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feat(api): Add a new metrics endpoint for exporting statistics to Prometheus
Co-authored-by: SystemsPurge <naktiyoussef@proton.me> Signed-off-by: SystemsPurge <naktiyoussef@proton.me> Co-authored-by: Steffen Vogel <steffen.vogel@opal-rt.com> Signed-off-by: Steffen Vogel <steffen.vogel@opal-rt.com>
1 parent c9ba515 commit 19b2cea

5 files changed

Lines changed: 273 additions & 7 deletions

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‎common/include/villas/hist.hpp‎

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@@ -7,6 +7,7 @@
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#pragma once
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#include <string>
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#include <vector>
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#include <jansson.h>
@@ -60,6 +61,9 @@ class Hist {
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// Write the histogram in JSON format to file \p f.
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int dumpJson(FILE *f) const;
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std::string toPrometheusText(const std::string &metric_name,
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const std::string &node_name) const;
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// Build a libjansson / JSON object of the histogram.
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json_t *toJson() const;
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‎common/lib/hist.cpp‎

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@@ -37,13 +37,16 @@ void Hist::put(double value) {
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if (data.size()) {
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if (total < warmup) {
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// We are still in warmup phase... Waiting for more samples...
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} else if (data.size() && total == warmup && warmup != 0) {
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low = getMean() - 3 * getStddev();
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high = getMean() + 3 * getStddev();
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} else if (total == warmup) {
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if (warmup != 0) {
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low = getMean() - 3 * getStddev();
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high = getMean() + 3 * getStddev();
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} else {
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low = -10;
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high = 10;
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}
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resolution = (high - low) / data.size();
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} else if (data.size() && (total == warmup) && (warmup == 0)) {
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// There is no warmup phase
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// TODO resolution = ?
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} else {
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idx_t idx = std::round((value - low) / resolution);
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@@ -136,7 +139,7 @@ void Hist::plot(Logger logger) const {
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table.header();
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for (size_t i = 0; i < data.size(); i++) {
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double value = low + (i)*resolution;
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double value = low + (double)i * resolution;
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Hist::cnt_t cnt = data[i];
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int bar = cols[2].getWidth() * ((double)cnt / max);
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@@ -150,6 +153,36 @@ void Hist::plot(Logger logger) const {
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}
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}
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std::string Hist::toPrometheusText(const std::string &metric_name,
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const std::string &node_name) const {
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std::stringstream base;
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base << "#TYPE HISTOGRAM " << metric_name;
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// Needed because Prometheus understands quantiles.
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cnt_t cumsum = 0;
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for (size_t i = 0; i < data.size(); i++) {
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double value = low + ((double)i + 0.5) * resolution;
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if (cumsum <= UINTMAX_MAX - data[i]) {
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cumsum += data[i];
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} else {
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cumsum = UINTMAX_MAX; // Avoid overflow
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}
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base << "\n"
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<< metric_name << " {node=\"" << node_name << "\" le=\"" << value
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<< "\"} " << cumsum;
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}
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base << "\n"
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<< metric_name << " {node=\"" << node_name << "\" le=\"+Inf\"} " << total
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<< "\n"
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<< metric_name << "_count "
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<< " {node=\"" << node_name << "\"} " << total;
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return base.str();
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}
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char *Hist::dump() const {
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char *buf = new char[128];
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if (!buf)

‎lib/api/CMakeLists.txt‎

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

‎lib/api/requests/metrics.cpp‎

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@@ -0,0 +1,70 @@
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/* The metrics API ressource.
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*
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* Author: Steffen Vogel <post@steffenvogel.de>
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* Author: Youssef Nakti <naktiyoussef@proton.me>
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* SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
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* SPDX-License-Identifier: Apache-2.0
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*/
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#include <chrono>
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#include <jansson.h>
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#include <villas/api/request.hpp>
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#include <villas/api/response.hpp>
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#include <villas/api/session.hpp>
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#include <villas/node.hpp>
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#include <villas/stats.hpp>
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#include <villas/super_node.hpp>
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#include <villas/utils.hpp>
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namespace villas {
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namespace node {
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namespace api {
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class MetricsRequest : public Request {
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public:
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using Request::Request;
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virtual Response *execute() {
30+
if (method != Session::Method::GET) {
31+
throw InvalidMethod(this);
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}
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if (body != nullptr) {
35+
throw BadRequest("The metrics endpoint does not accept any body data");
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}
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std::stringstream ss;
39+
NodeList node_list = session->getSuperNode()->getNodes();
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for (Node *node : node_list) {
42+
auto stats = node->getStats();
43+
if (!stats)
44+
continue;
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46+
std::string node_name = node->getNameShort();
47+
for (auto &metric : Stats::metrics) {
48+
std::string metric_name = metric.second.name;
49+
std::replace(metric_name.begin(), metric_name.end(), '.', '_');
50+
ss << stats->getHistogram(metric.first)
51+
.toPrometheusText(metric_name, node->getNameShort())
52+
<< "\n\n";
53+
}
54+
}
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56+
auto str = ss.str();
57+
return new Response(session, HTTP_STATUS_OK, "text/plain; charset=UTF-8",
58+
Buffer(str.c_str(), str.size()));
59+
}
60+
};
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// Register API request
63+
static char n[] = "metrics";
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static char r[] = "/metrics";
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static char d[] = "Get stats of all nodes in Prometheus metrics format";
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static RequestPlugin<MetricsRequest, n, r, d> p;
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} // namespace api
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} // namespace node
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} // namespace villas

