Monitoring & Observability

Overview

SGIVU implements comprehensive observability across all services using Spring Boot Actuator, Micrometer Tracing, and Zipkin for distributed tracing. This enables real-time health monitoring, performance analysis, and distributed request correlation.

Health Checks

Actuator Endpoints

All Spring Boot services expose health check endpoints via Spring Boot Actuator:

Service	Endpoint	Port
sgivu-auth	`/actuator/health`	9000
sgivu-gateway	`/actuator/health`	8080
sgivu-config	`/actuator/health`	8888
sgivu-discovery	`/actuator/health`	8761
sgivu-user	`/actuator/health`	8081
sgivu-client	`/actuator/health`	8082
sgivu-vehicle	`/actuator/health`	8083
sgivu-purchase-sale	`/actuator/health`	8084
sgivu-ml (FastAPI)	`/health` or `/actuator/health`	8000

Health Check Examples

Spring Boot Services

# Gateway health
curl http://localhost:8080/actuator/health

# Response
{
  "status": "UP",
  "components": {
    "diskSpace": {
      "status": "UP",
      "details": {
        "total": 250790436864,
        "free": 100000000000,
        "threshold": 10485760
      }
    },
    "ping": {
      "status": "UP"
    },
    "redis": {
      "status": "UP",
      "details": {
        "version": "7.0.0"
      }
    }
  }
}

ML Service (FastAPI)

curl http://localhost:8000/health

# Response
{
  "status": "healthy",
  "service": "sgivu-ml",
  "version": "0.1.0"
}

Environment-Specific Exposure

Actuator endpoint exposure varies by profile: Development (application-dev.yml):

management:
  endpoints:
    web:
      exposure:
        include: health,info,metrics,prometheus,env,configprops

Production (application-prod.yml):

management:
  endpoints:
    web:
      exposure:
        include: health,info

In production, restrict actuator endpoints to internal networks or require authentication. Exposing metrics and environment details publicly is a security risk.

Liveness and Readiness Probes

For Kubernetes deployments:

management:
  endpoint:
    health:
      probes:
        enabled: true
  health:
    livenessState:
      enabled: true
    readinessState:
      enabled: true

Endpoints:

GET /actuator/health/liveness: Liveness probe (should restart if DOWN)
GET /actuator/health/readiness: Readiness probe (should not receive traffic if DOWN)

Distributed Tracing

Zipkin Integration

SGIVU uses Zipkin for distributed tracing with MySQL storage for persistence.

Architecture

┌──────────────┐
│   Client     │
└──────┬───────┘
       │ Request (trace-id generated)
       ▼
┌──────────────┐  span  ┌───────────┐
│   Gateway    ├────────►│  Zipkin   │
└──────┬───────┘         │   :9411   │
       │                 └─────┬─────┘
       │ (trace-id relay)      │
       ▼                       │ Store
┌──────────────┐  span         ▼
│     User     ├────────► ┌──────────┐
│   Service    │          │  MySQL   │
└──────┬───────┘          │  Zipkin  │
       │                  │    DB    │
       │ (trace-id relay) └──────────┘
       ▼
┌──────────────┐  span
│     Auth     ├────────► Zipkin
│   Service    │
└──────────────┘

Zipkin Configuration

Docker Compose (docker-compose.yml):

sgivu-zipkin:
  container_name: sgivu-zipkin
  image: openzipkin/zipkin
  ports:
    - "9411:9411"
  restart: always
  networks:
    - sgivu-network
  env_file: .env
  depends_on:
    - sgivu-mysql

Environment Variables:

STORAGE_TYPE=mysql
MYSQL_HOST=sgivu-mysql
MYSQL_DB=sgivu_zipkin_db
MYSQL_USER=zipkin
MYSQL_PASS=your-mysql-password

Service Configuration

Each Spring Boot service configures tracing:

management:
  tracing:
    sampling:
      probability: 1.0  # 100% sampling in dev, reduce in prod (e.g., 0.1)
  zipkin:
    tracing:
      endpoint: http://sgivu-zipkin:9411/api/v2/spans

Production Sampling:

management:
  tracing:
    sampling:
      probability: 0.1  # Sample 10% of requests

Lower sampling rates reduce overhead in high-traffic production environments while maintaining observability for debugging.

