From eabcab26ed8acdb70148f06ea940d63fdada4128 Mon Sep 17 00:00:00 2001
From: gaschler <gaschlera@gmail.com>
Date: Wed, 21 Feb 2018 18:52:57 +0100
Subject: [PATCH] Expose metrics as http page. (#920)

RFC=[0014](https://github.com/googlecartographer/rfcs/blob/master/text/0014-monitoring.md)
---
 CMakeLists.txt                                      |  2 +-
 cartographer_grpc/map_builder_server_main.cc        | 13 +++++++++++++
 .../metrics/prometheus/metrics_test.cc              | 11 +++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index a0bea81..9161dd8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -217,7 +217,7 @@ if(${BUILD_GRPC})
 endif()
 if(${BUILD_PROMETHEUS})
   target_link_libraries(${PROJECT_NAME} PUBLIC prometheus-cpp)
-  target_compile_definitions(${PROJECT_NAME} PRIVATE USE_PROMETHEUS=1)
+  target_compile_definitions(${PROJECT_NAME} PUBLIC USE_PROMETHEUS=1)
 endif()
 
 # Add the binary directory first, so that port.h is included after it has
diff --git a/cartographer_grpc/map_builder_server_main.cc b/cartographer_grpc/map_builder_server_main.cc
index 4b6f3cb..094a2dc 100644
--- a/cartographer_grpc/map_builder_server_main.cc
+++ b/cartographer_grpc/map_builder_server_main.cc
@@ -14,10 +14,15 @@
  * limitations under the License.
  */
 
+#include "cartographer/metrics/register.h"
 #include "cartographer_grpc/map_builder_server.h"
 #include "cartographer_grpc/map_builder_server_options.h"
 #include "gflags/gflags.h"
 #include "glog/logging.h"
+#if USE_PROMETHEUS
+#include "cartographer_grpc/metrics/prometheus/family_factory.h"
+#include "prometheus/exposer.h"
+#endif
 
 DEFINE_string(configuration_directory, "",
               "First directory in which configuration files are searched, "
@@ -31,6 +36,14 @@ namespace cartographer_grpc {
 
 void Run(const std::string& configuration_directory,
          const std::string& configuration_basename) {
+#if USE_PROMETHEUS
+  metrics::prometheus::FamilyFactory registry;
+  cartographer::metrics::RegisterAllMetrics(&registry);
+  ::prometheus::Exposer exposer("0.0.0.0:9100");
+  exposer.RegisterCollectable(registry.GetCollectable());
+  LOG(INFO) << "Exposing metrics at http://localhost:9100/metrics";
+#endif
+
   proto::MapBuilderServerOptions map_builder_server_options =
       LoadMapBuilderServerOptions(configuration_directory,
                                   configuration_basename);
diff --git a/cartographer_grpc/metrics/prometheus/metrics_test.cc b/cartographer_grpc/metrics/prometheus/metrics_test.cc
index 62dd51d..e1ddacd 100644
--- a/cartographer_grpc/metrics/prometheus/metrics_test.cc
+++ b/cartographer_grpc/metrics/prometheus/metrics_test.cc
@@ -131,6 +131,17 @@ TEST(MetricsTest, CollectHistogram) {
   EXPECT_EQ(collected[0].metric(0).histogram().bucket(0).cumulative_count(), 1);
 }
 
+TEST(MetricsTest, RunExposerServer) {
+  FamilyFactory registry;
+  Algorithm::RegisterMetrics(&registry);
+  cartographer::metrics::RegisterAllMetrics(&registry);
+  ::prometheus::Exposer exposer("0.0.0.0:9100");
+  exposer.RegisterCollectable(registry.GetCollectable());
+
+  Algorithm algorithm;
+  algorithm.Run();
+}
+
 }  // namespace
 }  // namespace prometheus
 }  // namespace metrics