MXS-1506: Add cluster failure test

The test exercises the retrying code by failing both nodes.

maxscale-system-test/CMakeLists.txt

@@ -606,6 +606,10 @@ add_test_executable(mxs1503_extra_slaves.cpp mxs1503_extra_slaves mxs1503_extra_
 # https://jira.mariadb.org/browse/MXS-1506
 add_test_executable(mxs1506_delayed_retry.cpp mxs1506_delayed_retry mxs1506_delayed_retry LABELS readwritesplit REPL_BACKEND)
 
+# MXS-1506: Delayed retry without master
+# https://jira.mariadb.org/browse/MXS-1506
+add_test_executable(mxs1506_no_master.cpp mxs1506_no_master mxs1506_delayed_retry LABELS readwritesplit REPL_BACKEND)
+
 # MXS-1509: Show correct server state for multisource replication
 # https://jira.mariadb.org/browse/MXS-1509
 add_test_executable(mxs1509.cpp mxs1509 mxs1509 LABELS mysqlmon REPL_BACKEND)

maxscale-system-test/mxs1506_no_master.cpp

@@ -0,0 +1,61 @@
+/**
+ * MXS-1506: Delayed query retry without master
+ *
+ * https://jira.mariadb.org/browse/MXS-1506
+ */
+#include "testconnections.h"
+#include <string>
+#include <functional>
+#include <thread>
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+bool query(TestConnections& test)
+{
+    test.maxscales->connect();
+    execute_query_silent(test.maxscales->conn_rwsplit[0], "SET @a = 1") == 0;
+    sleep(5);
+    auto row = get_row(test.maxscales->conn_rwsplit[0], "SELECT @a");
+    test.maxscales->disconnect();
+    return row[0] == "1";
+}
+
+void block(TestConnections& test, std::vector<int> nodes)
+{
+    for (auto a : nodes)
+    {
+        test.repl->block_node(a);
+    }
+
+    sleep(10);
+
+    for (auto a : nodes)
+    {
+        test.repl->unblock_node(a);
+    }
+}
+
+int main(int argc, char** argv)
+{
+    TestConnections test(argc, argv);
+    thread thr;
+
+    cout << "Blocking the master and executing a SELECT" << endl;
+    thr = thread(block, std::ref(test), vector<int>({0}));
+    test.assert(query(test), "Select without master should work");
+    thr.join();
+
+    cout << "Blocking the slave and executing a SELECT" << endl;
+    thr = thread(block, std::ref(test), vector<int>({1}));
+    test.assert(query(test), "Select without slave should work");
+    thr.join();
+
+    cout << "Blocking both servers and executing a SELECT" << endl;
+    thr = thread(block, std::ref(test), vector<int>({0, 1}));
+    test.assert(query(test), "Select with no servers should work");
+    thr.join();
+
+    return test.global_result;
+}