add basic metrics impl

src/main/java/xyz/mcutils/backend/service/MetricService.java

@@ -0,0 +1,121 @@
+package xyz.mcutils.backend.service;
+
+import com.influxdb.client.WriteApiBlocking;
+import com.influxdb.spring.influx.InfluxDB2AutoConfiguration;
+import lombok.extern.log4j.Log4j2;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+import xyz.mcutils.backend.common.Timer;
+import xyz.mcutils.backend.repository.MetricsRepository;
+import xyz.mcutils.backend.service.metric.Metric;
+import xyz.mcutils.backend.service.metric.metrics.RequestsPerRouteMetric;
+import xyz.mcutils.backend.service.metric.metrics.TotalRequestsMetric;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.TimeUnit;
+
+@Service @Log4j2
+public class MetricService {
+    /**
+     * The metrics that are registered.
+     */
+    private final Map<Class<?>, Metric<?>> metrics = new HashMap<>();
+
+    /**
+     * The interval in which the metrics are saved.
+     */
+    private final long saveInterval = TimeUnit.MINUTES.toMillis(1);
+
+    /**
+     * The interval in which the metrics are written to InfluxDB.
+     */
+    private final long writeInfluxInterval = TimeUnit.SECONDS.toMillis(30);
+
+    private final WriteApiBlocking influxWriteApi;
+    private final MetricsRepository metricsRepository;
+
+    @Autowired
+    public MetricService(InfluxDB2AutoConfiguration influxAutoConfiguration, MetricsRepository metricsRepository) {
+        this.influxWriteApi = influxAutoConfiguration.influxDBClient().getWriteApiBlocking();
+        this.metricsRepository = metricsRepository;
+
+        // Register the metrics
+        registerMetric(new TotalRequestsMetric());
+        registerMetric(new RequestsPerRouteMetric());
+
+        // Load the metrics from Redis
+        loadMetrics();
+
+        Timer.scheduleRepeating(this::saveMetrics, saveInterval, saveInterval);
+        Timer.scheduleRepeating(this::writeToInflux, writeInfluxInterval, writeInfluxInterval);
+    }
+
+    /**
+     * Register a metric.
+     *
+     * @param metric the metric to register
+     */
+    public void registerMetric(Metric<?> metric) {
+        if (metrics.containsKey(metric.getClass())) {
+            throw new IllegalArgumentException("A metric with the class " + metric.getClass().getName() + " is already registered");
+        }
+        metrics.put(metric.getClass(), metric);
+    }
+
+    /**
+     * Get a metric by its class.
+     *
+     * @param clazz the class of the metric
+     * @return the metric
+     * @throws IllegalArgumentException if there is no metric with the class registered
+     */
+    public Metric<?> getMetric(Class<?> clazz) throws IllegalArgumentException {
+        if (!metrics.containsKey(clazz)) {
+            throw new IllegalArgumentException("No metric with the class " + clazz.getName() + " is registered");
+        }
+        return metrics.get(clazz);
+    }
+
+    /**
+     * Load all metrics from Redis.
+     */
+    public void loadMetrics() {
+        log.info("Loading metrics");
+        for (Metric<?> metric : metricsRepository.findAll()) {
+            metrics.put(metric.getClass(), metric);
+        }
+        log.info("Loaded {} metrics", metrics.size());
+    }
+
+    /**
+     * Save all metrics to Redis.
+     */
+    private void saveMetrics() {
+        log.info("Saving metrics to Redis");
+        for (Metric<?> metric : metrics.values()) {
+            saveMetric(metric);
+        }
+        log.info("Saved {} metrics", metrics.size());
+    }
+
+    /**
+     * Save a metric to Redis.
+     *
+     * @param metric the metric to save
+     */
+    private void saveMetric(Metric<?> metric) {
+        metricsRepository.save(metric); // Save the metric to the repository
+    }
+
+    /**
+     * Push all metrics to InfluxDB.
+     */
+    private void writeToInflux() {
+        log.info("Writing metrics to InfluxDB");
+        for (Metric<?> metric : metrics.values()) {
+            influxWriteApi.writePoint(metric.toPoint());
+        }
+        log.info("Wrote {} metrics", metrics.size());
+    }
+}