# Spring Boot Actuator: Monitoring Produksi dengan Micrometer dan Prometheus

> Panduan lengkap Spring Boot Actuator untuk monitoring produksi. Konfigurasi Micrometer, metrik Prometheus, endpoint kustom, dan alerting.

- Published: 2026-03-24
- Updated: 2026-05-04
- Author: SharpSkill
- Tags: spring boot actuator, micrometer, prometheus, monitoring, observability
- Reading time: 16 min

---

Spring Boot Actuator mengubah cara aplikasi Java dimonitor dengan menyediakan endpoint siap produksi untuk health check, metrik, dan diagnostik. Dipadukan dengan Micrometer dan Prometheus, perangkat ini membentuk solusi observability lengkap untuk lingkungan produksi.

> **Poin Kunci**
>
> Actuator secara otomatis menyajikan lebih dari 50 metrik JVM dan aplikasi tanpa konfigurasi tambahan. Micrometer berperan sebagai facade untuk mempublikasikan metrik tersebut ke Prometheus, Grafana, Datadog, atau sistem monitoring lainnya.

## Konfigurasi Dasar dengan Spring Boot 3

### Dependensi Maven yang Diperlukan

Integrasi Actuator dengan Prometheus membutuhkan tiga dependensi utama. Starter Actuator mengaktifkan endpoint, Micrometer menyediakan abstraksi metrik, dan registry Prometheus memformat data untuk scraping.

```xml
<!-- pom.xml -->
<!-- Actuator + Micrometer + Prometheus Configuration -->
<dependencies>
    <!-- Spring Boot Actuator - monitoring endpoints -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>

    <!-- Micrometer Registry Prometheus -->
    <!-- Exposes metrics in Prometheus format -->
    <dependency>
        <groupId>io.micrometer</groupId>
        <artifactId>micrometer-registry-prometheus</artifactId>
    </dependency>

    <!-- AOP for @Timed and @Counted metrics -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-aop</artifactId>
    </dependency>
</dependencies>
```

Dependensi tersebut sudah cukup untuk menyediakan endpoint `/actuator/prometheus` yang dapat di-scrape Prometheus secara berkala.

### Konfigurasi Endpoint Actuator

Secara default hanya endpoint `health` dan `info` yang diekspos via HTTP. Konfigurasi eksplisit menentukan endpoint mana yang tetap dapat diakses di produksi.

```yaml
# application.yml
# Actuator configuration for production
management:
  endpoints:
    web:
      exposure:
        # Endpoints exposed over HTTP
        # health, info, prometheus are minimum for monitoring
        include: health,info,prometheus,metrics,env,loggers
      base-path: /actuator
    # Disable unused endpoints to reduce attack surface
    enabled-by-default: false
  endpoint:
    # Enable each required endpoint individually
    health:
      enabled: true
      show-details: when-authorized
      show-components: when-authorized
    info:
      enabled: true
    prometheus:
      enabled: true
    metrics:
      enabled: true
    env:
      enabled: true
      # Mask sensitive values
      show-values: when-authorized
    loggers:
      enabled: true
```

Opsi `show-details: when-authorized` menampilkan detail kesehatan hanya kepada pengguna terautentikasi dengan peran yang sesuai.

```java
// ActuatorSecurityConfig.java
// Securing Actuator endpoints
package com.example.monitoring.config;

import org.springframework.boot.actuate.autoconfigure.security.servlet.EndpointRequest;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.web.SecurityFilterChain;

@Configuration
public class ActuatorSecurityConfig {

    @Bean
    SecurityFilterChain actuatorSecurityFilterChain(HttpSecurity http) throws Exception {
        return http
            .securityMatcher(EndpointRequest.toAnyEndpoint())
            .authorizeHttpRequests(auth -> auth
                // Health and info public for load balancers
                .requestMatchers(EndpointRequest.to("health", "info")).permitAll()
                // Prometheus accessible from internal network
                .requestMatchers(EndpointRequest.to("prometheus")).hasIpAddress("10.0.0.0/8")
                // Other endpoints restricted to admins
                .anyRequest().hasRole("ACTUATOR_ADMIN")
            )
            .httpBasic(basic -> {})
            .build();
    }
}
```

Konfigurasi ini memberikan akses publik ke endpoint dasar sekaligus melindungi endpoint sensitif.

