MXS-1961: Add test case

Added a test case that reproduces the problem.

maxscale-system-test/CMakeLists.txt

@@ -954,6 +954,10 @@ add_test_executable(mxs1949_warn_user_injection.cpp mxs1949_warn_user_injection
 # https://jira.mariadb.org/browse/MXS-1958
 add_test_executable(mxs1958_insert_priv.cpp mxs1958_insert_priv replication LABELS REPL_BACKEND)
 
+# MXS-1961: Standalone master loses master status
+# https://jira.mariadb.org/browse/MXS-1961
+add_test_executable(mxs1961_standalone_rejoin.cpp mxs1961_standalone_rejoin mxs1961_standalone_rejoin LABELS REPL_BACKEND)
+
 configure_file(templates.h.in templates.h @ONLY)
 
 include(CTest)

maxscale-system-test/cnf/maxscale.cnf.template.mxs1961_standalone_rejoin

@@ -0,0 +1,60 @@
+[maxscale]
+threads=###threads###
+
+[MySQL-Monitor]
+type=monitor
+module=mysqlmon
+servers= server1, server2, server3
+user=maxskysql
+passwd= skysql
+monitor_interval=1000
+detect_standalone_master=true
+failcount=1
+allow_cluster_recovery=true
+auto_failover=true
+auto_rejoin=true
+replication_user=repl
+replication_password=repl
+enforce_read_only_slaves=1
+verify_master_failure=false
+
+[RW Split Router]
+type=service
+router= readwritesplit
+servers=server1, server2, server3
+user=maxskysql
+passwd=skysql
+
+[RW Split Listener]
+type=listener
+service=RW Split Router
+protocol=MySQLClient
+port=4006
+
+[CLI]
+type=service
+router=cli
+
+[CLI Listener]
+type=listener
+service=CLI
+protocol=maxscaled
+socket=default
+
+[server1]
+type=server
+address=###node_server_IP_1###
+port=###node_server_port_1###
+protocol=MySQLBackend
+
+[server2]
+type=server
+address=###node_server_IP_2###
+port=###node_server_port_2###
+protocol=MySQLBackend
+
+[server3]
+type=server
+address=###node_server_IP_3###
+port=###node_server_port_3###
+protocol=MySQLBackend

maxscale-system-test/mxs1961_standalone_rejoin.cpp

@@ -0,0 +1,143 @@
+/**
+ * MXS-1961: Standalone master loses master status
+ */
+
+#include "testconnections.h"
+#include <iostream>
+
+using namespace std;
+
+void checkpoint(TestConnections& test)
+{
+    const int v = 5;
+    test.maxscales->wait_for_monitor(v);
+
+    for (auto&& s: {"server1", "server2", "server3"})
+    {
+        auto status = test.get_server_status(s);
+        cout << s << " { ";
+        for (auto a: status)
+        {
+            cout << a << ", ";
+        }
+        cout << "}\n";
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    Mariadb_nodes::require_gtid(true);
+    TestConnections test(argc, argv);
+
+    auto status = [&](const char* server)
+    {
+        return test.get_server_status(server);
+    };
+
+    auto comment = [&](const char* comment)
+    {
+        cout << comment << endl;
+        test.maxscales->ssh_node_f(0, true, "echo '----- %s -----' >> /var/log/maxscale/maxscale.log", comment);
+    };
+
+    auto slave = [&](const char* name)
+    {
+        static StringSet slave{"Slave", "Running"};
+        test.assert(status(name) == slave, "'%s' should be a slave", name);
+    };
+
+    auto master = [&](const char* name)
+    {
+        static StringSet master{"Master", "Running"};
+        test.assert(status(name) == master, "'%s' should be the master", name);
+    };
+
+    auto down = [&](const char* name)
+    {
+        static StringSet down{"Down"};
+        test.assert(status(name) == down, "'%s' should be down", name);
+    };
+
+    auto block = [&](int node)
+    {
+        test.repl->block_node(node);
+        checkpoint(test);
+    };
+
+    auto unblock = [&](int node)
+    {
+        test.repl->unblock_node(node);
+        checkpoint(test);
+    };
+
+    test.maxscales->wait_for_monitor(1);
+
+    master("server1");
+    slave("server2");
+    slave("server3");
+
+    comment("Blocking server1");
+    block(0);
+    comment("Blocking server2");
+    block(1);
+
+    down("server1");
+    down("server2");
+    master("server3");
+
+    comment("Unblocking server2");
+    unblock(1);
+
+    down("server1");
+    slave("server2");
+    master("server3");
+
+    comment("Blocking server3");
+    block(2);
+    comment("Unblocking server3");
+    unblock(2);
+
+    down("server1");
+    master("server2");
+    slave("server3");
+
+    comment("Blocking server3");
+    block(2);
+
+    down("server1");
+    master("server2");
+    down("server3");
+
+    comment("Unblocking server1");
+    unblock(0);
+
+    slave("server1");
+    master("server2");
+    down("server3");
+
+    comment("Blocking server2");
+    block(1);
+
+    master("server1");
+    down("server2");
+    down("server3");
+
+    comment("Unblocking server2");
+    unblock(1);
+
+    master("server1");
+    slave("server2");
+    down("server3");
+
+    comment("Unblocking server3");
+    unblock(2);
+
+    master("server1");
+    slave("server2");
+    slave("server3");
+
+    test.maxscales->stop();
+    test.repl->fix_replication();
+
+    return test.global_result;
+}