Add NullFilter filter module

NullFilter is a filter module that does nothing, except reports
capabilities as defined in the configuration file. It's purpose
is only to make it simple to benchmark the performance impact
various routing capabilities have.

Note that since getCapabilities() currently does *not* take an
instance pointer as parameter, all NullFilter instances will
report the same capabilities, the ones specified for the last
filter to have been loaded.

server/modules/filter/CMakeLists.txt

@@ -6,6 +6,7 @@ add_subdirectory(hintfilter)
 add_subdirectory(luafilter)
 add_subdirectory(mqfilter)
 add_subdirectory(namedserverfilter)
+add_subdirectory(nullfilter)
 add_subdirectory(qlafilter)
 add_subdirectory(regexfilter)
 add_subdirectory(tee)

server/modules/filter/nullfilter/CMakeLists.txt

@@ -0,0 +1,7 @@
+add_library(nullfilter SHARED
+  nullfilter.cc
+  nullfiltersession.cc
+  )
+target_link_libraries(nullfilter maxscale-common)
+set_target_properties(nullfilter PROPERTIES VERSION "1.0.0")
+install_module(nullfilter core)

server/modules/filter/nullfilter/nullfilter.cc

@@ -0,0 +1,133 @@
+/*
+ * 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/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * 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.
+ */
+
+#define MXS_MODULE_NAME "nullfilter"
+#include "nullfilter.hh"
+#include <string>
+#include <maxscale/utils.h>
+
+using std::string;
+
+namespace
+{
+
+#define VERSION_STRING "V1.0.0"
+
+const char CAPABILITIES_PARAM[] = "capabilities";
+
+MXS_ENUM_VALUE capability_values[] =
+{
+    { "RCAP_TYPE_STMT_INPUT",           RCAP_TYPE_STMT_INPUT },
+    { "RCAP_TYPE_CONTIGUOUS_INPUT",     RCAP_TYPE_CONTIGUOUS_INPUT },
+    { "RCAP_TYPE_TRANSACTION_TRACKING", RCAP_TYPE_TRANSACTION_TRACKING },
+    { "RCAP_TYPE_STMT_OUTPUT",          RCAP_TYPE_STMT_OUTPUT },
+    { "RCAP_TYPE_CONTIGUOUS_OUTPUT",    RCAP_TYPE_CONTIGUOUS_OUTPUT },
+    { "RCAP_TYPE_RESULTSET_OUTPUT",     RCAP_TYPE_RESULTSET_OUTPUT },
+    { NULL, 0 }
+};
+
+struct unit_variables
+{
+    uint64_t capabilities;
+    bool     capabilities_set;
+} this_unit =
+{
+    0,
+    false
+};
+
+}
+
+//
+// Global symbols of the Module
+//
+
+extern "C" MXS_MODULE* MXS_CREATE_MODULE()
+{
+    MXS_NOTICE("Nullfilter module %s initialized.", VERSION_STRING);
+
+    static MXS_MODULE info =
+    {
+        MXS_MODULE_API_FILTER,
+        MXS_MODULE_IN_DEVELOPMENT,
+        MXS_FILTER_VERSION,
+        "A null filter that does nothing.",
+        VERSION_STRING,
+        &NullFilter::s_object,
+        NULL, /* Process init. */
+        NULL, /* Process finish. */
+        NULL, /* Thread init. */
+        NULL, /* Thread finish. */
+        {
+            { CAPABILITIES_PARAM, MXS_MODULE_PARAM_ENUM, NULL, MXS_MODULE_OPT_REQUIRED, capability_values },
+            { MXS_END_MODULE_PARAMS }
+        }
+    };
+
+    return &info;
+}
+
+//
+// NullFilter
+//
+
+NullFilter::NullFilter(const char* zName)
+{
+    MXS_NOTICE("Null filter [%s] created.", zName);
+}
+
+NullFilter::~NullFilter()
+{
+}
+
+// static
+NullFilter* NullFilter::create(const char* zName, char**, MXS_CONFIG_PARAMETER* pParams)
+{
+    NullFilter* pFilter = NULL;
+
+    uint64_t capabilities = config_get_enum(pParams, CAPABILITIES_PARAM, capability_values);
+
+    if (this_unit.capabilities_set)
+    {
+        MXS_WARNING("The capabilities reported by NullFilter are currently global, "
+                    "and not specific for a particular NullFilter instance.");
+    }
+
+    this_unit.capabilities = capabilities;
+    this_unit.capabilities_set = true;
+
+    return new NullFilter(zName);
+}
+
+
+NullFilterSession* NullFilter::newSession(MXS_SESSION* pSession)
+{
+    return NullFilterSession::create(pSession, this);
+}
+
+// static
+void NullFilter::diagnostics(DCB* pDcb)
+{
+    dcb_printf(pDcb, "Hello, World!\n");
+}
+
+// static
+uint64_t NullFilter::getCapabilities()
+{
+    if (!this_unit.capabilities_set)
+    {
+        MXS_ERROR("getCapabilities() called before they have been set.");
+    }
+
+    return this_unit.capabilities;
+}

server/modules/filter/nullfilter/nullfilter.hh

@@ -0,0 +1,36 @@
+#pragma once
+/*
+ * 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/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * 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 <maxscale/cppdefs.hh>
+#include <maxscale/filter.hh>
+#include "nullfiltersession.hh"
+
+class NullFilter : public maxscale::Filter<NullFilter, NullFilterSession>
+{
+public:
+    ~NullFilter();
+    static NullFilter* create(const char* zName, char** pzOptions, MXS_CONFIG_PARAMETER* pParams);
+
+    NullFilterSession* newSession(MXS_SESSION* pSession);
+
+    void diagnostics(DCB* pDcb);
+
+    static uint64_t getCapabilities();
+
+private:
+    NullFilter(const char* zName);
+
+    NullFilter(const NullFilter&);
+    NullFilter& operator = (const NullFilter&);
+};

server/modules/filter/nullfilter/nullfiltersession.cc

@@ -0,0 +1,31 @@
+/*
+ * 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/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * 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.
+ */
+
+#define MXS_MODULE_NAME "nullfilter"
+#include "nullfiltersession.hh"
+
+NullFilterSession::NullFilterSession(MXS_SESSION* pSession, const NullFilter* pFilter)
+    : maxscale::FilterSession(pSession)
+    , m_filter(*pFilter)
+{
+}
+
+NullFilterSession::~NullFilterSession()
+{
+}
+
+//static
+NullFilterSession* NullFilterSession::create(MXS_SESSION* pSession, const NullFilter* pFilter)
+{
+    return new NullFilterSession(pSession, pFilter);
+}

server/modules/filter/nullfilter/nullfiltersession.hh

@@ -0,0 +1,35 @@
+#pragma once
+/*
+ * 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/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * 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 <maxscale/cppdefs.hh>
+#include <maxscale/filter.hh>
+
+class NullFilter;
+
+class NullFilterSession : public maxscale::FilterSession
+{
+public:
+    ~NullFilterSession();
+
+    static NullFilterSession* create(MXS_SESSION* pSession, const NullFilter* pFilter);
+
+private:
+    NullFilterSession(MXS_SESSION* pSession, const NullFilter* pFilter);
+
+    NullFilterSession(const NullFilterSession&);
+    NullFilterSession& operator = (const NullFilterSession&);
+
+private:
+    const NullFilter& m_filter;
+};