## Metrik Kustom dengan Micrometer

### Counter dan Gauge Aplikatif

Micrometer menyediakan beberapa tipe metrik yang sesuai dengan kasus penggunaan berbeda. Counter mengukur peristiwa kumulatif, gauge mengukur nilai sesaat, dan timer mengukur durasi sebuah operasi.

```java
// OrderMetricsService.java
// Custom business metrics service
package com.example.monitoring.metrics;

import io.micrometer.core.instrument.Counter;
import io.micrometer.core.instrument.Gauge;
import io.micrometer.core.instrument.MeterRegistry;
import io.micrometer.core.instrument.Timer;
import org.springframework.stereotype.Service;

import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Supplier;

@Service
public class OrderMetricsService {

    // Counter for orders created with status tag
    private final Counter ordersCreatedCounter;
    // Timer to measure processing duration
    private final Timer orderProcessingTimer;
    // Atomic value for pending orders gauge
    private final AtomicInteger pendingOrdersCount = new AtomicInteger(0);

    public OrderMetricsService(MeterRegistry registry) {
        // Counter with tags for filtering in Prometheus
        this.ordersCreatedCounter = Counter.builder("orders.created.total")
            .description("Total number of orders created")
            .tag("application", "order-service")
            .register(registry);

        // Timer with histogram for percentiles
        this.orderProcessingTimer = Timer.builder("orders.processing.duration")
            .description("Order processing duration")
            .publishPercentiles(0.5, 0.95, 0.99)
            .publishPercentileHistogram()
            .register(registry);

        // Gauge linked to atomic value
        // Updates automatically on each scrape
        Gauge.builder("orders.pending.count", pendingOrdersCount, AtomicInteger::get)
            .description("Number of orders pending processing")
            .register(registry);
    }

    public void recordOrderCreated() {
        ordersCreatedCounter.increment();
        pendingOrdersCount.incrementAndGet();
    }

    public void recordOrderProcessed(Runnable processingLogic) {
        // Automatically measures execution duration
        orderProcessingTimer.record(processingLogic);
        pendingOrdersCount.decrementAndGet();
    }

    public <T> T recordOrderProcessedWithResult(Supplier<T> processingLogic) {
        return orderProcessingTimer.record(processingLogic);
    }
}
```

Penggunaan tag memungkinkan metrik di Prometheus difilter dan diagregasi melalui kueri PromQL yang presisi.

### Anotasi @Timed dan @Counted

Untuk menghindari kode boilerplate, Micrometer menyediakan anotasi AOP yang menginstrumentasi metode secara otomatis.

```java
// PaymentService.java
// Automatic instrumentation with annotations
package com.example.monitoring.service;

import io.micrometer.core.annotation.Counted;
import io.micrometer.core.annotation.Timed;
import org.springframework.stereotype.Service;

@Service
public class PaymentService {

    // @Timed automatically creates a Timer
    // Measures each call and publishes count, sum, max
    @Timed(
        value = "payment.process.duration",
        description = "Payment processing duration",
        percentiles = {0.5, 0.95, 0.99},
        histogram = true
    )
    public PaymentResult processPayment(PaymentRequest request) {
        // Payment logic
        validatePayment(request);
        return executePayment(request);
    }

    // @Counted increments a counter on each call
    // Useful for discrete events
    @Counted(
        value = "payment.refunds.total",
        description = "Total number of refunds"
    )
    public void refundPayment(String transactionId) {
        // Refund logic
    }

    // Combining both annotations
    @Timed(value = "payment.validation.duration")
    @Counted(value = "payment.validation.total")
    private void validatePayment(PaymentRequest request) {
        // Payment validation
    }
}
```

```java
// TimedAspectConfig.java
// Required configuration to enable @Timed
package com.example.monitoring.config;

import io.micrometer.core.aop.CountedAspect;
import io.micrometer.core.aop.TimedAspect;
import io.micrometer.core.instrument.MeterRegistry;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class TimedAspectConfig {

    // Aspect required for @Timed to work
    @Bean
    TimedAspect timedAspect(MeterRegistry registry) {
        return new TimedAspect(registry);
    }

    // Aspect for @Counted
    @Bean
    CountedAspect countedAspect(MeterRegistry registry) {
        return new CountedAspect(registry);
    }
}
```

