Documentation: Add Changelog Entry for v0.4.0 Release

[corylanou]

Documentation: Add Changelog Entry for v0.4.0 Release

Overview

The AWS SDK v2 upgrade (PR #683) represents a significant improvement to Litestream's S3 functionality. This needs to be properly documented in the changelog for the upcoming v0.4.0 release.

Problem

Users need to be informed about:

• The AWS SDK upgrade and its benefits
• New configuration options available
• Performance improvements
• Any migration considerations

Proposed Changelog Entry

## [0.4.0] - 2025-XX-XX

### Major Improvements

#### AWS SDK v2 Upgrade
Litestream now uses AWS SDK for Go v2 for all S3 operations, bringing significant improvements in performance, reliability, and functionality.

**Benefits:**
- **Better Performance**: Connection pooling and optimized HTTP client reduce latency
- **Improved Reliability**: Adaptive retry logic with exponential backoff (up to 10 attempts)
- **Enhanced Security**: Automatic CRC32 checksum validation for data integrity
- **Modern Authentication**: Better support for IAM roles, assume role, and credential chains
- **Reduced Memory Usage**: More efficient memory management for large uploads

**New Configuration Options:**
- `http-timeout`: Configure total timeout for S3 operations (default: 24h)
- `part-size`: Set multipart upload part size (default: 5MB, min: 5MB)
- `concurrency`: Control parallel part uploads (default: 5)

**Example Configuration:**
```yaml
replicas:
  - type: s3
    bucket: my-bucket
    path: my-database
    region: us-east-1
    
    # New performance options
    part-size: 20MB      # Larger parts for big databases
    concurrency: 10      # More parallel uploads
    http-timeout: 6h    # Custom timeout

Improvements

• S3 Error Handling: More descriptive error messages with operation context
• S3-Compatible Services: Better support for MinIO, Wasabi, and other S3-compatible storage
• Configuration Validation: Clearer error messages for misconfigured S3 settings
• Performance: Multipart uploads now configurable for optimal throughput
• Testing: Comprehensive test coverage for S3 operations including error scenarios

Bug Fixes

• Fixed S3 region detection when using IAM roles
• Improved handling of S3 bucket validation errors
• Better error reporting for authentication failures

Internal Changes

• Migrated from github.com/aws/aws-sdk-go to github.com/aws/aws-sdk-go-v2
• Updated S3 client to use AWS SDK v2 configuration patterns
• Improved test infrastructure for S3 integration testing
• Added adaptive testing for moto mock server vs real S3

Compatibility

• No Breaking Changes: All existing S3 configurations continue to work
• Backward Compatible: No changes required to existing Litestream configurations
• Migration: Automatic - no user action required

Documentation

• Added AWS SDK v2 migration guide
• Added S3-compatible services configuration guide
• Added S3 performance tuning documentation
• Updated example configurations with new options

Known Issues

• Multipart upload testing with moto requires workaround for checksum validation (tracked in Update S3 multipart upload test once moto issue #8762 is resolved #700)

Contributors

Thanks to @corylanou for the AWS SDK v2 upgrade implementation and comprehensive testing improvements.

Upgrading

No configuration changes required. To use new performance options:

1. Update to v0.4.0:

   # Docker
   docker pull litestream/litestream:0.4.0
   
   # Binary
   wget https://github.com/benbjohnson/litestream/releases/download/v0.4.0/litestream-v0.4.0-linux-amd64.tar.gz

2. (Optional) Add performance tuning:

   replicas:
     - type: s3
       part-size: 20MB
       concurrency: 10

3. Restart Litestream service

References

• PR feat: upgrade AWS SDK from v1 to v2 for S3 client #683: AWS SDK v2 Upgrade
• Issue Update S3 multipart upload test once moto issue #8762 is resolved #700: Moto multipart upload test tracking
• AWS SDK v2 Documentation: https://aws.github.io/aws-sdk-go-v2/

### Additional Release Notes Sections to Update

#### README.md Updates
```markdown
### What's New in v0.4.0

- **AWS SDK v2**: Improved S3 performance and reliability
- **Configurable Multipart Uploads**: Tune S3 uploads for your needs
- **Better S3-Compatible Support**: Enhanced compatibility with MinIO, Wasabi, etc.

Documentation Site Updates

• Add banner announcing v0.4.0 with SDK v2 improvements
• Update S3 configuration page with new options
• Add performance tuning guide to navigation

Implementation Steps

1. Add changelog entry to CHANGELOG.md
2. Update README.md with version highlights
3. Create GitHub release with detailed notes
4. Update documentation site with new version
5. Announce in Litestream Slack channel

Priority

High - Required for v0.4.0 release

Labels

• documentation
• changelog
• release
• v0.4.0