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1️⃣ What is Prometheus?

Prometheus is an open-source monitoring and alerting system designed primarily for cloud-native and Kubernetes environments, but it works equally well with VMs, bare-metal servers, and applications.

Key Characteristics

• ✅ Monitoring Tool
• ✅ Database
• ✅ Time-Series Database (TSDB)
• ✅ Cloud-native & Kubernetes core component
• ✅ Written in Go
• ✅ Runs on any OS
• ✅ Pull-based architecture
• ✅ Highly scalable & reliable

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2️⃣ Prometheus as a Time-Series Database

Prometheus stores data as time-series, meaning every data point is associated with a timestamp.

Time-Series Format

(timestamp, metric_name, value, labels)

Example

Timestamp (epoch)	Metric	Value	Labels
1700000000	cpu_usage	32	name=”cpuserver1″

➡️ Each metric can have multiple labels, making Prometheus extremely powerful for filtering and aggregation.

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3️⃣ Why Prometheus is Popular

• Designed for modern microservices
• Excellent label-based querying
• Strong Kubernetes integration
• Simple architecture (no external DB needed)
• Large exporter ecosystem

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4️⃣ Architecture & Core Components of Prometheus

🔹 1. Prometheus Server

This is the heart of the system.

It includes:

• Time-Series Database (TSDB)
• PromQL Engine – query language
• Alerting Rules Engine
• Web UI (Expression Browser)
• Pull Mechanism (scrapes metrics)

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🔹 2. Exporters

Exporters expose metrics in a Prometheus-friendly format.

Examples:

• Node Exporter – Linux OS metrics
• Blackbox Exporter – HTTP, ICMP, TCP checks
• MySQL Exporter
• Nginx Exporter

📌 Exporters run on targets, not on Prometheus itself.

📘 Official exporter list:
https://prometheus.io/docs/instrumenting/exporters/

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🔹 3. Client Libraries

Used when applications expose their own metrics.

Supported languages:

• Go
• Java
• Python
• Node.js
• .NET

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🔹 4. Alertmanager

Handles alerts sent by Prometheus.

Functions:

• Deduplication
• Grouping
• Routing
• Notifications (Email, Slack, PagerDuty, etc.)

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5️⃣ How Prometheus Works (Pull vs Push)

Pull-Based Model (Default)

• Prometheus pulls metrics from targets
• Targets expose /metrics
• Prometheus decides:
  • When to scrape
  • How often
  • Which targets

✅ Better control
✅ Easier debugging
✅ Secure & scalable

⚠️ Push is only used in special cases (via Pushgateway)

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6️⃣ Getting Started – Hands-On Setup

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✅ Step 1: Install & Start Prometheus Server (DONE)

Download:
https://prometheus.io/download/

Reference Guide:
https://www.devopsschool.com/blog/install-and-configure-prometheus-server-and-node-exporter-in-rhel/

Access Prometheus UI:

http://43.205.98.212:9090

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✅ Step 2: Setup Node Exporter on Linux Servers (DONE)

Node Exporter exposes system metrics like:

• CPU
• Memory
• Disk
• Network
• Load

Example metrics endpoint:

http://43.205.98.212:9100/metrics

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✅ Step 3: Configure Scraping for Linux Servers

Targets:

http://43.205.98.212:9100
http://43.205.98.213:9100
http://43.205.98.214:9100

🔧 Add Linux Job in prometheus.yml

scrape_configs:
  - job_name: "linux-nodes"
    static_configs:
      - targets:
          - "43.205.98.212:9100"
          - "43.205.98.213:9100"
          - "43.205.98.214:9100"
        labels:
          env: "production"
          role: "linux-server"

Reload Prometheus:

kill -HUP <prometheus_pid>

or restart service.

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✅ Step 4: Visualize Metrics Using Expression Browser

Open:

http://43.205.98.212:9090

Example PromQL Queries

CPU Usage

rate(node_cpu_seconds_total{mode!="idle"}[5m])

Memory Usage

node_memory_MemAvailable_bytes

Disk Usage

node_filesystem_avail_bytes

📘 PromQL Examples:

• https://www.devopsschool.com/blog/prometheus-promql-example-query/
• https://www.devopsschool.com/blog/prometheus-promql-example-query-node-exporter/

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7️⃣ Summary – Prometheus at a Glance

Feature	Description
Storage	Built-in Time-Series DB
Data Model	Metric + Labels
Collection	Pull-based
Query Language	PromQL
Visualization	Built-in UI + Grafana
Alerts	Prometheus + Alertmanager
Cloud Native	Kubernetes native

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8️⃣ What to Learn Next 🚀

• PromQL (Advanced queries)
• Alert Rules & Alertmanager
• Grafana Dashboards
• Prometheus in Kubernetes
• Federation & Remote Storage

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