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Changelog

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

[0.4.1] - 2025-12-28

Changed

  • Updated crucible_framework dependency from ~> 0.5.0 to ~> 0.5.2
  • Updated telemetry dependency from ~> 1.2 to ~> 1.3
  • Updated postgrex dependency from >= 0.0.0 to >= 0.21.1
  • Updated supertester dependency from ~> 0.3.1 to ~> 0.4.0

[0.4.0] - 2025-12-26

Changed

  • Canonical Schema Format: Normalized describe/1 to the canonical schema format as defined in the Stage Describe Contract specification v1.0.0
    • Changed :stage key to :name key (atom value)
    • Added required, optional, types, defaults fields for option validation
    • Moved inputs/outputs to __extensions__.hedging namespace
    • Added schema version marker (__schema_version__: "1.0.0")
  • Updated crucible_framework dependency from ~> 0.4.0 to ~> 0.5.0

Added

  • Conformance Tests: New test/crucible_hedging/conformance_test.exs verifying stage contract compliance
  • Stage Contract Documentation: Added Stage Contract section to README.md with schema introspection examples
  • Type specifications for all options in the canonical format

Documentation

  • Updated README.md with Stage Contract section documenting required/optional options
  • Added schema introspection code examples

[0.3.0] - 2025-12-25

Added

  • Crucible Framework Integration: Added CrucibleHedging.CrucibleStage module implementing Crucible.Stage behaviour for seamless pipeline integration
    • Proper Crucible.Context handling with artifacts and metrics storage
    • Stage completion tracking with mark_stage_complete/2
    • Support for all hedging strategies through IR configuration
    • Comprehensive error handling and validation
  • Enhanced SVG Logo: Updated assets/crucible_hedging.svg with speed-themed racing design featuring parallel paths and finish line visualization
  • Configuration Management: Added config/config.exs to disable CrucibleFramework.Repo (hedging doesn't need database persistence)
  • Documentation: Added comprehensive documentation in docs/20251225/:
    • current_state.md - Complete module inventory and architecture documentation
    • gaps.md - Gap analysis and future improvements
    • implementation_prompt.md - Detailed implementation guide

Changed

  • Updated crucible_ir dependency from ~> 0.1.1 to ~> 0.2.0
  • Added crucible_framework ~> 0.4.0 dependency for Stage behaviour support
  • Enhanced race condition handling in core hedging logic with monotonic completion ordering
  • Improved code quality with Credo integration
  • Updated README.md with Crucible Framework integration examples

Fixed

  • Race condition in find_first_result/1 by using both completion time and monotonic completion order
  • Metrics calculation edge cases for empty latency lists
  • Multi-level hedging pending task updates
  • Code style improvements for Credo compliance
  • Enhanced test reliability with supertester for proper isolation

Dependencies

  • Added crucible_framework ~> 0.4.0 for pipeline integration
  • Added ecto_sql ~> 3.11 (optional, for framework compatibility)
  • Added postgrex >= 0.0.0 (optional, for framework compatibility)
  • Added supertester ~> 0.3.1 for improved test isolation
  • Added stream_data ~> 1.0 for property-based testing support
  • Added credo ~> 1.7 for code quality analysis

[0.2.1] - 2025-11-26 (unreleased)

Added

  • CrucibleIR Integration: Added dependency on crucible_ir ~> 0.1.1 for unified configuration
  • Pipeline Stage Interface: New CrucibleHedging.Stage module implementing pipeline stage pattern
    • Accepts CrucibleIR.Reliability.Hedging configuration from experiment context
    • Provides run/2 and describe/1 functions for pipeline integration
    • Supports all hedging strategies through IR configuration
    • Returns structured context with results and metadata
  • IR Config Helper: New from_ir_config/1 function to convert IR structs to keyword options
  • Strategy Options Mapping: Support for strategy-specific options from IR config options map
  • Comprehensive Stage Tests: Full test coverage for Stage module with all strategies

Enhanced

  • Main CrucibleHedging module now supports IR config conversion
  • Stage module provides detailed metadata including strategy used
  • Error handling for missing or invalid IR configurations
  • Documentation with IR config usage examples

Documentation

  • Added Stage usage examples to README
  • Documented IR config integration patterns
  • Added docstrings for all new public functions

[0.2.0] - 2025-11-25

Added

  • Exponential Backoff Strategy: New adaptive strategy that adjusts hedge delay based on success/failure patterns
    • Decreases delay on successful hedges (multiplicative decrease)
    • Increases delay on failed hedges and errors (multiplicative increase)
    • Configurable min/max bounds and adjustment factors
    • Ideal for rate-limited APIs and services with variable health
  • Strategy naming support to isolate per-backend backoff state
  • Enhanced configuration validation for exponential backoff parameters
  • Comprehensive test suite for exponential backoff strategy with 100% coverage
  • Strategy statistics tracking (consecutive successes/failures, total adjustments)
  • Reset capability for exponential backoff strategy

Enhanced

  • Updated CrucibleHedging.Strategy to register exponential_backoff strategy
  • Added exponential backoff configuration options to CrucibleHedging.Config
  • Enhanced documentation with exponential backoff usage examples
  • Added validation for exponential backoff configuration parameters
  • Strategies now react to error outcomes so exponential backoff can increase delay on failures

Documentation

  • Comprehensive design document in docs/20251125/enhancement_design.md
  • Updated README.md with exponential backoff strategy section
  • Added usage examples and algorithm description
  • Documented configuration options and validation rules

Research Foundation

  • Based on TCP congestion control (AIMD - Additive Increase Multiplicative Decrease)
  • Implements exponential backoff patterns from distributed systems

[0.1.0] - 2025-10-07

Added

  • Initial release
  • Request hedging for tail latency reduction in distributed systems
  • Multiple hedging strategies (fixed, percentile-based, adaptive with Thompson Sampling, workload-aware)
  • Multi-tier hedging with cascade across providers for cost optimization
  • Adaptive learning with online optimization to minimize regret
  • Budget-aware hedging with comprehensive cost tracking
  • Rich telemetry integration with detailed observability
  • Production-ready implementation with lightweight GenServers and proper supervision

Documentation

  • Comprehensive README with examples
  • API documentation for all hedging strategies
  • Usage examples for LLM inference optimization
  • Research foundation based on Google's "The Tail at Scale" paper
  • Performance benchmarks showing 75-96% P99 latency reduction