[tarantool-patches] [PATCH v3 2/3] box: implement on_shutdown triggers

[Serge Petrenko <sergepetrenko@tarantool.org>]

From: Konstantin Osipov <kostja@tarantool.org>

@sergepetrenko:
Instead of running on_shutdown trigggers in box_free() execute them in a
fiber which breaks event loop before the break.
In tarantool_free() move box_free() back after coio_shutdown().
Otherwise tarantool hangs on shutdown occasionally.

Part of #1607
---
 src/box/box.cc |  8 ++++++++
 src/box/box.h  | 11 +++++++++++
 src/main.cc    | 16 ++++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/src/box/box.cc b/src/box/box.cc
index 9642364f6..72119eca1 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -79,6 +79,8 @@ static char status[64] = "unknown";
 /** box.stat rmean */
 struct rmean *rmean_box;
 
+struct rlist on_shutdown = RLIST_HEAD_INITIALIZER(on_shutdown);
+
 static void title(const char *new_status)
 {
 	snprintf(status, sizeof(status), "%s", new_status);
@@ -1671,6 +1673,12 @@ box_set_replicaset_uuid(const struct tt_uuid *replicaset_uuid)
 		diag_raise();
 }
 
+void
+box_run_on_shutdown_triggers(void)
+{
+	trigger_run(&on_shutdown, NULL);
+}
+
 void
 box_free(void)
 {
diff --git a/src/box/box.h b/src/box/box.h
index cb9a512be..e9c14e5cf 100644
--- a/src/box/box.h
+++ b/src/box/box.h
@@ -64,6 +64,11 @@ struct vclock;
  */
 extern const struct vclock *box_vclock;
 
+struct trigger;
+
+/** Invoked on box shutdown. */
+extern struct rlist on_shutdown;
+
 /*
  * Initialize box library
  * @throws C++ exception
@@ -84,6 +89,12 @@ box_free(void);
 void
 box_shutdown_wal(void);
 
+/**
+ * Run on_shutdown triggers.
+ */
+void
+box_run_on_shutdown_triggers(void);
+
 /**
  * Load configuration for box library.
  * Panics on error.
diff --git a/src/main.cc b/src/main.cc
index 2240c564a..8bcc785d5 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -124,6 +124,11 @@ static int
 on_exit_f(va_list ap)
 {
 	(void) ap;
+	/*
+	 * run on_shutdown triggers before event loop break,
+	 * so that we are able to yield in them.
+	 */
+	box_run_on_shutdown_triggers();
 	/* Terminate the main event loop. */
 	ev_break(loop(), EVBREAK_ALL);
 	return 0;
@@ -132,6 +137,17 @@ on_exit_f(va_list ap)
 void
 tarantool_exit(void)
 {
+	static volatile sig_atomic_t num_calls = 0;
+	/*
+	 * We are already running on_shutdown triggers,
+	 * and will exit as soon as they'll finish.
+	 * Do not execute them twice.
+	 */
+	if (num_calls > 0)
+		return;
+
+	++num_calls;
+
 	struct fiber *f = fiber_new("on_shutdown", on_exit_f);
 	if (f == NULL) {
 		say_warn("failed to allocate a fiber to run shutdown routines.");
-- 
2.17.2 (Apple Git-113)