MXS-2919: Add test case

The test checks that no slaves are used when the replication lag is not
measurable.

maxscale-system-test/CMakeLists.txt

@@ -942,6 +942,9 @@ add_test_executable(mxs2878_monitor_ssl.cpp mxs2878_monitor_ssl mxs2878_monitor_
 # MXS-2939: Test that session commands trigger a reconnection
 add_test_executable(mxs2939_sescmd_reconnect.cpp mxs2939_sescmd_reconnect mxs2939_sescmd_reconnect LABELS REPL_BACKEND readwritesplit)
 
+# MXS-2919: Slaves with broken replication should not be used
+add_test_executable(mxs2919_broken_slaves.cpp mxs2919_broken_slaves mxs2919_broken_slaves LABELS REPL_BACKEND readwritesplit)
+
 ############################################
 # END: Normal tests                        #
 ############################################

maxscale-system-test/cnf/maxscale.cnf.template.mxs2919_broken_slaves

@@ -0,0 +1,26 @@
+[maxscale]
+threads=###threads###
+
+###server###
+
+[MySQL-Monitor]
+type=monitor
+module=mysqlmon
+servers=###server_line###
+user=maxskysql
+password=skysql
+monitor_interval=1s
+
+[RW-Split-Router]
+type=service
+router=readwritesplit
+servers=###server_line###
+user=maxskysql
+password=skysql
+max_slave_replication_lag=1
+
+[RW-Split-Listener]
+type=listener
+service=RW-Split-Router
+protocol=MySQLClient
+port=4006

maxscale-system-test/maxtest/include/maxtest/mariadb_nodes.h

@@ -242,6 +242,16 @@ public:
     // Create the default users used by all tests
     void create_users(int node);
 
+    /**
+     * Blocks `src` from communicating with `dest`
+     */
+    void block_node_from_node(int src, int dest);
+
+    /**
+     * Unblocks the block added by block_node_from_node
+     */
+    void unblock_node_from_node(int src, int dest);
+
     /**
      * @param node Index of node to block.
      * @return The command used for blocking a node.

maxscale-system-test/maxtest/src/mariadb_nodes.cc

@@ -510,11 +510,31 @@ int Mariadb_nodes::clean_iptables(int node)
     return ssh_node_f(node,
                       true,
                       "while [ \"$(iptables -n -L INPUT 1|grep '%d')\" != \"\" ]; do iptables -D INPUT 1; done;"
-                      "while [ \"$(ip6tables -n -L INPUT 1|grep '%d')\" != \"\" ]; do ip6tables -D INPUT 1; done;",
+                      "while [ \"$(ip6tables -n -L INPUT 1|grep '%d')\" != \"\" ]; do ip6tables -D INPUT 1; done;"
+                      "while [ \"$(iptables -n -L OUTPUT 1|grep '3306')\" != \"\" ]; do iptables -D OUTPUT 1; done;",
                       port[node],
                       port[node]);
 }
 
+
+void Mariadb_nodes::block_node_from_node(int src, int dest)
+{
+    std::ostringstream ss;
+
+    ss << "iptables -I OUTPUT 1 -p tcp -d " << IP[dest] << " --dport 3306 -j DROP;";
+
+    ssh_node_f(src, true, "%s", ss.str().c_str());
+}
+
+void Mariadb_nodes::unblock_node_from_node(int src, int dest)
+{
+    std::ostringstream ss;
+
+    ss << "iptables -D OUTPUT -p tcp -d " << IP[dest] << " --dport 3306 -j DROP;";
+
+    ssh_node_f(src, true, "%s", ss.str().c_str());
+}
+
 std::string Mariadb_nodes::block_command(int node) const
 {
     const char FORMAT[] =

maxscale-system-test/mxs2919_broken_slaves.cpp

@@ -0,0 +1,43 @@
+/**
+ * MXS-2919: Slaves that aren't replicating should not be used for reads when max_slave_replication_lag is
+ * used.
+ */
+
+#include "testconnections.h"
+
+int main(int argc, char** argv)
+{
+    TestConnections test(argc, argv);
+
+    auto conn = test.maxscales->rwsplit();
+    test.expect(conn.connect(), "Connection should work");
+
+    std::string master_id = conn.field("SELECT @@server_id, @@last_insert_id", 0);
+
+    test.repl->connect();
+
+    for (int i = 1; i < test.repl->N; i++)
+    {
+        test.repl->block_node_from_node(i, 0);
+        test.try_query(test.repl->nodes[i], "STOP SLAVE;START SLAVE");
+    }
+
+    test.repl->disconnect();
+    test.maxscales->wait_for_monitor();
+
+    for (int i = 0; test.ok() && i < 50; i++)
+    {
+        auto current_id = conn.field("SELECT @@server_id");
+
+        test.expect(current_id == master_id,
+                    "The query was not routed to the master: %s%s",
+                    current_id.c_str(), conn.error());
+    }
+
+    for (int i = 1; i < test.repl->N; i++)
+    {
+        test.repl->unblock_node_from_node(i, 0);
+    }
+
+    return test.global_result;
+}