Trace ID Propagation

SGIVU uses custom filters to ensure trace ID propagation:

Gateway: ZipkinTracingGlobalFilter

File: apps/backend/sgivu-gateway/.../ZipkinTracingGlobalFilter.java Actions:

Creates spans for each request
Adds X-Trace-Id header to requests and responses
Tags spans with status code and duration

Example Response Headers:

X-Trace-Id: 5f3e8c9a2b1d4e6f
X-Application-Context: sgivu-gateway:prod:8080

Trace Context

Logged Attributes:

trace-id: Unique identifier for the entire request flow
span-id: Unique identifier for each service call
parent-span-id: Parent span (for nested calls)
service.name: Service name (e.g., sgivu-gateway)
http.method: Request method (GET, POST, etc.)
http.url: Request URL
http.status_code: Response status

Zipkin UI

Access: http://localhost:9411 (development) or http://your-ec2-hostname/zipkin/ (production)

Features

1. Trace Search

Search by service name
Search by span name
Search by tag (e.g., http.status_code=500)
Time range filtering

2. Trace Details

Complete request timeline
Service dependencies
Span duration breakdown
Tags and annotations

3. Service Dependencies

Visualize service call graph
Identify bottlenecks
Detect circular dependencies

Example Trace:

Gateway (200ms)
├─ User Service (50ms)
│  └─ Auth Service (20ms)  ← Credential validation
├─ Client Service (30ms)
└─ Vehicle Service (80ms)
   └─ S3 Upload (60ms)      ← Image upload

Custom Spans

Services create custom spans for specific operations: Auth Service (sgivu-auth):

CredentialsValidationService.validateCredentials(): Span for credential validation
JpaUserDetailsService.loadUserByUsername(): Span for user loading

Example Code:

@Observed(name = "credentials.validation",
          contextualName = "validate-user-credentials")
public boolean validateCredentials(String username, String password) {
    // Validation logic
}

Service Discovery Monitoring

Eureka Dashboard

Access: http://localhost:8761 (development) or http://your-ec2-hostname/eureka/ (production)

Dashboard Features

1. Instance Status

Service name
Instance count
Instance IDs
Status (UP, DOWN, OUT_OF_SERVICE)

2. System Information

Environment
Data center
Uptime

3. Registered Applications

Application         | AMIs        | Availability Zones | Status
--------------------|-------------|--------------------|---------
SGIVU-AUTH          | n/a (1)     | (1)               | UP (1)
SGIVU-GATEWAY       | n/a (1)     | (1)               | UP (1)
SGIVU-USER          | n/a (1)     | (1)               | UP (1)
SGIVU-CLIENT        | n/a (1)     | (1)               | UP (1)
SGIVU-VEHICLE       | n/a (1)     | (1)               | UP (1)
SGIVU-PURCHASE-SALE | n/a (1)     | (1)               | UP (1)

REST API

Get All Applications:

curl http://localhost:8761/eureka/apps

Get Specific Application:

curl http://localhost:8761/eureka/apps/SGIVU-GATEWAY

Response (XML):

<application>
  <name>SGIVU-GATEWAY</name>
  <instance>
    <instanceId>sgivu-gateway:8080</instanceId>
    <hostName>sgivu-gateway</hostName>
    <app>SGIVU-GATEWAY</app>
    <ipAddr>172.18.0.10</ipAddr>
    <status>UP</status>
    <port enabled="true">8080</port>
    <healthCheckUrl>http://sgivu-gateway:8080/actuator/health</healthCheckUrl>
  </instance>
</application>

Eureka dashboard is exposed without authentication. In production, use IP whitelisting or VPN access.

Logging

Log Levels

Development:

logging:
  level:
    root: INFO
    com.sgivu: DEBUG
    org.springframework.security: DEBUG
    org.springframework.cloud.gateway: DEBUG

Production:

logging:
  level:
    root: INFO
    com.sgivu: INFO
    org.springframework.security: WARN

Structured Logging

Services use SLF4J with Logback for structured logging: Log Format:

%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] %-5level [%X{trace-id},%X{span-id}] %logger{36} - %msg%n

Example Log:

2026-03-06 10:15:23.456 [http-nio-8080-exec-1] INFO  [5f3e8c9a2b1d4e6f,a1b2c3d4e5f6] c.s.g.filter.ZipkinTracingGlobalFilter - Request: GET /v1/users
2026-03-06 10:15:23.512 [http-nio-8080-exec-1] INFO  [5f3e8c9a2b1d4e6f,a1b2c3d4e5f6] c.s.g.filter.ZipkinTracingGlobalFilter - Response: 200 (56ms)

Viewing Logs

Docker Compose:

# All services
docker compose logs -f

# Specific service
docker compose logs -f sgivu-gateway

# Last 100 lines
docker compose logs --tail=100 sgivu-gateway

# Since timestamp
docker compose logs --since 2026-03-06T10:00:00 sgivu-gateway

Filter by Trace ID:

docker compose logs sgivu-gateway | grep "5f3e8c9a2b1d4e6f"

