MXS-1752: Add prototype concatenation router

The router concatenates multiple result sets.

server/modules/routing/cat/cat.cc

@@ -0,0 +1,94 @@
+/*
+ * 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 "cat.hh"
+#include "catsession.hh"
+
+using namespace maxscale;
+
+Cat::Cat(SERVICE* pService):
+    Router<Cat, CatSession>(pService)
+{
+}
+
+Cat::~Cat()
+{
+}
+
+Cat* Cat::create(SERVICE* pService, char** pzOptions)
+{
+    return new Cat(pService);
+}
+
+CatSession* Cat::newSession(MXS_SESSION* pSession)
+{
+    auto backends = RWBackend::from_servers(pSession->service->dbref);
+
+    for (auto a = backends.begin(); a != backends.end(); a++)
+    {
+        (*a)->connect(pSession);
+    }
+
+    return new CatSession(pSession, this, backends);
+}
+
+void Cat::diagnostics(DCB* dcb)
+{
+}
+
+json_t* Cat::diagnostics_json() const
+{
+    return NULL;
+}
+
+const uint64_t caps = RCAP_TYPE_STMT_OUTPUT | RCAP_TYPE_STMT_INPUT;
+
+uint64_t Cat::getCapabilities()
+{
+    return caps;
+}
+
+MXS_BEGIN_DECLS
+
+/**
+ * The module entry point routine. It is this routine that
+ * must populate the structure that is referred to as the
+ * "module object", this is a structure with the set of
+ * external entry points for this module.
+ *
+ * @return The module object
+ */
+MXS_MODULE* MXS_CREATE_MODULE()
+{
+    static MXS_MODULE info =
+    {
+        MXS_MODULE_API_ROUTER,
+        MXS_MODULE_ALPHA_RELEASE,
+        MXS_ROUTER_VERSION,
+        "Resultset concatenation router",
+        "V1.0.0",
+        caps,
+        &Cat::s_object,
+        NULL, /* Process init. */
+        NULL, /* Process finish. */
+        NULL, /* Thread init. */
+        NULL, /* Thread finish. */
+        {
+            {MXS_END_MODULE_PARAMS}
+        }
+    };
+
+    return &info;
+}
+
+MXS_END_DECLS