feat(prometheus): add helper builders for custom metrics

examples/example_logit_prometheus_server.cpp

@@ -1,5 +1,9 @@
 #include <logit.hpp>
 
+#ifdef LOGIT_WITH_PROMETHEUS_SERVER
+#include <logit/loggers/prometheus/PrometheusMetricBuilders.hpp>
+#endif
+
 int main() {
 #ifndef LOGIT_WITH_PROMETHEUS_SERVER
     LOGIT_ADD_CONSOLE_DEFAULT();
@@ -15,15 +19,11 @@ int main() {
 
     // Optional: add custom metrics on each scrape
     config.on_collect = [](std::vector<logit::PrometheusMetricFamily>& families) {
-        logit::PrometheusMetricFamily mf;
-        mf.name = "myapp_uptime_seconds";
-        mf.help = "Application uptime in seconds";
-        mf.type = logit::PrometheusMetricType::Gauge;
-        logit::PrometheusSample s;
-        s.name = "myapp_uptime_seconds";
-        s.value = 42.0;
-        mf.samples.push_back(s);
-        families.push_back(mf);
+        logit::add_prometheus_gauge(
+            families,
+            "myapp_uptime_seconds",
+            "Application uptime in seconds",
+            42.0);
     };
 
     LOGIT_ADD_LOGGER(

include/logit_cpp/logit/loggers/prometheus/PrometheusMetricBuilders.hpp

@@ -0,0 +1,153 @@
+#pragma once
+#ifndef _LOGIT_PROMETHEUS_METRIC_BUILDERS_HPP_INCLUDED
+#define _LOGIT_PROMETHEUS_METRIC_BUILDERS_HPP_INCLUDED
+
+/// \file PrometheusMetricBuilders.hpp
+/// \brief Convenience helpers for constructing Prometheus metric families and samples.
+
+#include "PrometheusTextFormatConfig.hpp"
+
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace logit {
+
+    /// \brief Create a single label pair.
+    inline PrometheusLabel make_prometheus_label(
+        const std::string& name,
+        const std::string& value) {
+        PrometheusLabel label;
+        label.name = name;
+        label.value = value;
+        return label;
+    }
+
+    /// \brief Create a sample for a Prometheus metric family.
+    inline PrometheusSample make_prometheus_sample(
+        const std::string& name,
+        double value,
+        std::vector<PrometheusLabel> labels = {},
+        int64_t timestamp_ms = 0) {
+        PrometheusSample s;
+        s.name = name;
+        s.value = value;
+        s.labels = std::move(labels);
+        s.timestamp_ms = timestamp_ms;
+        return s;
+    }
+
+    /// \brief Create a Counter metric family with one unlabeled sample.
+    inline PrometheusMetricFamily make_prometheus_counter(
+        const std::string& name,
+        const std::string& help,
+        double value) {
+        PrometheusMetricFamily mf;
+        mf.name = name;
+        mf.help = help;
+        mf.type = PrometheusMetricType::Counter;
+        mf.samples.push_back(make_prometheus_sample(name, value));
+        return mf;
+    }
+
+    /// \brief Create a Counter metric family with one labeled sample.
+    inline PrometheusMetricFamily make_prometheus_counter(
+        const std::string& name,
+        const std::string& help,
+        double value,
+        std::vector<PrometheusLabel> labels) {
+        PrometheusMetricFamily mf;
+        mf.name = name;
+        mf.help = help;
+        mf.type = PrometheusMetricType::Counter;
+        mf.samples.push_back(make_prometheus_sample(name, value, std::move(labels)));
+        return mf;
+    }
+
+    /// \brief Create a Gauge metric family with one unlabeled sample.
+    inline PrometheusMetricFamily make_prometheus_gauge(
+        const std::string& name,
+        const std::string& help,
+        double value) {
+        PrometheusMetricFamily mf;
+        mf.name = name;
+        mf.help = help;
+        mf.type = PrometheusMetricType::Gauge;
+        mf.samples.push_back(make_prometheus_sample(name, value));
+        return mf;
+    }
+
+    /// \brief Create a Gauge metric family with one labeled sample.
+    inline PrometheusMetricFamily make_prometheus_gauge(
+        const std::string& name,
+        const std::string& help,
+        double value,
+        std::vector<PrometheusLabel> labels) {
+        PrometheusMetricFamily mf;
+        mf.name = name;
+        mf.help = help;
+        mf.type = PrometheusMetricType::Gauge;
+        mf.samples.push_back(make_prometheus_sample(name, value, std::move(labels)));
+        return mf;
+    }
+
+    /// \brief Create an Untyped metric family with one unlabeled sample.
+    inline PrometheusMetricFamily make_prometheus_untyped(
+        const std::string& name,
+        const std::string& help,
+        double value) {
+        PrometheusMetricFamily mf;
+        mf.name = name;
+        mf.help = help;
+        mf.type = PrometheusMetricType::Untyped;
+        mf.samples.push_back(make_prometheus_sample(name, value));
+        return mf;
+    }
+
+    /// \brief Create an Untyped metric family with one labeled sample.
+    inline PrometheusMetricFamily make_prometheus_untyped(
+        const std::string& name,
+        const std::string& help,
+        double value,
+        std::vector<PrometheusLabel> labels) {
+        PrometheusMetricFamily mf;
+        mf.name = name;
+        mf.help = help;
+        mf.type = PrometheusMetricType::Untyped;
+        mf.samples.push_back(make_prometheus_sample(name, value, std::move(labels)));
+        return mf;
+    }
+
+    /// \brief Append a Counter metric family to the families vector (convenience for on_collect).
+    inline void add_prometheus_counter(
+        std::vector<PrometheusMetricFamily>& families,
+        const std::string& name,
+        const std::string& help,
+        double value,
+        std::vector<PrometheusLabel> labels = {}) {
+        families.push_back(make_prometheus_counter(name, help, value, std::move(labels)));
+    }
+
+    /// \brief Append a Gauge metric family to the families vector (convenience for on_collect).
+    inline void add_prometheus_gauge(
+        std::vector<PrometheusMetricFamily>& families,
+        const std::string& name,
+        const std::string& help,
+        double value,
+        std::vector<PrometheusLabel> labels = {}) {
+        families.push_back(make_prometheus_gauge(name, help, value, std::move(labels)));
+    }
+
+    /// \brief Append an Untyped metric family to the families vector (convenience for on_collect).
+    inline void add_prometheus_untyped(
+        std::vector<PrometheusMetricFamily>& families,
+        const std::string& name,
+        const std::string& help,
+        double value,
+        std::vector<PrometheusLabel> labels = {}) {
+        families.push_back(make_prometheus_untyped(name, help, value, std::move(labels)));
+    }
+
+} // namespace logit
+
+#endif // _LOGIT_PROMETHEUS_METRIC_BUILDERS_HPP_INCLUDED

