# Monitor Gateway

# Overview

The Monitor Gateway is a read-only API service that provides secure access to engine data for monitoring and observability purposes. Unlike the Control Gateway, which requires administrative access and bidirectional communication, the Monitor Gateway exposes only read-only endpoints and operates with the engine initiating the connection.

# Key Features

Read-Only Access: Exposes only safe, read-only API endpoints
Outbound Engine Connection: Engine connects outward to the monitor gateway for enhanced security
Separate Docker Image: Deployed independently from other gateway components
Monitoring Focus: Designed specifically for observability and monitoring use cases

# Architecture

# Network Communication Pattern

The Monitor Gateway uses a reverse connection pattern compared to the Control Gateway:

Control Gateway: Connects inward to the engine (gateway → engine)
Monitor Gateway: Engine connects outward to the gateway (engine → monitor gateway)

This design provides several security benefits:

Monitor gateway can be placed in a less trusted network zone
Engine maintains control over the connection lifecycle
Reduces attack surface for administrative operations

# Connection Flow

flowchart LR
    subgraph "Trusted Zone"
        engine["Engine"]
    end
    
    subgraph "Monitoring Zone"
        monitor["Monitor Gateway"]
        grafana["Grafana"]
        prometheus["Prometheus"]
    end
    
    engine -->|Outbound TCP| monitor
    prometheus -->|HTTP| monitor
    grafana -->|HTTP| monitor
    
    style engine fill:#ff9999
    style monitor fill:#99ccff

# Configuration

# Environment Variables

To deploy the monitor gateway, both the engine and monitor gateway require the following environment variables:

environment:
  - MONITOR_GATEWAY_HOSTNAME=monitor-gateway
  - MONITOR_GATEWAY_ENGINE_PORT=8182
  - MONITOR_GATEWAY_REST_PORT=8081

Without these variables defined, the engine will not initiate a connection to the monitor gateway, and the monitor gateway itself will not start.

# Resource Requirements

Minimum Requirements:

1 GB RAM
1 CPU core

Recommended for Production:

2-4 GB RAM
2 CPU cores