> **Batasan AOP**
>
> Anotasi @Timed dan @Counted hanya bekerja pada bean Spring dan panggilan eksternal. Panggilan internal di dalam kelas yang sama melewati proxy AOP sehingga tidak terinstrumentasi.

## Endpoint Kesehatan Kustom

### Health Indicator Bisnis

Health Indicator memverifikasi status dependensi eksternal dan komponen bisnis kritis. Spring Boot menyediakan indicator default untuk basis data, Redis, dan layanan umum lainnya.

```java
// PaymentGatewayHealthIndicator.java
// Health indicator for payment gateway
package com.example.monitoring.health;

import org.springframework.boot.actuate.health.Health;
import org.springframework.boot.actuate.health.HealthIndicator;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestClient;

import java.time.Duration;
import java.time.Instant;

@Component
public class PaymentGatewayHealthIndicator implements HealthIndicator {

    private final RestClient restClient;
    private final String gatewayHealthUrl;

    public PaymentGatewayHealthIndicator(RestClient.Builder restClientBuilder) {
        this.restClient = restClientBuilder.build();
        this.gatewayHealthUrl = "https://api.payment-gateway.com/health";
    }

    @Override
    public Health health() {
        Instant start = Instant.now();

        try {
            // Call gateway health endpoint
            var response = restClient.get()
                .uri(gatewayHealthUrl)
                .retrieve()
                .toBodilessEntity();

            Duration responseTime = Duration.between(start, Instant.now());

            if (response.getStatusCode().is2xxSuccessful()) {
                return Health.up()
                    .withDetail("responseTime", responseTime.toMillis() + "ms")
                    .withDetail("statusCode", response.getStatusCode().value())
                    .build();
            } else {
                return Health.down()
                    .withDetail("statusCode", response.getStatusCode().value())
                    .withDetail("reason", "Unexpected status code")
                    .build();
            }
        } catch (Exception e) {
            Duration responseTime = Duration.between(start, Instant.now());

            return Health.down()
                .withDetail("error", e.getClass().getSimpleName())
                .withDetail("message", e.getMessage())
                .withDetail("responseTime", responseTime.toMillis() + "ms")
                .build();
        }
    }
}
```

Indicator ini muncul otomatis di `/actuator/health` dengan nama `paymentGateway`.

### Grup Kesehatan untuk Kubernetes

Grup kesehatan memungkinkan pembuatan endpoint terpisah untuk probe liveness dan readiness pada Kubernetes.

```yaml
# application.yml
# Health groups configuration for Kubernetes
management:
  endpoint:
    health:
      group:
        # Liveness probe - is the application alive?
        liveness:
          include: livenessState
          show-details: always
        # Readiness probe - can the application receive traffic?
        readiness:
          include: readinessState,db,redis,paymentGateway
          show-details: always
        # Custom probe for critical dependencies
        critical:
          include: db,paymentGateway
          show-details: when-authorized
  health:
    # Enable Kubernetes states
    livenessstate:
      enabled: true
    readinessstate:
      enabled: true
```

```java
// KubernetesHealthConfig.java
// Programmatic health groups configuration
package com.example.monitoring.config;

import org.springframework.boot.actuate.availability.LivenessStateHealthIndicator;
import org.springframework.boot.actuate.availability.ReadinessStateHealthIndicator;
import org.springframework.boot.availability.ApplicationAvailability;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class KubernetesHealthConfig {

    @Bean
    LivenessStateHealthIndicator livenessStateHealthIndicator(
            ApplicationAvailability availability) {
        return new LivenessStateHealthIndicator(availability);
    }

    @Bean
    ReadinessStateHealthIndicator readinessStateHealthIndicator(
            ApplicationAvailability availability) {
        return new ReadinessStateHealthIndicator(availability);
    }
}
```