tests/CMakeLists.txt

@@ -57,6 +57,7 @@ else()
         prometheus_text_serializer_test.cpp
         prometheus_payload_logger_test.cpp
         prometheus_http_server_logger_test.cpp
+        prometheus_metric_builders_test.cpp
         per_logger_isolation_test.cpp
         per_logger_mixed_mode_test.cpp
         printf_format_macros_test.cpp
@@ -92,6 +93,7 @@ else()
         list(REMOVE_ITEM TEST_SOURCES prometheus_text_serializer_test.cpp)
         list(REMOVE_ITEM TEST_SOURCES prometheus_payload_logger_test.cpp)
         list(REMOVE_ITEM TEST_SOURCES prometheus_http_server_logger_test.cpp)
+        list(REMOVE_ITEM TEST_SOURCES prometheus_metric_builders_test.cpp)
     endif()
     if(LOGIT_WITH_PROMETHEUS AND NOT LOGIT_WITH_PROMETHEUS_SERVER)
         list(REMOVE_ITEM TEST_SOURCES prometheus_http_server_logger_test.cpp)

tests/prometheus_http_server_logger_test.cpp

@@ -1,5 +1,6 @@
 #include <logit/utils.hpp>
 #include <logit/loggers/PrometheusHttpServerLogger.hpp>
+#include <logit/loggers/prometheus/PrometheusMetricBuilders.hpp>
 
 #if defined(LOGIT_WITH_PROMETHEUS_SERVER)
 
@@ -93,15 +94,7 @@ int main() {
         logit::PrometheusHttpServerLogger::Config config;
         config.port = 43194;
         config.on_collect = [](std::vector<logit::PrometheusMetricFamily>& families) {
-            logit::PrometheusMetricFamily mf;
-            mf.name = "custom_metric";
-            mf.help = "A custom metric";
-            mf.type = logit::PrometheusMetricType::Gauge;
-            logit::PrometheusSample s;
-            s.name = "custom_metric";
-            s.value = 77.0;
-            mf.samples.push_back(s);
-            families.push_back(mf);
+            logit::add_prometheus_gauge(families, "custom_metric", "A custom metric", 77.0);
         };
         config.start_immediately = false;
 

