Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

0.1.0 - 2025-12-02

Added

Core Features

• Initial implementation of TCC (Try-Confirm-Cancel) protocol
• TCC module with pipe-friendly API
• TCC.Transaction module for transaction coordination
• TCC.Action module for individual action execution
• Support for three-phase transactions: Try, Confirm, Cancel
• Automatic rollback on Try phase failures
• Sequential execution of Try and Confirm phases
• Reverse-order execution of Cancel phase (LIFO)

Reliability Features

• Automatic retry logic for Confirm and Cancel phases with exponential backoff
• Configurable timeout per transaction and per action
• Configurable retry limits (default: 3 retries)
• Idempotency support through retry mechanism
• Effects accumulator for tracking transaction state

Observability

• Telemetry integration with events:
  • [:tcc, :transaction, :start] - Transaction started
  • [:tcc, :transaction, :stop] - Transaction completed
  • [:tcc, :action, :start] - Action phase started
  • [:tcc, :action, :stop] - Action phase completed
  • [:tcc, :action, :exception] - Action phase exception
• Comprehensive metadata for all telemetry events
• Transaction ID generation for tracking

API

• TCC.new/1 - Create new transaction with options
• TCC.run/5 - Add action to transaction
• TCC.run_with_opts/6 - Add action with custom options
• TCC.execute/2 - Execute transaction synchronously
• TCC.async_execute/2 - Execute transaction asynchronously
• TCC.actions/1 - Get list of actions in transaction
• TCC.options/1 - Get transaction options

Configuration Options

• :timeout - Maximum time for entire transaction (default: 30_000ms)
• :retry_limit - Number of retries for confirm/cancel (default: 3)
• :async - Async execution mode (default: false)
• :telemetry_prefix - Custom telemetry event prefix (default: [:tcc])

Documentation

• Comprehensive README with usage examples
• Quick Start Guide (QUICKSTART.md)
• Architecture documentation (ARCHITECTURE.md)
• API documentation with @moduledoc and @doc
• Doctests for core functionality

Examples

• examples/simple_transfer.ex - Money transfer between accounts with in-memory database
• examples/e_commerce.ex - Complete e-commerce order processing:
  • Payment service with reservation and confirmation
  • Inventory management
  • Shipping arrangement
• examples/demo.exs - Interactive demo script

Testing

• Comprehensive test suite with ExUnit
• Unit tests for TCC, Transaction, and Action modules
• Integration tests for complete transaction flows
• Test coverage for:
  • Successful transactions
  • Failed transactions with rollback
  • Effects accumulation
  • Retry logic
  • Concurrent execution
  • Custom options

Technical Details

Dependencies

• telemetry ~> 1.0 - For observability
• ex_doc ~> 0.29 - For documentation generation (dev only)

Inspired By

• Apache Seata's TCC mode for protocol design
• Sage library for API design patterns
• Industry best practices for distributed transactions

Known Limitations

• Sequential execution only (no parallel Try operations)
• No persistent transaction log (in-memory only)
• No distributed coordinator (local transactions only)
• No automatic timeout deadline enforcement across all actions

Breaking Changes

• N/A (initial release)

Deprecated

• N/A (initial release)

Security

• No known security issues
• Timeout limits prevent resource exhaustion
• No sensitive data logged in telemetry by default

[Unreleased]

Planned Features

• Parallel execution of independent Try operations
• Persistent transaction log for audit and recovery
• Distributed transaction coordinator support
• Saga pattern integration
• Circuit breaker integration
• Transaction visualization tools
• Enhanced error recovery mechanisms
• Automatic deadline management
• Performance benchmarks