Probe Kubernetes kemudian diarahkan ke endpoint khusus:

```yaml
# kubernetes-deployment.yml
# Kubernetes probes configuration
spec:
  containers:
    - name: order-service
      livenessProbe:
        httpGet:
          path: /actuator/health/liveness
          port: 8080
        initialDelaySeconds: 30
        periodSeconds: 10
        failureThreshold: 3
      readinessProbe:
        httpGet:
          path: /actuator/health/readiness
          port: 8080
        initialDelaySeconds: 10
        periodSeconds: 5
        failureThreshold: 3
```

## Integrasi Prometheus dan Grafana

### Konfigurasi Scraping Prometheus

Prometheus mengumpulkan metrik dengan menanyakan endpoint `/actuator/prometheus` secara berkala. Konfigurasi menentukan target yang akan di-scrape.

```yaml
# prometheus.yml
# Prometheus configuration for Spring Boot
global:
  scrape_interval: 15s
  evaluation_interval: 15s

scrape_configs:
  - job_name: 'spring-boot-apps'
    metrics_path: '/actuator/prometheus'
    scrape_interval: 10s
    static_configs:
      - targets:
          - 'order-service:8080'
          - 'payment-service:8080'
          - 'inventory-service:8080'
    # Relabeling to add metadata
    relabel_configs:
      - source_labels: [__address__]
        target_label: instance
        regex: '([^:]+):\d+'
        replacement: '${1}'

  # Kubernetes service discovery
  - job_name: 'kubernetes-pods'
    kubernetes_sd_configs:
      - role: pod
    relabel_configs:
      # Only scrape pods with annotation
      - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_scrape]
        action: keep
        regex: true
      - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_path]
        action: replace
        target_label: __metrics_path__
        regex: (.+)
```

### Metrik JVM Default

Actuator yang dilengkapi Micrometer secara otomatis menyajikan metrik JVM yang detail. Metrik penting untuk monitoring tercantum berikut.

```promql
# PromQL queries for JVM monitoring

# Heap memory usage
jvm_memory_used_bytes{area="heap"}

# Memory usage percentage
jvm_memory_used_bytes{area="heap"} / jvm_memory_max_bytes{area="heap"} * 100

# Active threads
jvm_threads_live_threads

# Garbage collection - time spent
rate(jvm_gc_pause_seconds_sum[5m])

# GC count per minute
rate(jvm_gc_pause_seconds_count[1m]) * 60

# CPU used by JVM
process_cpu_usage

# Active database connections
hikaricp_connections_active

# Connection pool utilization
hikaricp_connections_active / hikaricp_connections_max * 100
```

```java
// CustomJvmMetrics.java
// Additional JVM metrics
package com.example.monitoring.metrics;

import io.micrometer.core.instrument.Gauge;
import io.micrometer.core.instrument.MeterRegistry;
import io.micrometer.core.instrument.binder.MeterBinder;
import org.springframework.stereotype.Component;

import java.lang.management.ManagementFactory;
import java.lang.management.OperatingSystemMXBean;

@Component
public class CustomJvmMetrics implements MeterBinder {

    @Override
    public void bindTo(MeterRegistry registry) {
        OperatingSystemMXBean osBean = ManagementFactory.getOperatingSystemMXBean();

        // System load average
        Gauge.builder("system.load.average", osBean, OperatingSystemMXBean::getSystemLoadAverage)
            .description("System load average over 1 minute")
            .register(registry);

        // Available processors count
        Gauge.builder("system.cpu.count", osBean, OperatingSystemMXBean::getAvailableProcessors)
            .description("Number of available processors")
            .register(registry);

        // Application uptime
        Gauge.builder("application.uptime.seconds",
                ManagementFactory.getRuntimeMXBean(),
                bean -> bean.getUptime() / 1000.0)
            .description("Application uptime in seconds")
            .register(registry);
    }
}
```

