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CXX-890 Don't use objects requiring dynamic init/fini for instance::c…
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// Copyright 2016 MongoDB Inc. | ||
// | ||
// Licensed under the Apache License, Version 2.0 (the "License"); | ||
// you may not use this file except in compliance with the License. | ||
// You may obtain a copy of the License at | ||
// | ||
// http://www.apache.org/licenses/LICENSE-2.0 | ||
// | ||
// Unless required by applicable law or agreed to in writing, software | ||
// distributed under the License is distributed on an "AS IS" BASIS, | ||
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
// See the License for the specific language governing permissions and | ||
// limitations under the License. | ||
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#include <cstdlib> | ||
#include <memory> | ||
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#include <bsoncxx/stdx/make_unique.hpp> | ||
#include <bsoncxx/stdx/optional.hpp> | ||
#include <bsoncxx/stdx/string_view.hpp> | ||
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#include <mongocxx/instance.hpp> | ||
#include <mongocxx/logger.hpp> | ||
#include <mongocxx/pool.hpp> | ||
#include <mongocxx/stdx.hpp> | ||
#include <mongocxx/uri.hpp> | ||
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namespace { | ||
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// This example demonstrates how one might keep a heap allocated mongocxx::instance and | ||
// mongocxx::pool object associated in a way that allows dynamic configuration. Most of the examples | ||
// simply create a stack allocated mongocxx::instance object, which is fine for small examples, but | ||
// real programs will typically require shared access to a commonly configured instance and | ||
// connection pool across different translation units and components. By providing a singleton which | ||
// owns the instance and pool objects, we can defer configuration until we are ready to use MongoDB, | ||
// and share the instance and pool objects between multiple functions. | ||
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class mongo_access { | ||
public: | ||
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static mongo_access& instance() { | ||
static mongo_access instance; | ||
return instance; | ||
} | ||
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void configure(std::unique_ptr<mongocxx::instance> instance, | ||
std::unique_ptr<mongocxx::pool> pool) { | ||
_instance = std::move(instance); | ||
_pool = std::move(pool); | ||
} | ||
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using connection = mongocxx::pool::entry; | ||
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connection get_connection() { | ||
return _pool->acquire(); | ||
} | ||
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mongocxx::stdx::optional<connection> try_get_connection() { | ||
return _pool->try_acquire(); | ||
} | ||
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private: | ||
mongo_access() = default; | ||
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std::unique_ptr<mongocxx::instance> _instance = nullptr; | ||
std::unique_ptr<mongocxx::pool> _pool = nullptr; | ||
}; | ||
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} // namespace | ||
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// The 'configure' and 'do_work' functions use the same mongocxx::instance and mongocxx::pool | ||
// objects by way of the mongo_access singleton. | ||
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void configure(mongocxx::uri uri) { | ||
class noop_logger : public mongocxx::logger { | ||
public: | ||
virtual void operator()(mongocxx::log_level, mongocxx::stdx::string_view, | ||
mongocxx::stdx::string_view message) noexcept {} | ||
}; | ||
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mongo_access::instance().configure( | ||
mongocxx::stdx::make_unique<mongocxx::instance>(mongocxx::stdx::make_unique<noop_logger>()), | ||
mongocxx::stdx::make_unique<mongocxx::pool>(std::move(uri)) | ||
); | ||
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} | ||
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bool do_work() { | ||
auto connection = mongo_access::instance().get_connection(); | ||
if (!connection) | ||
return false; | ||
return true; | ||
} | ||
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int main(int argc, char* argv[]) { | ||
auto uri = mongocxx::uri{(argc >= 2) ? argv[1] : mongocxx::uri::k_default_uri}; | ||
configure(std::move(uri)); | ||
return do_work() ? EXIT_SUCCESS : EXIT_FAILURE; | ||
} |
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