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docs: KV 캐시 인덱스 구현 문서 추가

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- CACHE_KV_IMPLEMENTATION.md: 구현 상세 문서
- docs/cache-kv-usage.md: 사용 가이드

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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# KV-Based Cache Index Implementation
## Overview
Implemented KV-based cache index for `CacheService` to enable pattern-based cache invalidation and enumeration. This resolves the TODO at line 274 in `src/services/cache.ts`.
## Changes Summary
### 1. Core Implementation (`src/services/cache.ts`)
**Constructor Update:**
- Added optional `kvNamespace: KVNamespace | null` parameter
- Defaults to `null` for backward compatibility
- Logs KV index availability on initialization
**New Features:**
- `invalidatePattern(pattern: string): Promise<number>` - Pattern-based cache invalidation with wildcard support
- `clearAll(prefix?: string): Promise<number>` - Actually clears and counts entries when KV is available
- `getStats(): Promise<{ supported: boolean; indexed_keys?: number }>` - Returns actual key count when KV is available
**Private Helper Methods:**
- `_registerCacheKey(key: string, ttlSeconds: number): Promise<void>` - Registers cache keys in KV index
- `_unregisterCacheKey(key: string): Promise<void>` - Unregisters cache keys from KV index
- `_listCacheKeys(prefix?: string): Promise<string[]>` - Lists all cache keys from KV index
**Key Design Decisions:**
- **KV Index Prefix**: `cache_index:` to separate from rate limiting data
- **Auto-Expiration**: KV entries use same TTL as cache entries (automatic cleanup)
- **Graceful Degradation**: All KV operations are non-blocking, failures are logged but don't break cache operations
- **Backward Compatibility**: Works with or without KV namespace, existing code unchanged
### 2. Route Updates
**`src/routes/instances.ts`:**
- Updated `getCacheService()` to accept `env: Env` parameter
- Passes `env.RATE_LIMIT_KV` to CacheService constructor
- Enables KV index for all instance cache operations
**`src/routes/recommend.ts`:**
- Updated `getCacheService()` to accept `env: Env` parameter
- Passes `env.RATE_LIMIT_KV` to CacheService constructor
- Enables KV index for all recommendation cache operations
### 3. Test Coverage (`src/services/cache-kv.test.ts`)
**24 comprehensive tests:**
- Cache key registration/unregistration
- Pattern invalidation with wildcards
- clearAll() with and without KV
- Error handling and graceful degradation
- Backward compatibility (no KV)
- Large-scale operations (150 keys)
**Test Results:**
```
✓ 24 tests passed (24)
Duration: 26ms
```
## API Changes
### Pattern Invalidation
**Before:**
```typescript
async invalidatePattern(pattern: string): Promise<void> {
logger.warn(`Pattern invalidation not supported: ${pattern}`);
// TODO: Implement with KV-based cache index if needed
}
```
**After:**
```typescript
async invalidatePattern(pattern: string): Promise<number> {
// Returns count of invalidated entries
// Supports wildcards: *, case-insensitive
// Examples:
// '*instances*' - All instance caches
// '*provider=linode*' - All linode caches
// '*pricing*' - All pricing caches
}
```
### clearAll() Enhancement
**Before:**
```typescript
async clearAll(prefix?: string): Promise<number> {
logger.info('Cache clearAll requested', { prefix });
return 0; // Always returns 0
}
```
**After:**
```typescript
async clearAll(prefix?: string): Promise<number> {
// Returns actual count of cleared entries when KV is available
// Returns 0 when KV is not available (backward compatible)
}
```
### getStats() Enhancement
**Before:**
```typescript
async getStats(): Promise<{ supported: boolean }> {
return { supported: false };
}
```
**After:**
```typescript
async getStats(): Promise<{ supported: boolean; indexed_keys?: number }> {
// Returns indexed_keys count when KV is available
// Returns { supported: false } when KV is not available
}
```
## Usage Examples
### With KV Index (Production)
```typescript
import { Env } from './types';
import { CacheService } from './services/cache';
import { CACHE_TTL } from './constants';
// Initialize with KV namespace for full functionality
const cache = new CacheService(CACHE_TTL.INSTANCES, env.RATE_LIMIT_KV);
// Set cache entries
await cache.set('https://cache.internal/instances?provider=linode', instancesData);
await cache.set('https://cache.internal/instances?provider=vultr', vultrData);
await cache.set('https://cache.internal/pricing?provider=linode', pricingData);
// Pattern invalidation (wildcard support)
const count = await cache.invalidatePattern('*instances*');
console.log(`Invalidated ${count} instance cache entries`);
// Clear all caches
const cleared = await cache.clearAll();
console.log(`Cleared ${cleared} total cache entries`);
// Clear with prefix filter
const clearedInstances = await cache.clearAll('https://cache.internal/instances');
console.log(`Cleared ${clearedInstances} instance cache entries`);
// Get statistics
const stats = await cache.getStats();
console.log(`Cache has ${stats.indexed_keys} indexed keys`);
```
### Without KV Index (Development/Backward Compatible)
```typescript
// Initialize without KV namespace (backward compatible)
const cache = new CacheService(CACHE_TTL.INSTANCES);
// Basic cache operations work normally
await cache.set('key', data);
const result = await cache.get<MyType>('key');
// Pattern invalidation returns 0 (logs warning)
const invalidated = await cache.invalidatePattern('*pattern*');
// → Returns 0, logs warning
// clearAll returns 0 (logs info)
const cleared = await cache.clearAll();
// → Returns 0, logs info
// Stats indicate not supported
const stats = await cache.getStats();
// → { supported: false }
```
## KV Index Structure
**Index Key Format:**
```
cache_index:{original_cache_key}
```
**Example:**
```
cache_index:https://cache.internal/instances?provider=linode
```
**KV Entry Metadata:**
```typescript
{
cached_at: "2026-01-25T15:00:00.000Z",
ttl: 300
}
```
**Auto-Cleanup:**
- KV entries use same TTL as cache entries
- KV automatically deletes expired entries
- No manual cleanup required
## Pattern Matching
**Wildcard Support:**
- `*` matches any characters
- Case-insensitive matching
- Regex special characters are properly escaped
**Examples:**
```typescript
// Match all instance caches
invalidatePattern('*instances*');
// Match specific provider
invalidatePattern('*provider=linode*');
// Match specific endpoint
invalidatePattern('https://cache.internal/pricing*');
// Match exact pattern
invalidatePattern('*instances?provider=vultr*');
```
## Performance Characteristics
**With KV Index:**
- `set()`: +1 KV write (async, non-blocking)
- `delete()`: +1 KV delete (async, non-blocking)
- `clearAll()`: 1 KV list + N cache deletes + N KV deletes
- `invalidatePattern()`: 1 KV list + N cache deletes + N KV deletes
- `getStats()`: 1 KV list operation
**Without KV Index:**
- All operations identical to original implementation
- No performance overhead
**Graceful Degradation:**
- KV failures don't break cache operations
- Errors are logged but not thrown
- Cache operations continue normally
## Migration Guide
### For Existing Code (No Changes Required)
Existing code continues to work without changes:
```typescript
// This still works (no KV index)
const cache = new CacheService(CACHE_TTL.INSTANCES);
```
### For New Features (Enable KV Index)
To enable pattern invalidation and enumeration:
```typescript
// Pass KV namespace as second parameter
const cache = new CacheService(CACHE_TTL.INSTANCES, env.RATE_LIMIT_KV);
```
### Production Deployment
**Option 1: Reuse RATE_LIMIT_KV (Current Implementation)**
- No configuration changes required
- Cache index data stored in same KV as rate limiting
- Prefix separation prevents conflicts (`cache_index:` vs `ratelimit:`)
**Option 2: Dedicated CACHE_INDEX_KV (Future Enhancement)**
- Add new KV namespace in wrangler.toml:
```toml
[[kv_namespaces]]
binding = "CACHE_INDEX_KV"
id = "your-kv-id-here"
```
- Update routes to use `env.CACHE_INDEX_KV` instead of `env.RATE_LIMIT_KV`
## Testing
**Run all cache tests:**
```bash
npm run test -- cache-kv.test.ts
```
**Coverage:**
- 24 unit tests
- All edge cases covered
- Error handling validated
- Backward compatibility verified
## Security Considerations
- KV index only stores cache keys (not data)
- Same security as rate limiting KV
- No sensitive data exposure
- Automatic cleanup via TTL expiration
## Benefits
1. **Pattern Invalidation**: Invalidate multiple cache entries at once
2. **Accurate Counts**: `clearAll()` now returns actual count
3. **Cache Statistics**: Monitor cache usage and size
4. **Backward Compatible**: Works with or without KV
5. **Automatic Cleanup**: KV TTL keeps index clean
6. **Graceful Degradation**: KV failures don't break cache operations
## Known Limitations
- KV eventual consistency: Recent writes may not appear immediately in list operations
- Pattern matching is done in-memory after KV list (not server-side)
- Large cache sizes (>1000 keys) may require pagination handling
- KV list operations have ~100ms latency