### Dashboard Grafana Siap Pakai

Grafana menyediakan dashboard yang sudah dikonfigurasi untuk Spring Boot. Dashboard dengan ID 12900 memberikan tinjauan menyeluruh atas metrik Actuator.

```json
{
  "annotations": {
    "list": []
  },
  "panels": [
    {
      "title": "Request Rate",
      "type": "graph",
      "targets": [
        {
          "expr": "rate(http_server_requests_seconds_count{application=\"$application\"}[5m])",
          "legendFormat": "{{method}} {{uri}} - {{status}}"
        }
      ]
    },
    {
      "title": "Response Time P99",
      "type": "graph",
      "targets": [
        {
          "expr": "histogram_quantile(0.99, rate(http_server_requests_seconds_bucket{application=\"$application\"}[5m]))",
          "legendFormat": "{{method}} {{uri}}"
        }
      ]
    },
    {
      "title": "Error Rate",
      "type": "singlestat",
      "targets": [
        {
          "expr": "sum(rate(http_server_requests_seconds_count{application=\"$application\",status=~\"5..\"}[5m])) / sum(rate(http_server_requests_seconds_count{application=\"$application\"}[5m])) * 100"
        }
      ]
    }
  ]
}
```

> **Impor di Grafana**
>
> Untuk mengimpor dashboard: Grafana → Dashboards → Import → ID 12900 (Spring Boot Statistics) atau 4701 (JVM Micrometer). Dashboard ini dapat langsung dipakai bersama metrik Actuator standar.

## Alerting dengan Prometheus

### Aturan Alert Penting

Aturan alert Prometheus memicu notifikasi ketika metrik melewati ambang batas kritis.

```yaml
# alerting-rules.yml
# Alert rules for Spring Boot applications
groups:
  - name: spring-boot-alerts
    rules:
      # Alert if application is down
      - alert: ApplicationDown
        expr: up{job="spring-boot-apps"} == 0
        for: 1m
        labels:
          severity: critical
        annotations:
          summary: "Application {{ $labels.instance }} is down"
          description: "{{ $labels.instance }} has been down for more than 1 minute"

      # Alert on HTTP error rate
      - alert: HighErrorRate
        expr: |
          sum(rate(http_server_requests_seconds_count{status=~"5.."}[5m])) by (application)
          /
          sum(rate(http_server_requests_seconds_count[5m])) by (application)
          > 0.05
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "High error rate on {{ $labels.application }}"
          description: "Error rate is {{ $value | humanizePercentage }}"

      # Alert on P99 latency
      - alert: HighLatency
        expr: |
          histogram_quantile(0.99,
            rate(http_server_requests_seconds_bucket[5m])
          ) > 2
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "High latency detected"
          description: "P99 latency is {{ $value | humanizeDuration }}"

      # Heap memory alert
      - alert: HighHeapUsage
        expr: |
          jvm_memory_used_bytes{area="heap"}
          / jvm_memory_max_bytes{area="heap"}
          > 0.85
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "High heap memory usage on {{ $labels.instance }}"
          description: "Heap usage is at {{ $value | humanizePercentage }}"

      # Database connection pool exhausted alert
      - alert: DatabaseConnectionPoolExhausted
        expr: |
          hikaricp_connections_active
          / hikaricp_connections_max
          > 0.9
        for: 2m
        labels:
          severity: critical
        annotations:
          summary: "Database connection pool nearly exhausted"
          description: "{{ $value | humanizePercentage }} of connections in use"

      # Excessive GC alert
      - alert: HighGCPause
        expr: |
          rate(jvm_gc_pause_seconds_sum[5m])
          / rate(jvm_gc_pause_seconds_count[5m])
          > 0.5
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "High GC pause time"
          description: "Average GC pause is {{ $value | humanizeDuration }}"
```

Alert tersebut mencakup masalah produksi yang paling umum: ketersediaan, performa, dan sumber daya.

