MXS-1570: Test failover with no good candidate

- 1 master, 3 slaves
- "stop slave" on server 2
- "disable" log-bin on server 3
- set multi-source replication on server 4
- take down master
- no slave should be promoted

maxscale-system-test/mysqlmon_failover_no_slaves.cpp

@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2020-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include "testconnections.h"
+#include "fail_switch_rejoin_common.cpp"
+
+int main(int argc, char** argv)
+{
+    interactive = strcmp(argv[argc - 1], "interactive") == 0;
+    Mariadb_nodes::require_gtid(true);
+    TestConnections test(argc, argv);
+
+    delete_slave_binlogs(test);
+    basic_test(test);
+    MYSQL* conn = test.maxscales->open_rwsplit_connection(0);
+    if (!generate_traffic_and_check(test, conn, 5))
+    {
+        return test.global_result;
+    }
+
+    // Make all three slaves ineligible for promotion in different ways.
+    test.repl->connect();
+    MYSQL** nodes = test.repl->nodes;
+    // Slave 1. Just stop slave.
+    test.try_query(nodes[1], "STOP SLAVE;");
+    // Slave 2. Disable binlog.
+    test.repl->stop_node(2);
+    test.repl->stash_server_settings(2);
+    test.repl->disable_server_setting(2, "log-bin");
+    test.repl->start_node(2, (char *) "");
+    // Slave 3. Create a second slave connection to a non-existing server.
+    const char CHANGE_CMD[] = "CHANGE MASTER 'dummy' TO MASTER_HOST = 'imagination_host.img', "
+    "MASTER_PORT = 1234, MASTER_USE_GTID = current_pos, MASTER_USER='repl', MASTER_PASSWORD='repl';";
+    test.try_query(nodes[3], CHANGE_CMD);
+    test.try_query(nodes[3], "START SLAVE;");
+
+    sleep(4);
+    get_output(test);
+
+    test.tprintf(LINE);
+    test.tprintf("Stopping master. Failover should not happen.");
+    test.repl->block_node(0);
+    sleep(10);
+    get_output(test);
+    int master_id = get_master_server_id(test);
+    test.assert(master_id == -1, "Master was promoted even when no slave was eligible.");
+
+    test.repl->unblock_node(0);
+    sleep(1);
+
+    // Restore normal settings.
+    test.try_query(nodes[1], "START SLAVE;");
+    test.repl->stop_node(2);
+    test.repl->restore_server_settings(2);
+    test.repl->start_node(2, (char *) "");
+    test.try_query(nodes[3], "STOP SLAVE 'dummy';");
+    test.try_query(nodes[3], "RESET SLAVE 'dummy' ALL;");
+    test.repl->fix_replication();
+    return test.global_result;
+}