‎tests/integration/api-metrics.sh‎

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#!/usr/bin/env bash
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#
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# Integration test for remote API
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#
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# Author: Steffen Vogel <steffen.vogel@opal-rt.com>
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# SPDX-FileCopyrightText: 2025 OPAL-RT Germany GmbH
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# SPDX-License-Identifier: Apache-2.0
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9+
set -e
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DIR=$(mktemp -d)
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pushd ${DIR}
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function finish {
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popd
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rm -rf ${DIR}
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}
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trap finish EXIT
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cat > config.json <<EOF
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{
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"http": {
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"port": 8080
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},
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"nodes": {
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"node1": {
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"type": "signal",
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"signal": "sine",
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"limit": 10,
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"values": 1,
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33+
"in": {
34+
"hooks": [
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{
36+
"type": "stats",
37+
"warmup": 0,
38+
"buckets": 5
39+
}
40+
]
41+
}
42+
}
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},
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"paths": [
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{
46+
"in": "node1"
47+
}
48+
]
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}
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EOF
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cat <<EOF > expected
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#TYPE HISTOGRAM rtp_jitter
54+
rtp_jitter {node="node1" le="0"} 0
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rtp_jitter {node="node1" le="0"} 0
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rtp_jitter {node="node1" le="0"} 0
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rtp_jitter {node="node1" le="0"} 0
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rtp_jitter {node="node1" le="0"} 0
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rtp_jitter {node="node1" le="+Inf"} 0
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rtp_jitter_count {node="node1"} 0
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#TYPE HISTOGRAM rtp_pkts_lost
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rtp_pkts_lost {node="node1" le="0"} 0
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rtp_pkts_lost {node="node1" le="0"} 0
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rtp_pkts_lost {node="node1" le="0"} 0
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rtp_pkts_lost {node="node1" le="0"} 0
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rtp_pkts_lost {node="node1" le="0"} 0
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rtp_pkts_lost {node="node1" le="+Inf"} 0
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rtp_pkts_lost_count {node="node1"} 0
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71+
#TYPE HISTOGRAM rtp_loss_fraction
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rtp_loss_fraction {node="node1" le="0"} 0
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rtp_loss_fraction {node="node1" le="0"} 0
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rtp_loss_fraction {node="node1" le="0"} 0
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rtp_loss_fraction {node="node1" le="0"} 0
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rtp_loss_fraction {node="node1" le="0"} 0
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rtp_loss_fraction {node="node1" le="+Inf"} 0
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rtp_loss_fraction_count {node="node1"} 0
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80+
#TYPE HISTOGRAM signal_cnt
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signal_cnt {node="node1" le="-8"} 0
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signal_cnt {node="node1" le="-4"} 0
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signal_cnt {node="node1" le="0"} 0
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signal_cnt {node="node1" le="4"} 9
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signal_cnt {node="node1" le="8"} 9
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signal_cnt {node="node1" le="+Inf"} 10
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signal_cnt_count {node="node1"} 10
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#TYPE HISTOGRAM age
90+
age {node="node1" le="0"} 0
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age {node="node1" le="0"} 0
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age {node="node1" le="0"} 0
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age {node="node1" le="0"} 0
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age {node="node1" le="0"} 0
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age {node="node1" le="+Inf"} 0
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age_count {node="node1"} 0
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98+
#TYPE HISTOGRAM owd
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owd {node="node1" le="-8"} 0
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owd {node="node1" le="-4"} 0
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owd {node="node1" le="0"} 0
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owd {node="node1" le="4"} 8
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owd {node="node1" le="8"} 8
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owd {node="node1" le="+Inf"} 9
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owd_count {node="node1"} 9
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107+
#TYPE HISTOGRAM gap_received
108+
gap_received {node="node1" le="-8"} 0
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gap_received {node="node1" le="-4"} 0
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gap_received {node="node1" le="0"} 0
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gap_received {node="node1" le="4"} 8
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gap_received {node="node1" le="8"} 8
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gap_received {node="node1" le="+Inf"} 9
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gap_received_count {node="node1"} 9
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#TYPE HISTOGRAM gap_sent
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gap_sent {node="node1" le="-8"} 0
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gap_sent {node="node1" le="-4"} 0
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gap_sent {node="node1" le="0"} 0
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gap_sent {node="node1" le="4"} 8
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gap_sent {node="node1" le="8"} 8
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gap_sent {node="node1" le="+Inf"} 9
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gap_sent_count {node="node1"} 9
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#TYPE HISTOGRAM reordered
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reordered {node="node1" le="0"} 0
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reordered {node="node1" le="0"} 0
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reordered {node="node1" le="0"} 0
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reordered {node="node1" le="0"} 0
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reordered {node="node1" le="0"} 0
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reordered {node="node1" le="+Inf"} 0
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reordered_count {node="node1"} 0
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#TYPE HISTOGRAM skipped
135+
skipped {node="node1" le="0"} 0
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skipped {node="node1" le="0"} 0
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skipped {node="node1" le="0"} 0
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skipped {node="node1" le="0"} 0
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skipped {node="node1" le="0"} 0
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skipped {node="node1" le="+Inf"} 0
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skipped_count {node="node1"} 0
142+
143+
EOF
144+
145+
# Start VILLASnode instance with local config
146+
villas node config.json &
147+
148+
# Wait for node to complete init
149+
sleep 2
150+
151+
# Fetch config via API
152+
curl -s http://localhost:8080/api/v2/metrics > metrics
153+
154+
# Shutdown VILLASnode
155+
kill $!
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157+
# Check if metrics contain expected values
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diff -u expected metrics

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