tests/prometheus_metric_builders_test.cpp

@@ -0,0 +1,120 @@
+#include <logit/loggers/prometheus/PrometheusMetricBuilders.hpp>
+
+#ifdef LOGIT_WITH_PROMETHEUS
+
+#include <cassert>
+#include <vector>
+
+int main() {
+    // Test 1: make_prometheus_label
+    {
+        auto label = logit::make_prometheus_label("env", "production");
+        assert(label.name == "env");
+        assert(label.value == "production");
+    }
+
+    // Test 2: make_prometheus_sample (unlabeled)
+    {
+        auto sample = logit::make_prometheus_sample("cpu_seconds_total", 123.45);
+        assert(sample.name == "cpu_seconds_total");
+        assert(sample.value == 123.45);
+        assert(sample.labels.empty());
+        assert(sample.timestamp_ms == 0);
+    }
+
+    // Test 3: make_prometheus_sample (with labels and timestamp)
+    {
+        auto sample = logit::make_prometheus_sample(
+            "cpu_seconds_total", 67.89,
+            {logit::make_prometheus_label("cpu", "0")},
+            1710000000123LL);
+        assert(sample.name == "cpu_seconds_total");
+        assert(sample.value == 67.89);
+        assert(sample.labels.size() == 1);
+        assert(sample.labels[0].name == "cpu");
+        assert(sample.labels[0].value == "0");
+        assert(sample.timestamp_ms == 1710000000123LL);
+    }
+
+    // Test 4: make_prometheus_counter (unlabeled)
+    {
+        auto mf = logit::make_prometheus_counter("requests_total", "Total requests", 42.0);
+        assert(mf.name == "requests_total");
+        assert(mf.help == "Total requests");
+        assert(mf.type == logit::PrometheusMetricType::Counter);
+        assert(mf.samples.size() == 1);
+        assert(mf.samples[0].name == "requests_total");
+        assert(mf.samples[0].value == 42.0);
+        assert(mf.samples[0].labels.empty());
+    }
+
+    // Test 5: make_prometheus_counter (labeled)
+    {
+        auto mf = logit::make_prometheus_counter(
+            "requests_total", "Total requests", 7.0,
+            {logit::make_prometheus_label("method", "GET")});
+        assert(mf.samples[0].labels.size() == 1);
+        assert(mf.samples[0].labels[0].name == "method");
+        assert(mf.samples[0].labels[0].value == "GET");
+    }
+
+    // Test 6: make_prometheus_gauge (unlabeled)
+    {
+        auto mf = logit::make_prometheus_gauge("queue_size", "Current queue size", 3.0);
+        assert(mf.name == "queue_size");
+        assert(mf.help == "Current queue size");
+        assert(mf.type == logit::PrometheusMetricType::Gauge);
+        assert(mf.samples[0].value == 3.0);
+    }
+
+    // Test 7: make_prometheus_gauge (labeled)
+    {
+        auto mf = logit::make_prometheus_gauge(
+            "temperature_celsius", "Room temperature", 22.5,
+            {logit::make_prometheus_label("room", "server_room_a")});
+        assert(mf.type == logit::PrometheusMetricType::Gauge);
+        assert(mf.samples[0].labels[0].value == "server_room_a");
+    }
+
+    // Test 8: make_prometheus_untyped (unlabeled)
+    {
+        auto mf = logit::make_prometheus_untyped("raw_value", "Some raw value", 99.0);
+        assert(mf.name == "raw_value");
+        assert(mf.type == logit::PrometheusMetricType::Untyped);
+        assert(mf.samples[0].value == 99.0);
+    }
+
+    // Test 9: add_prometheus_counter via vector
+    {
+        std::vector<logit::PrometheusMetricFamily> families;
+        logit::add_prometheus_counter(families, "errors_total", "Total errors", 5.0);
+        assert(families.size() == 1);
+        assert(families[0].name == "errors_total");
+        assert(families[0].type == logit::PrometheusMetricType::Counter);
+
+        logit::add_prometheus_gauge(
+            families, "active_sessions", "Active sessions", 12.0,
+            {logit::make_prometheus_label("region", "eu-west")});
+        assert(families.size() == 2);
+        assert(families[1].name == "active_sessions");
+        assert(families[1].samples[0].labels[0].value == "eu-west");
+    }
+
+    // Test 10: add_prometheus_untyped via vector
+    {
+        std::vector<logit::PrometheusMetricFamily> families;
+        logit::add_prometheus_untyped(families, "misc", "Misc value", 0.0);
+        assert(families.size() == 1);
+        assert(families[0].type == logit::PrometheusMetricType::Untyped);
+    }
+
+    return 0;
+}
+
+#else
+
+int main() {
+    return 0;
+}
+
+#endif

tests/prometheus_payload_logger_test.cpp

@@ -1,5 +1,6 @@
 #include <logit/utils.hpp>
 #include <logit/loggers/PrometheusPayloadLogger.hpp>
+#include <logit/loggers/prometheus/PrometheusMetricBuilders.hpp>
 
 #ifdef LOGIT_WITH_PROMETHEUS
 
@@ -111,15 +112,7 @@ int main() {
     {
         logit::PrometheusPayloadLogger::Config config;
         config.on_collect = [](std::vector<logit::PrometheusMetricFamily>& families) {
-            logit::PrometheusMetricFamily mf;
-            mf.name = "custom_metric";
-            mf.help = "A custom metric";
-            mf.type = logit::PrometheusMetricType::Gauge;
-            logit::PrometheusSample s;
-            s.name = "custom_metric";
-            s.value = 99.0;
-            mf.samples.push_back(s);
-            families.push_back(mf);
+            logit::add_prometheus_gauge(families, "custom_metric", "A custom metric", 99.0);
         };
 
         auto logger = std::unique_ptr<logit::PrometheusPayloadLogger>(new logit::PrometheusPayloadLogger(config));