Metrics

Micrometer Metrics

Spring Boot services expose Prometheus-compatible metrics:

curl http://localhost:8080/actuator/metrics

# Response
{
  "names": [
    "jvm.memory.used",
    "jvm.memory.max",
    "http.server.requests",
    "spring.cloud.gateway.requests",
    "resilience4j.circuitbreaker.state",
    "system.cpu.usage"
  ]
}

Key Metrics

JVM Metrics

jvm.memory.used: Memory usage by heap/non-heap
jvm.threads.live: Active thread count
jvm.gc.pause: Garbage collection pause times

HTTP Metrics

http.server.requests: Request count, duration, status
http.client.requests: Outbound request metrics

Gateway Metrics

spring.cloud.gateway.requests: Gateway request count by route
gateway.requests.duration: Request duration histogram

Circuit Breaker Metrics

resilience4j.circuitbreaker.state: Circuit breaker state (closed, open, half-open)
resilience4j.circuitbreaker.calls: Call results (success, failure)
resilience4j.circuitbreaker.buffered.calls: Buffered calls in sliding window

Redis Metrics (Gateway)

spring.data.redis.connections.active: Active Redis connections
spring.session.redis.operations: Session operations (save, load, delete)

Prometheus Integration

Enable Prometheus Endpoint:

management:
  endpoints:
    web:
      exposure:
        include: health,info,prometheus
  metrics:
    export:
      prometheus:
        enabled: true

Scrape Configuration (prometheus.yml):

scrape_configs:
  - job_name: 'sgivu-gateway'
    metrics_path: '/actuator/prometheus'
    static_configs:
      - targets: ['sgivu-gateway:8080']
  
  - job_name: 'sgivu-auth'
    metrics_path: '/actuator/prometheus'
    static_configs:
      - targets: ['sgivu-auth:9000']
  
  - job_name: 'sgivu-user'
    metrics_path: '/actuator/prometheus'
    static_configs:
      - targets: ['sgivu-user:8081']

Alerting

Health Check Monitoring

Simple Script (monitor-health.sh):

#!/bin/bash

SERVICES=(
  "http://localhost:8080/actuator/health"  # Gateway
  "http://localhost:9000/actuator/health"  # Auth
  "http://localhost:8081/actuator/health"  # User
  "http://localhost:8082/actuator/health"  # Client
  "http://localhost:8083/actuator/health"  # Vehicle
  "http://localhost:8084/actuator/health"  # Purchase-sale
  "http://localhost:8000/health"           # ML
)

for SERVICE in "${SERVICES[@]}"; do
  STATUS=$(curl -s -o /dev/null -w "%{http_code}" "$SERVICE")
  if [ "$STATUS" -ne 200 ]; then
    echo "ALERT: $SERVICE is DOWN (HTTP $STATUS)"
    # Send alert (email, Slack, PagerDuty, etc.)
  fi
done

Prometheus Alertmanager

Alert Rules (alerts.yml):

groups:
  - name: sgivu_alerts
    interval: 30s
    rules:
      - alert: ServiceDown
        expr: up{job=~"sgivu-.*"} == 0
        for: 1m
        labels:
          severity: critical
        annotations:
          summary: "SGIVU service {{ $labels.job }} is down"
          description: "{{ $labels.instance }} has been down for more than 1 minute"
      
      - alert: HighErrorRate
        expr: rate(http_server_requests_seconds_count{status=~"5.."}[5m]) > 0.1
        for: 5m
        labels:
          severity: warning
        annotations:
          summary: "High error rate on {{ $labels.job }}"
          description: "Error rate is {{ $value }} req/s"
      
      - alert: CircuitBreakerOpen
        expr: resilience4j_circuitbreaker_state{state="open"} == 1
        for: 2m
        labels:
          severity: warning
        annotations:
          summary: "Circuit breaker {{ $labels.name }} is OPEN"
          description: "Circuit breaker has been open for more than 2 minutes"

Performance Monitoring

Request Duration Analysis

Zipkin: Analyze slow requests

Navigate to Zipkin UI
Set duration filter (e.g., >1000ms)
Identify bottleneck services
Drill down into span details

Circuit Breaker Monitoring

Gateway uses Resilience4j circuit breakers for resilience: Configuration:

resilience4j:
  circuitbreaker:
    configs:
      default:
        slidingWindowSize: 10
        minimumNumberOfCalls: 5
        failureRateThreshold: 50
        waitDurationInOpenState: 10000
        permittedNumberOfCallsInHalfOpenState: 3

