LogProx

HTTP proxy with conditional logging and request control

Why?!

At a previous company there was an external API we integrated with. Its versioning strategy was somewhat aggressive and we would incur penalties for accessing deprecated API versions. The idea for logprox was born out of that restriction. Old API calls (sometimes saved on someone's machine, test calls, etc) would potentially put the company at risk. If all calls were proxied through a logging mechanism, not only could we determine where the deprecated calls were coming from, we could block those calls entirely.

Quick Start

Installation

# Build from source
git clone https://github.com/bryan-lott/logprox.git
cd logprox
cargo build --release

Basic Usage

# Start with default config
./target/release/logprox

# Specify custom config
./target/release/logprox --config my-config.yaml

# Set environment variables
PORT=8080 CONFIG_FILE=config.yaml ./target/release/logprox

Simple Example

Create config.yaml:

logging:
  default: false
  rules:
    - name: "Monitor API calls"
      match_conditions:
        path:
          patterns: ["/api/.*"]
      capture:
        method: true
        path: true
        timing: true

Start LogProx and test:

# Proxy format: http://host:port/https://upstream-domain/path
curl -X GET "http://localhost:3000/https://httpbin.org/api/test"

Features

• Conditional Logging: Log requests based on path, method, headers, body
• Request Control: Drop requests based on configurable rules
• Hot Reload: Update configuration without restarting
• Built-in Monitoring: Health checks and configuration endpoints

Architecture

┌─────────────┐    ┌───────────┐    ┌────────────────┐
│   Client    │───▶│  LogProx  │───▶│  Upstream API  │
│ Application │    │           │    │                │
└─────────────┘    └───────────┘    └────────────────┘
                         │
                         ▼
                   ┌────────────┐
                   │   Logs &   │
                   │  Metrics   │
                   └────────────┘

Configuration

LogProx uses YAML configuration with environment variable support (${VAR_NAME}).

Environment Variables

Variable	Default	Description
PORT	3000	Server port
CONFIG_FILE	config.yaml	Configuration file path

Quick Reference

logging:
  default: false
  rules:
    - name: "API Monitoring"
      match_conditions:
        path: { patterns: ["/api/.*"] }
        methods: ["POST", "PUT"]
      capture: { method: true, path: true, timing: true }

drop:
  default: false
  rules:
    - name: "Block Bots"
      match_conditions:
        headers: { "user-agent": ".*bot.*" }
      response: { status_code: 403, body: "Access denied" }

response_logging:
  default: false
  rules:
    - name: "Log Errors"
      match_conditions:
        status_codes: [400, 401, 403, 404, 500, 502, 503]
      capture: { status_code: true, timing: true }

Request Format

Proxy requests use URL path encoding:

http://localhost:3000/https://api.example.com/users/123
                    ↑
                    Encoded upstream URL

Pattern Matching

Regex Examples:

• .* - Match any characters
• ^/api/ - Match paths starting with /api/
• \d+ - Match one or more digits
• (option1|option2) - Match either option

Matching Logic:

• Path patterns: At least one must match
• Methods: Must be in methods list (if specified)
• Headers: All specified headers must match
• Body patterns: At least one must match
• Rule evaluation: First match wins

API Reference

Endpoint	Method	Response
/health	GET	200 OK with body "OK"
/config	GET	Current JSON configuration
/config/docs	GET	Configuration documentation
/config/reload	POST	Reload configuration

Usage Examples

# Health check
curl http://localhost:3000/health

# Get current config
curl http://localhost:3000/config | jq .

# Reload configuration
curl -X POST http://localhost:3000/config/reload

# View documentation
curl http://localhost:3000/config/docs

Troubleshooting

Configuration Issues

# Validate YAML syntax
yamllint config.yaml

# Enable debug logging
RUST_LOG=debug ./target/release/logprox

Common Problems

• Invalid proxy format: Use /https://domain/path format
• Regex errors: Test patterns with regex debugger
• Permission denied: Check config file permissions

Performance

Per-Request Latency

Metric	Time
Average proxy overhead	~3ms
Direct upstream (local)	22ms
Proxied request (local)	25ms

Running Benchmarks

# Micro-benchmarks
cargo bench --bench performance_microbenchmarks

# Comprehensive benchmarks
cargo bench --bench comprehensive_performance

Micro-benchmark Highlights

Operation	Time
Cached regex lookup	10-27 ns
Header iteration (6 headers)	15 ns
Config lock (single)	14 ns
String operations (optimized)	17 ns
YAML config parsing	10 µs

License

GNU GPLv3 © Bryan Lott