From a3c47cc6823d017056b4790db88769fc6f6f40de Mon Sep 17 00:00:00 2001
From: Sandor Magyar <SMagyar@aphysci.com>
Date: Mon, 17 Oct 2022 17:32:08 -0400
Subject: [PATCH] Don't force Mongo sink to own MongoCXX instance

There can only be one instance in the whole program, so programs that use the
Mongo sink and also separately use MongoCXX may have problems if the Mongo sink
owns the instance. MongoCXX recommends that the main application manage its own
instance so configuration parameters can be passed to the constructor:
http://mongocxx.org/api/current/classmongocxx_1_1instance.html

However, this commit is not a breaking change. If no instance has been created
at construction time, the Mongo sink will still create and own the instance.
---
 include/spdlog/sinks/mongo_sink.h | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/include/spdlog/sinks/mongo_sink.h b/include/spdlog/sinks/mongo_sink.h
index 1338983c..ab8a5b4d 100644
--- a/include/spdlog/sinks/mongo_sink.h
+++ b/include/spdlog/sinks/mongo_sink.h
@@ -20,6 +20,7 @@
 #include <bsoncxx/view_or_value.hpp>
 
 #include <mongocxx/client.hpp>
+#include <mongocxx/exception/logic_error.hpp>
 #include <mongocxx/instance.hpp>
 #include <mongocxx/uri.hpp>
 
@@ -29,10 +30,23 @@ template<typename Mutex>
 class mongo_sink : public base_sink<Mutex>
 {
 public:
-    mongo_sink(const std::string &db_name, const std::string &collection_name, const std::string &uri = "mongodb://localhost:27017")
+    mongo_sink(const std::string &db_name, const std::string &collection_name, const std::string &uri = "mongodb://localhost:27017",
+        bool create_instance = true)
     {
         try
         {
+            if (create_instance && !instance_)
+            {
+                try
+                {
+                    instance_ = std::make_shared<mongocxx::instance>();
+                }
+                catch (const mongocxx::logic_error&)
+                {
+                    // A MongoCXX instance already exists, so this object doesn't need to own it
+                    instance_ = nullptr;
+                }
+            }
             client_ = spdlog::details::make_unique<mongocxx::client>(mongocxx::uri{uri});
             db_name_ = db_name;
             coll_name_ = collection_name;
@@ -68,13 +82,13 @@ protected:
     void flush_() override {}
 
 private:
-    static mongocxx::instance instance_;
+    static std::shared_ptr<mongocxx::instance> instance_;
     std::string db_name_;
     std::string coll_name_;
     std::unique_ptr<mongocxx::client> client_ = nullptr;
 };
 template<>
-mongocxx::instance mongo_sink<std::mutex>::instance_{};
+std::shared_ptr<mongocxx::instance> mongo_sink<std::mutex>::instance_{};
 
 #include "spdlog/details/null_mutex.h"
 #include <mutex>