feat: add namespace and epoch for enhancement.

[AminMortezaie]

Add Namespace and Epoch Support to KV Store

Overview

This PR introduces namespace and epoch support to AutoMQ's KV store system through a composable design pattern, allowing for backward compatibility while providing new functionality for applications that need namespace isolation and epoch-based versioning.

Key Changes

1. Added a new NamespacedControllerKVClient that extends the base ControllerKVClient
2. Introduced a feature flag namespacedKVEnabled in Config for opt-in functionality
3. Modified DefaultS3Client to support both namespaced and non-namespaced modes

Implementation Details

• Namespace Support: Keys are prefixed with their namespace (e.g., "namespace:key") for isolation
• Epoch Management: Each namespace maintains its own epoch counter for versioning
• Backward Compatibility:
  • Default behavior remains unchanged (namespacedKVEnabled = false)
  • Existing applications continue to work without modification
  • New applications can opt-in to namespaced functionality

Usage

To enable namespaced KV operations:

Config config = new Config()
    .namespacedKVEnabled(true);

When enabled, applications can:

• Use namespace isolation for keys
• Maintain epoch versioning per namespace
• Prevent cross-namespace conflicts
• Maintain data isolation between different parts of the system

Migration Path

1. Deploy the changes with namespacedKVEnabled = false (default)
2. Applications can gradually opt-in to namespaced functionality
3. No immediate action required for existing applications

Performance Impact

• Minimal overhead for non-namespaced operations (no changes to existing path)
• Small additional overhead for namespaced operations:
  • Key prefix addition
  • Epoch checks
  • Additional epoch storage per namespace

Future Considerations

1. Namespace cleanup utilities
2. Epoch management tools
3. Namespace statistics and monitoring
4. Cross-namespace operations (if needed)

Related Issue

• [Issue [Enhancement] Enhance KVRecord #2343 ] [Enhancement] Enhance KVRecord

[CLAassistant]

All committers have signed the CLA.

[superhx]

@AminMortezaie We sincerely appreciate your contributions. However, it appears that there might be a misunderstanding regarding the requirement. Instead of manipulating the key field, what we actually need is to extend the KVRecord by adding two new fields: namespace and epoch.

• With namespace field, we can fast filter the KVs in certain namespace instead of matching them by prefix.

[AminMortezaie]

Great, I will change to the real requirements.