modules: Add preliminary prometheus metrics endpoint.

modules/Makefile.am

@@ -58,12 +58,14 @@ webroot_la_SOURCES = webroot.cc
 webhook_la_SOURCES = webhook.cc
 console_la_SOURCES = console.cc
 vm_la_SOURCES = vm.cc
+metrics_la_SOURCES = metrics.cc
 
 module_LTLIBRARIES = \
 	webroot.la \
 	webhook.la \
 	console.la \
 	vm.la \
+	metrics.la \
 	###
 
 ###############################################################################

modules/metrics.cc

@@ -0,0 +1,75 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+using namespace ircd;
+
+mapi::header
+IRCD_MODULE
+{
+	"Prometheus Metrics"
+};
+
+resource
+metrics_resource
+{
+	"/metrics",
+	{
+		"Prometheus Metrics"
+	}
+};
+
+static resource::response
+get__metrics(client &,
+             const resource::request &);
+
+resource::method
+metrics_get
+{
+	metrics_resource, "GET", get__metrics
+};
+
+resource::response
+get__metrics(client &client,
+             const resource::request &request)
+{
+	static const size_t buf_max
+	{
+		4096
+	};
+
+	char buf[buf_max];
+	std::stringstream out;
+	pubsetbuf(out, buf);
+
+	const time_t ts
+	{
+		ircd::time<milliseconds>()
+	};
+
+	out << "aio_requests_total"
+	    << ' ' << fs::aio::stats.requests
+	    << ' ' << ts
+	    << '\n';
+
+	out << "aio_requests_bytes_total"
+	    << ' ' << fs::aio::stats.bytes_requests
+	    << ' ' << ts
+	    << '\n';
+
+	const string_view output
+	{
+		view(out, buf)
+	};
+
+	return resource::response
+	{
+		client, output, "text/plain", http::OK
+	};
+}