Allow injection of external CivetServer via Exposer constructor

core/include/prometheus/detail/future_std.h

@@ -6,11 +6,14 @@
 namespace prometheus {
 namespace detail {
 
-// Remove as soon C++14 can be used.
+#if __cplusplus >= 201402L
+using std::make_unique;
+#else
 template <typename T, typename... Args>
 std::unique_ptr<T> make_unique(Args&&... args) {
   return std::unique_ptr<T>(new T(std::forward<Args>(args)...));
 }
+#endif
 
 }  // namespace detail
 }  // namespace prometheus

pull/include/prometheus/exposer.h

@@ -21,6 +21,7 @@ class Endpoint;
 
 class PROMETHEUS_CPP_PULL_EXPORT Exposer {
  public:
+  explicit Exposer(std::shared_ptr<CivetServer> server);
   explicit Exposer(const std::string& bind_address, std::size_t num_threads = 2,
                    const CivetCallbacks* callbacks = nullptr);
   explicit Exposer(std::vector<std::string> options,
@@ -48,7 +49,7 @@ class PROMETHEUS_CPP_PULL_EXPORT Exposer {
  private:
   detail::Endpoint& GetEndpointForUri(const std::string& uri);
 
-  std::unique_ptr<CivetServer> server_;
+  std::shared_ptr<CivetServer> server_;
   std::vector<std::unique_ptr<detail::Endpoint>> endpoints_;
   std::mutex mutex_;
 };

pull/src/exposer.cc

@@ -11,6 +11,13 @@
 
 namespace prometheus {
 
+Exposer::Exposer(std::shared_ptr<CivetServer> server)
+    : server_(std::move(server)) {
+  if (!server_) {
+    throw std::invalid_argument("Invalid CivetServer: cannot be null");
+  }
+} 
+
 Exposer::Exposer(const std::string& bind_address, const std::size_t num_threads,
                  const CivetCallbacks* callbacks)
     : Exposer(
@@ -20,7 +27,7 @@ Exposer::Exposer(const std::string& bind_address, const std::size_t num_threads,
 
 Exposer::Exposer(std::vector<std::string> options,
                  const CivetCallbacks* callbacks)
-    : server_(detail::make_unique<CivetServer>(std::move(options), callbacks)) {
+    : Exposer(std::make_shared<CivetServer>(std::move(options), callbacks)) {
 }
 
 Exposer::~Exposer() = default;

pull/tests/unit/exposer_test.cc

@@ -2,6 +2,8 @@
 
 #include <gtest/gtest.h>
 
+#include "CivetServer.h"
+
 namespace prometheus {
 namespace {
 
@@ -21,5 +23,9 @@ TEST(ExposerTest, listenOnDistinctPorts) {
   EXPECT_NE(firstExposerPorts, secondExposerPorts);
 }
 
+TEST(ExposerTest, invalidExternalServer) {
+  EXPECT_THROW(Exposer(std::shared_ptr<CivetServer>(nullptr)), std::invalid_argument);
+}
+
 }  // namespace
 }  // namespace prometheus