From fdcd7fca10dd00bb724bca7d27125d21d2cb5357 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Fri, 9 Jun 2017 01:00:21 +0200
Subject: [PATCH] Add an exported metrics for number of connected clients.

---
 httpd.cpp | 3 +++
 httpd.h   | 4 ++++
 2 files changed, 7 insertions(+)

diff --git a/httpd.cpp b/httpd.cpp
index e76cc80..2b19779 100644
--- a/httpd.cpp
+++ b/httpd.cpp
@@ -22,6 +22,7 @@ using namespace std;
 
 HTTPD::HTTPD()
 {
+	global_metrics.register_int_metric("num_connected_clients", &metric_num_connected_clients);
 }
 
 HTTPD::~HTTPD()
@@ -94,6 +95,7 @@ int HTTPD::answer_to_connection(MHD_Connection *connection,
 		unique_lock<mutex> lock(streams_mutex);
 		streams.insert(stream);
 	}
+	++metric_num_connected_clients;
 	*con_cls = stream;
 
 	// Does not strictly have to be equal to MUX_BUFFER_SIZE.
@@ -119,6 +121,7 @@ void HTTPD::free_stream(void *cls)
 		delete stream;
 		httpd->streams.erase(stream);
 	}
+	--httpd->metric_num_connected_clients;
 }
 
 ssize_t HTTPD::Stream::reader_callback_thunk(void *cls, uint64_t pos, char *buf, size_t max)
diff --git a/httpd.h b/httpd.h
index 902745a..6e37c52 100644
--- a/httpd.h
+++ b/httpd.h
@@ -6,6 +6,7 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <sys/types.h>
+#include <atomic>
 #include <condition_variable>
 #include <deque>
 #include <mutex>
@@ -78,6 +79,9 @@ private:
 	std::mutex streams_mutex;
 	std::set<Stream *> streams;  // Not owned.
 	std::string header;
+
+	// Metrics.
+	std::atomic<int64_t> metric_num_connected_clients{0};
 };
 
 #endif  // !defined(_HTTPD_H)
-- 
2.39.2