Add Prometheus exporter

lib/api/CMakeLists.txt

@@ -26,6 +26,7 @@ set(API_SRC
     requests/node_stats.cpp
     requests/node_stats_reset.cpp
     requests/node_file.cpp
+    requests/metrics.cpp
     requests/paths.cpp
     requests/path_info.cpp
     requests/path_action.cpp

lib/api/requests/metrics.cpp

@@ -0,0 +1,77 @@
+/* The Prometheus metrics endpoint.
+ *
+ * Author: Youssef Nakti <youssef.nakti@eonerc.rwth-aachen.de>
+ * SPDX-FileCopyrightText: 2025 Institute for Automation of Complex Power Systems, RWTH Aachen University
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <chrono>
+#include <jansson.h>
+#include <villas/api/request.hpp>
+#include <villas/api/response.hpp>
+#include <villas/api/session.hpp>
+#include <villas/node.hpp>
+#include <villas/stats.hpp>
+#include <villas/super_node.hpp>
+#include <villas/utils.hpp>
+
+namespace villas {
+namespace node {
+namespace api {
+
+class MetricsRequest : public Request {
+private:
+  std::unordered_map<Stats::Metric, std::string> metrics_subset = {
+      {Stats::Metric::SMPS_SKIPPED, "skipped"},
+      {Stats::Metric::OWD, "owd"},
+      {Stats::Metric::AGE, "age"},
+      {Stats::Metric::SIGNAL_COUNT, "signalcnt"},
+      {Stats::Metric::RTP_PKTS_LOST, "rtp_pkts_lost"}};
+
+public:
+  using Request::Request;
+
+  virtual Response *execute() {
+    if (method != Session::Method::GET)
+      throw InvalidMethod(this);
+
+    if (body != nullptr)
+      throw BadRequest("Nodes endpoint does not accept any body data");
+
+    std::string text_res = "";
+    NodeList node_list = session->getSuperNode()->getNodes();
+    for (Node *node : node_list) {
+      auto stats = node->getStats();
+      if (!stats)
+        continue;
+      std::string node_name = node->getNameShort();
+      for (auto &metric : metrics_subset) {
+        Hist histogram = stats->getHistogram(metric.first);
+        std::string t = std::to_string(
+            std::chrono::duration_cast<std::chrono::milliseconds>(
+                std::chrono::system_clock::now().time_since_epoch())
+                .count());
+
+        text_res += metric.second + " {node=\"" + node_name +
+                    "\" acc=\"last\"} " + std::to_string(histogram.getLast()) +
+                    " " + t + "\n";
+        text_res += metric.second + " {node=\"" + node_name +
+                    "\" acc=\"total\"} " +
+                    std::to_string(histogram.getTotal()) + " " + t + "\n";
+      }
+    }
+
+    return new Response(session, HTTP_STATUS_OK, "text/plain; charset=UTF-8",
+                        Buffer(text_res.c_str(), text_res.size()));
+  }
+};
+
+// Register API request
+static char n[] = "metrics";
+static char r[] = "/metrics";
+static char d[] = "Get Prometheus metrics from all nodes";
+static RequestPlugin<MetricsRequest, n, r, d> p;
+
+} // namespace api
+} // namespace node
+} // namespace villas

tests/integration/api-metrics.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+#
+# Integration test for remote API
+#
+# Author: Steffen Vogel <post@steffenvogel.de>
+# SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
+# SPDX-License-Identifier: Apache-2.0
+
+set -e
+
+DIR=$(mktemp -d)
+pushd ${DIR}
+
+function finish {
+    popd
+    rm -rf ${DIR}
+}
+trap finish EXIT
+
+cat > config.json <<EOF
+{
+    "http": {
+        "port": 8080
+    },
+    "nodes": {
+        "signal": {
+             "type": "signal",
+             "count": 10,
+             "rate": 10,
+             "signal": "sine"
+        }
+    },
+    "paths": [
+        {
+             "in": "signal",
+             "hooks": [
+                "print"
+             ]
+        }
+    ]
+}
+EOF
+
+# Start VILLASnode instance with local config
+villas node config.json &
+
+# Wait for node to complete init
+sleep 1
+
+# Fetch config via API
+curl -s http://localhost:8080/api/v2/metrics > metrics
+
+# Shutdown VILLASnode
+kill $!
+
+cat metrics