MXS-1418: Keep connections open if server is removed

The removal of a server from a service is intended to affect only new
sessions.

Added a test that checks that the connections are kept open even if the
server is removed from the service.

maxscale-system-test/mxs1418.cpp

@@ -0,0 +1,73 @@
+/**
+ * @file Check that removing a server from a service doesn't break active connections
+ */
+
+#include "testconnections.h"
+
+static volatile bool running = true;
+
+void* thr(void* data)
+{
+    TestConnections* test = (TestConnections*)data;
+
+    while (running && test->global_result == 0)
+    {
+        test->set_timeout(60);
+        if (test->try_query(test->conn_rwsplit, "SELECT 1"))
+        {
+            test->tprintf("Failed to select via readwritesplit");
+        }
+        if (test->try_query(test->conn_master, "SELECT 1"))
+        {
+            test->tprintf("Failed to select via readconnroute master");
+        }
+        if (test->try_query(test->conn_slave, "SELECT 1"))
+        {
+            test->tprintf("Failed to select via readconnroute slave");
+        }
+    }
+
+    test->stop_timeout();
+
+    return NULL;
+}
+
+int main(int argc, char *argv[])
+{
+    TestConnections test(argc, argv);
+    test.connect_maxscale();
+
+    test.tprintf("Connect to MaxScale and continuously execute queries");
+    pthread_t thread;
+    pthread_create(&thread, NULL, thr, &test);
+    sleep(5);
+
+    test.tprintf("Remove all servers from all services");
+
+    for (int i = 3; i > -1; i--)
+    {
+        test.ssh_maxscale(true, "maxadmin remove server server%d \"RW Split Router\"", i);
+        test.ssh_maxscale(true, "maxadmin remove server server%d \"Read Connection Router Slave\"", i);
+        test.ssh_maxscale(true, "maxadmin remove server server%d \"Read Connection Router Master\"", i);
+    }
+
+    sleep(5);
+
+    test.tprintf("Stop queries and close the connections");
+    running = false;
+    pthread_join(thread, NULL);
+    test.close_maxscale_connections();
+
+    test.tprintf("Add all servers to all services");
+
+    for (int i = 3; i > -1; i--)
+    {
+        test.ssh_maxscale(true, "maxadmin add server server%d \"RW Split Router\"", i);
+        test.ssh_maxscale(true, "maxadmin add server server%d \"Read Connection Router Slave\"", i);
+        test.ssh_maxscale(true, "maxadmin add server server%d \"Read Connection Router Master\"", i);
+    }
+
+    test.check_maxscale_alive();
+
+    return test.global_result;
+}