Bug fix: if process is stopped, refrain from signaling PID 0. (#921)

* Bug fix: if process is stopped, refrain from signaling PID 0.

* Add missing init for the Postgres expected status file.

src/bin/pg_autoctl/cli_drop_node.c

@@ -638,7 +638,7 @@ cli_drop_local_node(KeeperConfig *config, bool dropAndDestroy)
 	 * so we can take over. This can happen either because --force was used
 	 * or because 30 seconds was not enough time for the service to exit.
 	 */
-	if (!stopped)
+	if (!stopped && pid != 0)
 	{
 		/* if the service isn't terminated, signal it to quit now */
 		log_info("Sending signal %s to pg_autoctl process %d",
@@ -670,6 +670,8 @@ cli_drop_local_node(KeeperConfig *config, bool dropAndDestroy)
 	 */
 	bool dropped = false;
 
+	local_postgres_init(&(keeper.postgres), &(config->pgSetup));
+
 	if (keeper_ensure_node_has_been_dropped(&keeper, &dropped) && dropped)
 	{
 		log_info("This node with id %lld in formation \"%s\" and group %d "

src/bin/pg_autoctl/pidfile.c

@@ -499,6 +499,11 @@ pidfile_as_json(JSON_Value *js, const char *pidfile, bool includeStatus)
 }
 
 
+/*
+ * is_process_stopped reads given pidfile and checks if the included PID
+ * belongs to a process that's still running, and if not, sets the *stopped
+ * boolean to true.
+ */
 bool
 is_process_stopped(const char *pidfile, bool *stopped, pid_t *pid)
 {
@@ -520,8 +525,8 @@ is_process_stopped(const char *pidfile, bool *stopped, pid_t *pid)
 
 
 /*
- * wait_for_process_to_stop waits until the PID found in the pidfile is not running
- * anymore.
+ * wait_for_process_to_stop waits until the PID found in the pidfile is not
+ * running anymore.
  */
 bool
 wait_for_process_to_stop(const char *pidfile, int timeout, bool *stopped, pid_t *pid)
@@ -532,6 +537,12 @@ wait_for_process_to_stop(const char *pidfile, int timeout, bool *stopped, pid_t
 		return false;
 	}
 
+	/* if the process has stopped already, we're done here */
+	if (*stopped)
+	{
+		return true;
+	}
+
 	log_info("An instance of pg_autoctl is running with PID %d, "
 			 "waiting for it to stop.", *pid);