Added CPP-HTTPLIB-based version of the meta module

src/http/CMakeLists.txt

@@ -3,6 +3,7 @@ add_library(http SHARED)
 target_sources(http PRIVATE
     AsyncReq.cc
     BinaryEncoding.cc
+    ChttpMetaModule.cc
     ChttpModule.cc
     Client.cc
     ClientConnPool.cc

src/http/ChttpMetaModule.cc

@@ -0,0 +1,71 @@
+/*
+ * LSST Data Management System
+ *
+ * This product includes software developed by the
+ * LSST Project (http://www.lsst.org/).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the LSST License Statement and
+ * the GNU General Public License along with this program.  If not,
+ * see <http://www.lsstcorp.org/LegalNotices/>.
+ */
+
+// Class header
+#include "http/ChttpMetaModule.h"
+
+// System headers
+#include <stdexcept>
+
+using namespace std;
+using json = nlohmann::json;
+
+namespace {
+// Authorization context is not required by this module
+lsst::qserv::http::AuthType const authType = lsst::qserv::http::AuthType::NONE;
+string const authKey;
+string const adminAuthKey;
+}  // namespace
+
+namespace lsst::qserv::http {
+
+unsigned int const ChttpMetaModule::version = 35;
+
+void ChttpMetaModule::process(string const& context, nlohmann::json const& info, httplib::Request const& req,
+                              httplib::Response& resp, string const& subModuleName) {
+    ChttpMetaModule module(context, info, req, resp);
+    module.execute(subModuleName, ::authType);
+}
+
+ChttpMetaModule::ChttpMetaModule(string const& context, nlohmann::json const& info,
+                                 httplib::Request const& req, httplib::Response& resp)
+        : http::ChttpModule(::authKey, ::adminAuthKey, req, resp), _context(context), _info(info) {
+    if (!_info.is_object()) {
+        throw invalid_argument("ChttpMetaModule::" + string(__func__) + " parameter info must be an object.");
+    }
+}
+
+json ChttpMetaModule::executeImpl(string const& subModuleName) {
+    if (subModuleName == "VERSION") return _version();
+    throw invalid_argument(context() + "::" + string(__func__) + "  unsupported sub-module: '" +
+                           subModuleName + "'");
+}
+
+string ChttpMetaModule::context() const { return _context; }
+
+json ChttpMetaModule::_version() {
+    debug(__func__);
+    json result = _info;
+    result["version"] = ChttpMetaModule::version;
+    return result;
+}
+
+}  // namespace lsst::qserv::http

src/http/ChttpMetaModule.h

@@ -0,0 +1,80 @@
+/*
+ * LSST Data Management System
+ *
+ * This product includes software developed by the
+ * LSST Project (http://www.lsst.org/).
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the LSST License Statement and
+ * the GNU General Public License along with this program.  If not,
+ * see <http://www.lsstcorp.org/LegalNotices/>.
+ */
+#ifndef LSST_QSERV_HTTP_CHTTPMETAMODULE_H
+#define LSST_QSERV_HTTP_CHTTPMETAMODULE_H
+
+// System headers
+#include <memory>
+#include <string>
+
+// Third party headers
+#include "nlohmann/json.hpp"
+
+// Qserv headers
+#include "http/ChttpModule.h"
+
+// This header declarations
+namespace lsst::qserv::http {
+
+/**
+ * Class ChttpMetaModule implements a handler for the metadata queries on the REST API itself.
+ * The service responds with an information object provided at the creation time of the module.
+ */
+class ChttpMetaModule : public http::ChttpModule {
+public:
+    typedef std::shared_ptr<ChttpMetaModule> Ptr;
+
+    /// The current version of the REST API
+    static unsigned int const version;
+
+    /**
+     * @note supported values for parameter 'subModuleName' are:
+     *   'VERSION' - return a version of the REST API
+     *
+     * @param info The information object to be returned to clients of the service.
+     * @throws std::invalid_argument for unknown values of parameter 'subModuleName'
+     */
+    static void process(std::string const& context, nlohmann::json const& info, httplib::Request const& req,
+                        httplib::Response& resp, std::string const& subModuleName);
+
+    ChttpMetaModule() = delete;
+    ChttpMetaModule(ChttpMetaModule const&) = delete;
+    ChttpMetaModule& operator=(ChttpMetaModule const&) = delete;
+
+    ~ChttpMetaModule() final = default;
+
+protected:
+    virtual nlohmann::json executeImpl(std::string const& subModuleName) final;
+    virtual std::string context() const final;
+
+private:
+    ChttpMetaModule(std::string const& context, nlohmann::json const& info, httplib::Request const& req,
+                    httplib::Response& resp);
+
+    nlohmann::json _version();
+
+    std::string const _context;
+    nlohmann::json const _info;
+};
+
+}  // namespace lsst::qserv::http
+
+#endif  // LSST_QSERV_HTTP_CHTTPMETAMODULE_H