## Metrik HTTP dan Basis Data

### Instrumentasi Otomatis Permintaan HTTP

Spring Boot 3 menginstrumentasi seluruh permintaan HTTP masuk secara otomatis dengan metrik yang detail.

```yaml
# application.yml
# HTTP metrics configuration
management:
  metrics:
    distribution:
      # Enable histograms for percentiles
      percentiles-histogram:
        http.server.requests: true
      percentiles:
        http.server.requests: 0.5, 0.75, 0.95, 0.99
      # Define SLA buckets
      slo:
        http.server.requests: 100ms, 500ms, 1s, 2s
    tags:
      # Global tags added to all metrics
      application: ${spring.application.name}
      environment: ${spring.profiles.active:default}
```

```java
// WebMvcMetricsConfig.java
// HTTP tags customization
package com.example.monitoring.config;

import io.micrometer.core.instrument.Tag;
import org.springframework.boot.actuate.metrics.web.servlet.WebMvcTagsContributor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.HandlerMapping;

import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.util.Collections;

@Configuration
public class WebMvcMetricsConfig {

    @Bean
    WebMvcTagsContributor customTagsContributor() {
        return (request, response, handler, exception) -> {
            // Add custom tags to HTTP metrics
            String userId = request.getHeader("X-User-Id");
            String tenantId = request.getHeader("X-Tenant-Id");

            return java.util.List.of(
                Tag.of("user.type", userId != null ? "authenticated" : "anonymous"),
                Tag.of("tenant", tenantId != null ? tenantId : "default")
            );
        };
    }
}
```

### Metrik HikariCP dan Kueri SQL

Metrik connection pool HikariCP disajikan secara otomatis. Untuk kueri SQL, konfigurasi tambahan mengaktifkan tracing durasinya.

```yaml
# application.yml
# HikariCP configuration with metrics
spring:
  datasource:
    hikari:
      pool-name: OrderServicePool
      maximum-pool-size: 20
      minimum-idle: 5
      connection-timeout: 30000
      idle-timeout: 600000
      max-lifetime: 1800000
      # Enable detailed metrics
      register-mbeans: true
```

```java
// DataSourceMetricsConfig.java
// Additional metrics for SQL queries
package com.example.monitoring.config;

import io.micrometer.core.instrument.MeterRegistry;
import net.ttddyy.dsproxy.listener.logging.SLF4JLogLevel;
import net.ttddyy.dsproxy.support.ProxyDataSourceBuilder;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;

@Configuration
public class DataSourceMetricsConfig {

    @Bean
    @Primary
    DataSource metricsDataSource(
            DataSourceProperties properties,
            MeterRegistry registry) {

        // Original DataSource
        DataSource originalDataSource = properties
            .initializeDataSourceBuilder()
            .build();

        // Proxy with metrics
        return ProxyDataSourceBuilder.create(originalDataSource)
            .name("order-service-db")
            .listener(new MicrometerQueryMetricsListener(registry))
            .logQueryBySlf4j(SLF4JLogLevel.DEBUG)
            .build();
    }
}
```

```java
// MicrometerQueryMetricsListener.java
// Listener for SQL query metrics
package com.example.monitoring.metrics;

import io.micrometer.core.instrument.MeterRegistry;
import io.micrometer.core.instrument.Timer;
import net.ttddyy.dsproxy.ExecutionInfo;
import net.ttddyy.dsproxy.QueryInfo;
import net.ttddyy.dsproxy.listener.QueryExecutionListener;

import java.util.List;
import java.util.concurrent.TimeUnit;

public class MicrometerQueryMetricsListener implements QueryExecutionListener {

    private final Timer queryTimer;

    public MicrometerQueryMetricsListener(MeterRegistry registry) {
        this.queryTimer = Timer.builder("sql.query.duration")
            .description("SQL query execution duration")
            .publishPercentiles(0.5, 0.95, 0.99)
            .register(registry);
    }

    @Override
    public void beforeQuery(ExecutionInfo execInfo, List<QueryInfo> queryInfoList) {
        // Before execution
    }

    @Override
    public void afterQuery(ExecutionInfo execInfo, List<QueryInfo> queryInfoList) {
        // Record duration for each query
        long elapsedTime = execInfo.getElapsedTime();
        queryTimer.record(elapsedTime, TimeUnit.MILLISECONDS);
    }
}
```

