Validator Transaction Processor

A simplified Solana-inspired transaction validator written in Go.
It demonstrates real-time batching, conflict handling, state snapshots, and UDP/HTTP communication between client and server. This project is meant as an educational exploration of validator design and can serve as a base for experimenting with distributed systems and blockchain-style transaction flow.

Background

The design draws inspiration from Solana’s Agave validator. Alongside the code, I have written a breakdown of the leader phase — covering responsibilities such as Banking Stage, Scheduler, Proof-of-History (PoH) integration, transaction execution, and commitment pipeline.

See: leader-phase/leader-phase.md

Features

• Listens for transactions on UDP port 2001
• Batches incoming transactions (up to 100 at a time)
• Posts each batch to an HTTP server (simulating downstream consumers)
• Applies valid transactions locally with fee deduction and balance mutation
• Generates snapshots of account balances after each batch
• Logs real-time statistics such as transaction counts, fee accumulation, and invalid counts

Project Structure

• main.go – Entry point, bootstraps handler, processor, and batch sender
• processor/ – Core logic for validation, application, and batching
• models/transactions.go – Transaction structure and input parsing
• test/send_tx.go – Sends test transactions to UDP port 2001
• test_server/server.go – Simple HTTP batch receiver (port 2002)
• scripts/ – Build and run scripts
• Makefile – Common automation for build, run, test, reset

Getting Started

Prerequisites

• Go 1.20+
• Linux or macOS
• make, lsof, and kill utilities

Install Go

Install Go (example for macOS with Homebrew):

brew install go

Clone and Setup

git clone https://github.com/<your-username>/validator-transaction-processor.git
cd validator-transaction-processor
go mod tidy

Provide Initial Snapshot

Place your starting account balances in the root as accounts.json.

Run Everything

make full

This builds the validator, starts the HTTP server, and launches the validator.

Send Test Transactions

make test

Reset Environment

make reset
make clean

Transaction Format

Example JSON transaction:

{
  "fee": { "payer": "alice", "amount": 3 },
  "instructions": [
    { "account": "bob", "change": 5 },
    { "account": "charlie", "change": { "account": "alice", "sign": "minus" } }
  ]
}

Design Decisions

• Conflict Resolution: Transactions that touch the same accounts are deferred to future batches.
• Batching: Max 100 transactions per batch, max 100 batches/sec.
• Loose Coupling: UDP listener, batch sender, and snapshot saver are decoupled with in-memory buffers.
• Logging: Stats logged every 30s.
• Cross-Platform Support: make full adapts for macOS and Linux.

Trade-offs and Future Improvements

• Transactions are held in memory, so a crash drops in-flight transactions. A persistent queue would help.
• Conflict handling is simple (defer only) which may increase latency under contention.
• Ports are hardcoded (2001/2002). Configurable ports would be more flexible.
• No TLS or authentication is provided — suitable for experiments, not production.