feat: testing metrics

src/main/java/com/restcountries/log/MetricsLogger.java

@@ -0,0 +1,113 @@
+package com.restcountries.log;
+
+import io.micronaut.scheduling.annotation.Scheduled;
+import jakarta.inject.Singleton;
+
+import java.io.File;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.time.LocalDate;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.concurrent.atomic.AtomicLong;
+
+@Singleton
+public class MetricsLogger {
+
+    private final RequestCounter counter;
+    private final AtomicLong globalCounter = new AtomicLong(0);
+
+    private final AtomicLong dailyCounter = new AtomicLong(0);
+    private LocalDate currentDay = LocalDate.now();
+
+    public MetricsLogger(RequestCounter counter) {
+        this.counter = counter;
+    }
+
+    @Scheduled(fixedRate = "6h")
+    void logStats() {
+        long requests = counter.getTotalRequests();
+
+        if (requests == 0) {
+            return;
+        }
+
+        long totalRequests = globalCounter.addAndGet(requests);
+        dailyCounter.addAndGet(requests);
+
+        int windowMinutes = 360;
+        double avgRps = requests / (windowMinutes * 60.0);
+
+        LocalDateTime now = LocalDateTime.now();
+
+        writeLine(
+                now,
+                windowMinutes,
+                requests,
+                totalRequests,
+                avgRps,
+                ""
+        );
+
+        counter.reset();
+
+        checkDailySummary(now);
+    }
+
+    private void checkDailySummary(LocalDateTime now) {
+        LocalDate today = now.toLocalDate();
+
+        if (!today.equals(currentDay)) {
+            writeDailySummary();
+            dailyCounter.set(0);
+            currentDay = today;
+        }
+    }
+
+    private void writeDailySummary() {
+        long dailyTotal = dailyCounter.get();
+
+        double avgRps = dailyTotal / 86400.0; // 24h
+
+        LocalDateTime endOfDay = currentDay.atTime(23, 59, 59);
+
+        writeLine(
+                endOfDay,
+                1440,
+                dailyTotal,
+                null,
+                avgRps,
+                "DAILY_SUMMARY"
+        );
+    }
+
+    private void writeLine(
+            LocalDateTime timestamp,
+            int windowMinutes,
+            Long requests,
+            Long totalRequests,
+            double avgRps,
+            String notes
+    ) {
+        String line = String.join(",",
+                timestamp.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss")),
+                String.valueOf(windowMinutes),
+                String.valueOf(requests),
+                totalRequests != null ? String.valueOf(totalRequests) : "",
+                String.format("%.2f", avgRps),
+                notes
+        ) + "\n";
+
+        File file = new File("/tmp/request-stats.csv");
+        boolean writeHeader = !file.exists();
+
+        try (FileWriter fw = new FileWriter(file, true)) {
+            if (writeHeader) {
+                fw.write("timestamp,window_minutes,requests,total_requests,avg_rps,notes\n");
+            }
+            fw.write(line);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}

src/main/java/com/restcountries/log/RequestCounter.java

@@ -0,0 +1,43 @@
+package com.restcountries.log;
+
+import jakarta.inject.Singleton;
+
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicLong;
+
+@Singleton
+public class RequestCounter {
+
+    private final AtomicLong totalRequests = new AtomicLong(0);
+    private final ConcurrentHashMap<String, AtomicLong> endpointCounts = new ConcurrentHashMap<>();
+
+    public void increment(String path) {
+        totalRequests.incrementAndGet();
+        endpointCounts
+                .computeIfAbsent(path, k -> new AtomicLong(0))
+                .incrementAndGet();
+    }
+
+    public long getTotalRequests() {
+        return totalRequests.get();
+    }
+
+    public ConcurrentHashMap<String, AtomicLong> getEndpointCounts() {
+        return endpointCounts;
+    }
+
+    public List<Map.Entry<String, Long>> getTopEndpoints() {
+        return endpointCounts.entrySet()
+                .stream()
+                .map(e -> Map.entry(e.getKey(), e.getValue().get()))
+                .sorted((a, b) -> Long.compare(b.getValue(), a.getValue())) // DESC
+                .toList();
+    }
+
+    public void reset() {
+        totalRequests.set(0);
+        endpointCounts.clear();
+    }
+}

src/main/java/com/restcountries/log/RequestLoggingFilter.java

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+package com.restcountries.log;
+
+import io.micronaut.http.HttpRequest;
+import io.micronaut.http.MutableHttpResponse;
+import io.micronaut.http.annotation.Filter;
+import io.micronaut.http.filter.HttpServerFilter;
+import io.micronaut.http.filter.ServerFilterChain;
+import jakarta.inject.Inject;
+import org.reactivestreams.Publisher;
+
+@Filter("/**")
+public class RequestLoggingFilter implements HttpServerFilter {
+
+    @Inject
+    RequestCounter counter;
+
+    @Override
+    public Publisher<MutableHttpResponse<?>> doFilter(HttpRequest<?> request, ServerFilterChain chain) {
+        counter.increment(request.getPath());
+        return chain.proceed(request);
+    }
+}