Spring Boot Actuator, Prometheus, and Grafana

 Spring Boot Actuator, Prometheus, and Grafana usually work together as a monitoring stack::

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🔹 1. Spring Boot Actuator

Purpose: Adds production-ready features to a Spring Boot app.
Uses:

• Exposes health checks (e.g., /actuator/health) → check if the app is alive.

• Provides metrics endpoints (e.g., /actuator/metrics) → JVM memory, CPU, HTTP request counts, datasource stats, etc.

• Allows application monitoring & management → shutdown, environment info, logging levels (if enabled).

• Acts as the data source for Prometheus when you add the micrometer-registry-prometheus dependency (exposes /actuator/prometheus).

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🔹 2. Prometheus

Purpose: A time-series database & monitoring system.
Uses:

• Scrapes metrics from targets (like /actuator/prometheus from your Spring Boot app).

• Stores metrics as time series data.

• Supports PromQL (Prometheus Query Language) to query and aggregate data.

• Provides alerting (integrates with Alertmanager to send alerts via email, Slack, etc.).

• Efficient for real-time monitoring of microservices, infrastructure, and applications.

Example: Prometheus pulls http_server_requests_seconds_count from Actuator and stores it with timestamps → lets you know how many requests hit your app.

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🔹 3. Grafana

Purpose: A visualization and analytics tool.
Uses:

• Connects to Prometheus (or other data sources) and builds dashboards.

• Lets you plot charts, graphs, heatmaps for metrics.

• Helps in root-cause analysis by correlating metrics (e.g., “CPU high → request latency increases”).

• Can set up alerts with custom thresholds and send notifications (email, Teams, Slack, etc.).

• Used to present monitoring data in a clear, user-friendly way for devs, ops, and managers.

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🔗 How They Work Together

1. Spring Boot Actuator → exposes metrics in a format Prometheus can read.

2. Prometheus → scrapes those metrics at intervals (e.g., every 15s), stores them, and lets you query them.

3. Grafana → queries Prometheus and builds interactive dashboards to visualize application health & performance.

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✅ In short:

• Actuator = generates app metrics.

• Prometheus = collects, stores, and queries metrics.

• Grafana = visualizes and alerts on metrics.