, output_file)
+
+-- Like a default timeout for `cond_wait` in test-run
+local process_waiting_timeout = 60.0
+local file_read_timeout = 60.0
+local file_open_timeout = 60.0
+local file_read_interval = 0.2
+
+local res = tap.test('gh-4983-tnt-e-assert-false-hangs', function(test)
+    test:plan(2)
+
+    local pid = tonumber(io.popen(line):read('*line'))
+    assert(pid, 'pid of proccess can\'t be recieved')
+
+    local process_completed = common.wait_process_completion(pid,
+            process_waiting_timeout)
+
+    test:ok(process_completed,
+            ('tarantool process with pid = %d completed'):format(pid))
+
+    -- Kill process if hangs.
+    if not process_completed then ffi.C.kill(pid, 9) end
+
+    local fh = common.open_with_timeout(output_file, file_open_timeout)
+    assert(fh, 'error while opening ' .. output_file)
+
+    local data = common.read_with_timeout(fh, file_read_timeout, file_read_interval)
+    test:like(data, 'assertion failed', 'assertion failure is displayed')
+
+    fh:close()
+end)
+
+os.exit(res and 0 or 1)
diff --git a/test/app-tap/lua/process_timeout.lua b/test/app-tap/lua/process_timeout.lua
new file mode 100644
index 000000000..141fb0e43
--- /dev/null
+++ b/test/app-tap/lua/process_timeout.lua
@@ -0,0 +1,57 @@
+local fiber = require('fiber')
+local clock = require('clock')
+local ffi = require('ffi')
+local fio = require('fio')
+local errno = require('errno')
+
+-- For process_is_alive.
+ffi.cdef([[
+    int kill(pid_t pid, int sig);
+]])
+
+---  Verify whether a process is alive.
+local function process_is_alive(pid)
+    local rc = ffi.C.kill(pid, 0)
+    return rc == 0 or errno() ~= errno.ESRCH
+end
+
+--- Returns true if process completed before timeout, false otherwise.
+local function wait_process_completion(pid, timeout)
+    local start_time = clock.monotonic()
+    local process_completed = false
+    while clock.monotonic() - start_time < timeout do
+        if not process_is_alive(pid) then
+            process_completed = true
+            break
+        end
+    end
+    return process_completed
+end
+
+--- Open file on reading with timeout.
+local function open_with_timeout(filename, timeout)
+    local fh
+    local start_time = clock.monotonic()
+    while not fh and clock.monotonic() - start_time < timeout do
+        fh = fio.open(filename, {'O_RDONLY'})
+    end
+    return fh
+end
+
+--- Try to read from file with timeout with interval.
+local function read_with_timeout(fh, timeout, interval)
+    local data = ''
+    local start_time = clock.monotonic()
+    while #data == 0 and clock.monotonic() - start_time < timeout do
+        data = fh:read()
+        if #data == 0 then fiber.sleep(interval) end
+    end
+    return data
+end
+
+return {
+    process_is_alive = process_is_alive,
+    wait_process_completion = wait_process_completion,
+    open_with_timeout = open_with_timeout,
+    read_with_timeout = read_with_timeout
+}
diff --git a/test/app-tap/suite.ini b/test/app-tap/suite.ini
index 2f16128f9..6e27f88d6 100644
--- a/test/app-tap/suite.ini
+++ b/test/app-tap/suite.ini
@@ -1,7 +1,7 @@
 [default]
 core = app
 description = application server tests (TAP)
-lua_libs = lua/require_mod.lua lua/serializer_test.lua
+lua_libs = lua/require_mod.lua lua/serializer_test.lua lua/process_timeout.lua
 is_parallel = True
 pretest_clean = True
 use_unix_sockets_iproto = True
-- 
2.28.0