Keep FastCGI available during restarts

src/linux_fastcgi.cpp

@@ -699,15 +699,7 @@ volatile bool termination_signal_received = false;
 
 void on_terminate(int sig)
 {
-	if(termination_signal_received)
-		return;
 	termination_signal_received = true;
-	if(getpid() != parent_pid)
-		exit(1);
-	printf("Terminating... PID %i:%i\n", getpid(), parent_pid);
-	wasm_backend_shutdown();
-	server.shutdown();
-	exit(1);
 }
 
 void clear_shared_unit_cache(ServerState& state)
@@ -1069,7 +1061,7 @@ void run_ws_broker()
 		ws_broker.listen(server_state.config["WS_BROKER_SOCKET_PATH"]);
 		chmod(server_state.config["WS_BROKER_SOCKET_PATH"].c_str(), S_IRWXU | S_IRGRP | S_IWGRP);
 	}
-	for(;;)
+	while(!termination_signal_received)
 	{
 		ws_broker.process(50);
 		ws_broker_drain_outbound(ws_broker_outbound_timeout_seconds);
@@ -1254,7 +1246,7 @@ void run_proactive_compiler()
 	}
 	next_scan_at = time_precise();
 
-	for(;;)
+	while(!termination_signal_received)
 	{
 		try
 		{
@@ -1397,10 +1389,21 @@ void listen_for_connections()
 		printf("(P) wasm worker ready: PID %i in %.3f ms\n", getpid(), wasm_ms);
 	else
 		fprintf(stderr, "(!) wasm worker initialization failed: PID %i in %.3f ms: %s\n", getpid(), wasm_ms, wasm_error.c_str());
-	for(;;)
+	while(!termination_signal_received)
 	{
 		server.process(-1);
 	}
+	close_inherited_server_sockets();
+	f64 drain_deadline = time_precise() + (f64)to_u64(server_state.config["WORKER_DRAIN_TIMEOUT_SECONDS"], 10);
+	while(!server.client_sockets.empty() && time_precise() < drain_deadline)
+		server.process(100);
+	if(!server.client_sockets.empty())
+		fprintf(stderr, "(!) worker PID %i drain deadline reached with %zu client connections\n",
+			getpid(), server.client_sockets.size());
+	else
+		printf("(P) worker PID %i drained cleanly\n", getpid());
+	wasm_backend_shutdown();
+	exit(server.client_sockets.empty() ? 0 : 1);
 }
 
 mode_t configured_socket_mode(String value, mode_t fallback)
@@ -1424,6 +1427,25 @@ void chmod_configured_socket(String path, String mode_value, mode_t fallback)
 		fprintf(stderr, "(!) Could not chmod socket %s to %04o: %s\n", path.c_str(), (unsigned int)mode, strerror(errno));
 }
 
+int systemd_fastcgi_listener()
+{
+	const char* listen_pid = getenv("LISTEN_PID");
+	const char* listen_fds = getenv("LISTEN_FDS");
+	if(!listen_pid || !listen_fds)
+		return(-1);
+	if(to_u64(listen_pid, 0) != (u64)getpid())
+		return(-1);
+	if(to_u64(listen_fds, 0) != 1)
+		throw std::runtime_error("UCE requires exactly one systemd FastCGI listener");
+	const char* names = getenv("LISTEN_FDNAMES");
+	if(names && names[0] != '\0' && String(names) != "fastcgi")
+		throw std::runtime_error("systemd listener must be named fastcgi");
+	unsetenv("LISTEN_PID");
+	unsetenv("LISTEN_FDS");
+	unsetenv("LISTEN_FDNAMES");
+	return(3);
+}
+
 StringMap redacted_server_config_for_log(const StringMap& config)
 {
 	StringMap redacted = config;
@@ -1443,13 +1465,16 @@ void init_base_process()
 	server_state.config = make_server_settings();
 	server_state.config["COMPILER_SYS_PATH"] = cwd_get();
 	printf("Compiler base path: %s\n", server_state.config["COMPILER_SYS_PATH"].c_str());
+	int inherited_fastcgi = systemd_fastcgi_listener();
+	if(inherited_fastcgi >= 0)
+		server.adopt_listener(inherited_fastcgi, 'F');
 
 	if(server_state.config["FCGI_PORT"] != "")
 		server.listen(int_val(server_state.config["FCGI_PORT"]));
 
 	printf("%s\n", var_dump(redacted_server_config_for_log(server_state.config)).c_str());
 
-	if(server_state.config["FCGI_SOCKET_PATH"] != "")
+	if(inherited_fastcgi < 0 && server_state.config["FCGI_SOCKET_PATH"] != "")
 	{
 		server.listen(server_state.config["FCGI_SOCKET_PATH"]);
 		chmod_configured_socket(server_state.config["FCGI_SOCKET_PATH"], server_state.config["FCGI_SOCKET_MODE"], 0666);
@@ -1469,7 +1494,9 @@ void init_base_process()
 	mkdir(server_state.config["SESSION_PATH"]);
 
 	signal(SIGCHLD, on_child_exit);
+	signal(SIGTERM, on_terminate);
 	signal(SIGINT, on_terminate);
+	signal(SIGHUP, on_terminate);
 	signal(SIGPIPE, SIG_IGN);
 	srand(time());
 }
@@ -1489,7 +1516,7 @@ int main(int argc, char** argv)
 	ensure_proactive_compiler();
 	ensure_ws_broker();
 
-	for(;;)
+	while(!termination_signal_received)
 	{
 		if(!proactive_compiler_alive())
 			proactive_compiler_pid = 0;
@@ -1512,5 +1539,22 @@ int main(int argc, char** argv)
 		sleep(1);
 	}
 
+	printf("(P) draining %zu workers before shutdown\n", workers.size());
+	for(auto& worker : workers)
+		kill(worker.first, SIGTERM);
+	if(proactive_compiler_pid > 0)
+		kill(proactive_compiler_pid, SIGTERM);
+	if(ws_broker_pid > 0)
+		kill(ws_broker_pid, SIGTERM);
+	f64 drain_deadline = time_precise() + (f64)to_u64(server_state.config["WORKER_DRAIN_TIMEOUT_SECONDS"], 10);
+	while(!workers.empty() && time_precise() < drain_deadline)
+	{
+		on_child_exit(0);
+		usleep(10000);
+	}
+	for(auto& worker : workers)
+		kill(worker.first, SIGKILL);
+	server.shutdown();
+
 	return 0;
 }