States:

CLOSED: Normal operation
OPEN: Failures exceeded threshold, requests fail fast
HALF_OPEN: Testing if service recovered

Metrics:

curl http://localhost:8080/actuator/metrics/resilience4j.circuitbreaker.state

Database Connection Pool

Monitor HikariCP connection pool:

curl http://localhost:8081/actuator/metrics/hikaricp.connections.active
curl http://localhost:8081/actuator/metrics/hikaricp.connections.idle

Troubleshooting

No Traces in Zipkin

Problem: Services are running but no traces appear in Zipkin Solutions:

Verify Zipkin URL:

management:
  zipkin:
    tracing:
      endpoint: http://sgivu-zipkin:9411/api/v2/spans

Check sampling probability:

management:
  tracing:
    sampling:
      probability: 1.0  # 100% sampling

Test Zipkin connectivity:

docker compose exec sgivu-gateway curl -X POST http://sgivu-zipkin:9411/api/v2/spans

Check Zipkin logs:
```
docker compose logs sgivu-zipkin
```

Service Not Appearing in Eureka

Problem: Service is running but not registered Solutions:

Verify Eureka configuration:

eureka:
  client:
    service-url:
      defaultZone: http://sgivu-discovery:8761/eureka
    register-with-eureka: true
    fetch-registry: true

Check network connectivity:

docker compose exec sgivu-user curl http://sgivu-discovery:8761

Review service logs for registration errors:

docker compose logs sgivu-user | grep -i eureka

High Trace Volume

Problem: Zipkin database growing rapidly Solutions:

Reduce sampling rate:

management:
  tracing:
    sampling:
      probability: 0.1  # 10% sampling

Configure Zipkin retention:

ZIPKIN_STORAGE_MYSQL_MAX_TRACE_AGE=86400000  # 1 day in milliseconds

Implement trace cleanup:

DELETE FROM zipkin_spans WHERE start_ts < UNIX_TIMESTAMP(NOW() - INTERVAL 7 DAY) * 1000000;

Next Steps

Deployment Architecture: Infrastructure overview
Docker Compose: Service orchestration
Nginx Configuration: Reverse proxy setup

Overview

Getting Started

Core Features

Infrastructure

Security

​Overview

​Health Checks

​Actuator Endpoints

​Health Check Examples

​Spring Boot Services

​ML Service (FastAPI)

​Environment-Specific Exposure

​Liveness and Readiness Probes

​Distributed Tracing

​Zipkin Integration

​Architecture

​Zipkin Configuration

​Service Configuration

​Trace ID Propagation

​Gateway: ZipkinTracingGlobalFilter

​Trace Context

​Zipkin UI

​Features

​Custom Spans

​Service Discovery Monitoring

​Eureka Dashboard

​Dashboard Features

​REST API

​Logging

​Log Levels

​Structured Logging

​Viewing Logs

​Metrics

​Micrometer Metrics

​Key Metrics

​JVM Metrics

​HTTP Metrics

​Gateway Metrics

​Circuit Breaker Metrics

​Redis Metrics (Gateway)

​Prometheus Integration

​Alerting

​Health Check Monitoring

​Prometheus Alertmanager

​Performance Monitoring

​Request Duration Analysis

​Circuit Breaker Monitoring

​Database Connection Pool

​Troubleshooting

​No Traces in Zipkin

​Service Not Appearing in Eureka

​High Trace Volume

​Next Steps

Build docs developers (and LLMs) love

Overview

Health Checks

Actuator Endpoints

Health Check Examples

Spring Boot Services

ML Service (FastAPI)

Environment-Specific Exposure

Liveness and Readiness Probes

Distributed Tracing

Zipkin Integration

Architecture

Zipkin Configuration

Service Configuration

Trace ID Propagation

Gateway: ZipkinTracingGlobalFilter

Trace Context

Zipkin UI

Features

Custom Spans

Service Discovery Monitoring

Eureka Dashboard

Dashboard Features

REST API

Logging

Log Levels

Structured Logging

Viewing Logs

Metrics

Micrometer Metrics

Key Metrics

JVM Metrics

HTTP Metrics

Gateway Metrics

Circuit Breaker Metrics

Redis Metrics (Gateway)

Prometheus Integration

Alerting

Health Check Monitoring

Prometheus Alertmanager

Performance Monitoring

Request Duration Analysis

Circuit Breaker Monitoring

Database Connection Pool

Troubleshooting

No Traces in Zipkin

Service Not Appearing in Eureka

High Trace Volume

Next Steps