Metrics Monitoring System - Architecture

High-Level Architecture

┌─────────────────────────────────────────────────────────────┐
│                    Monitored Services                        │
├─────────────────────────────────────────────────────────────┤
│  Applications  │  Databases  │  Servers  │  Containers      │
│  (Metrics      │  (Metrics   │  (Node    │  (cAdvisor)     │
│   Endpoint)    │   Exporter) │  Exporter)│                  │
└────────┬────────────┬─────────────┬────────────┬────────────┘
         │            │             │            │
         │ Pull       │ Pull        │ Pull       │ Push
         │            │             │            │
    ┌────▼────────────▼─────────────▼────────────▼────┐
    │           Service Discovery                      │
    │  (Consul, K8s API, DNS, Static Config)          │
    └────────────────────┬────────────────────────────┘
                         │
         ┌───────────────┴───────────────┐
         │                               │
    ┌────▼────┐                    ┌─────▼─────┐
    │ Scraper │                    │   Push    │
    │  Pool   │                    │  Gateway  │
    └────┬────┘                    └─────┬─────┘
         │                               │
         └───────────────┬───────────────┘
                         │
                    ┌────▼────┐
                    │  Kafka  │ (Metric Stream)
                    └────┬────┘
                         │
         ┌───────────────┼───────────────┐
         │               │               │
    ┌────▼────┐    ┌─────▼─────┐   ┌───▼────┐
    │  Write  │    │   Alert   │   │  Rule  │
    │  Path   │    │ Evaluator │   │ Manager│
    └────┬────┘    └─────┬─────┘   └────────┘
         │               │
         │               ▼
         │         ┌──────────┐
         │         │  Alert   │
         │         │ Manager  │
         │         └─────┬────┘
         │               │
         │               ▼
         │         ┌──────────┐
         │         │Notification│
         │         │  Service │
         │         └──────────┘
         │
    ┌────▼────────────────────────────┐
    │    Time-Series Database         │
    │  (Prometheus / VictoriaMetrics) │
    └────┬────────────────────────────┘
         │
    ┌────▼────────────────────────────┐
    │         Query Layer              │
    ├──────────────────────────────────┤
    │  Query Engine  │  Cache  │  API  │
    └────┬─────────────────────────────┘
         │
    ┌────▼────────────────────────────┐
    │      Application Layer           │
    ├──────────────────────────────────┤
    │  Dashboard  │  API  │  Grafana  │
    └──────────────────────────────────┘

Component Details

1. Service Discovery

Automatically discovers monitoring targets
Supports Kubernetes, Consul, DNS, static configs
Updates target list dynamically
Health checking of targets

2. Metric Collection

Scraper Pool: Pull metrics from HTTP endpoints
Push Gateway: Accept pushed metrics
Batching: Collect metrics in batches
Compression: Compress metric data

3. Write Path

Kafka for buffering and reliability
Write to time-series database
Replication across nodes
Compression and encoding

4. Time-Series Database

Stores metric data efficiently
Columnar storage format
Automatic downsampling
Retention policies

5. Alert System

Evaluates alert rules periodically
Manages alert state (pending, firing, resolved)
Routes alerts to notification channels
Deduplication and grouping

6. Query Layer

PromQL-compatible query language
Query optimization and caching
Aggregation and downsampling
Federation support

7. Visualization

Dashboard builder
Real-time metric graphs
Alert visualization
Custom panels

Data Flow

Metric Ingestion Flow

1. Service Discovery finds targets
2. Scraper pulls metrics every 15s
3. Metrics sent to Kafka
4. Write path consumes from Kafka
5. Data written to time-series DB
6. Indexes updated

Query Flow

1. User requests dashboard
2. Query service checks cache
3. If miss, query time-series DB
4. Apply aggregations
5. Cache result
6. Return to user

Alert Flow

1. Alert evaluator runs rules every 30s
2. Query time-series DB for metrics
3. Evaluate conditions
4. Update alert state
5. If firing, send to notification service
6. Deliver via configured channels

This architecture provides a scalable, reliable foundation for comprehensive monitoring at massive scale.