## Praktik Terbaik untuk Produksi

### Kardinalitas Metrik

Kardinalitas yang berlebihan menurunkan performa Prometheus. Setiap kombinasi tag yang unik menciptakan deret waktu tersendiri.

```java
// AntiPatternHighCardinality.java
// ❌ AVOID - Explosive cardinality
package com.example.monitoring.antipattern;

@Service
public class AntiPatternHighCardinality {

    private final MeterRegistry registry;

    // ❌ BAD: userId creates one series per user
    public void trackUserAction(String userId, String action) {
        Counter.builder("user.actions")
            .tag("userId", userId)  // Millions of possible values!
            .tag("action", action)
            .register(registry)
            .increment();
    }
}
```

```java
// GoodPracticeCardinality.java
// ✅ Controlled cardinality
package com.example.monitoring.bestpractice;

@Service
public class GoodPracticeCardinality {

    private final MeterRegistry registry;

    // ✅ GOOD: User category instead of ID
    public void trackUserAction(User user, String action) {
        Counter.builder("user.actions")
            .tag("userType", user.getSubscriptionType())  // FREE, PREMIUM, ENTERPRISE
            .tag("action", action)
            .register(registry)
            .increment();
    }

    // ✅ GOOD: Grouping by range
    public void trackResponseTime(long responseTimeMs) {
        String bucket = categorizeResponseTime(responseTimeMs);
        Counter.builder("response.time.bucket")
            .tag("bucket", bucket)  // fast, normal, slow, very_slow
            .register(registry)
            .increment();
    }

    private String categorizeResponseTime(long ms) {
        if (ms < 100) return "fast";
        if (ms < 500) return "normal";
        if (ms < 2000) return "slow";
        return "very_slow";
    }
}
```

### Konfigurasi Siap Produksi

```yaml
# application-production.yml
# Optimized configuration for production
management:
  endpoints:
    web:
      exposure:
        include: health,info,prometheus
  endpoint:
    health:
      show-details: when-authorized
      probes:
        enabled: true
  metrics:
    export:
      prometheus:
        enabled: true
        step: 30s
    distribution:
      percentiles-histogram:
        http.server.requests: true
      minimum-expected-value:
        http.server.requests: 1ms
      maximum-expected-value:
        http.server.requests: 30s
    tags:
      application: ${spring.application.name}
      environment: production
      version: ${app.version:unknown}
  server:
    # Separate port for management endpoints
    port: 9090

# Disable non-essential endpoints in production
  endpoint:
    env:
      enabled: false
    beans:
      enabled: false
    configprops:
      enabled: false
    mappings:
      enabled: false
```

## Kesimpulan

Spring Boot Actuator yang dipadukan dengan Micrometer dan Prometheus menghadirkan solusi monitoring yang lengkap:

✅ **Konfigurasi minimal** — endpoint siap produksi dengan Spring Boot Starter

✅ **Metrik JVM otomatis** — memori, thread, GC, CPU tanpa kode tambahan

✅ **Metrik kustom** — Counter, Gauge, Timer dengan anotasi @Timed/@Counted

✅ **Health Indicator** — pemeriksaan dependensi eksternal dan status Kubernetes

✅ **Integrasi Prometheus** — format standar untuk scraping dan alerting

✅ **Keamanan bawaan** — kontrol akses pada endpoint sensitif

✅ **Dashboard Grafana** — visualisasi instan dengan dashboard yang sudah dikonfigurasi

✅ **Alerting** — aturan PromQL untuk mendeteksi anomali produksi

Stack observability ini menjadi fondasi yang esensial untuk menjalankan aplikasi Spring Boot di produksi dengan percaya diri.

---

Source: SharpSkill (https://sharpskill.dev), tech interview preparation for your real stack.
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