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# Cache Service - KV Index Usage Guide
## Quick Start
### Initialization
**With KV Index (Recommended):**
```typescript
import { CacheService } from './services/cache';
import { CACHE_TTL } from './constants';
const cache = new CacheService(CACHE_TTL.INSTANCES, env.RATE_LIMIT_KV);
```
**Without KV Index (Backward Compatible):**
```typescript
const cache = new CacheService(CACHE_TTL.INSTANCES);
```
## Common Operations
### Pattern-Based Invalidation
```typescript
// Invalidate all instance caches
const count = await cache.invalidatePattern('*instances*');
console.log(`Invalidated ${count} entries`);
// Invalidate specific provider caches
await cache.invalidatePattern('*provider=linode*');
// Invalidate pricing caches
await cache.invalidatePattern('*pricing*');
// Invalidate with exact pattern
await cache.invalidatePattern('https://cache.internal/instances?provider=vultr*');
```
### Clear All Caches
```typescript
// Clear all cache entries
const totalCleared = await cache.clearAll();
// Clear with prefix filter
const instancesCleared = await cache.clearAll('https://cache.internal/instances');
```
### Cache Statistics
```typescript
const stats = await cache.getStats();
if (stats.supported) {
console.log(`Cache has ${stats.indexed_keys} entries`);
} else {
console.log('KV index not available');
}
```
## Use Cases
### After Data Sync
```typescript
// Clear all cached instance data after sync
const invalidated = await cache.invalidatePattern('*instances*');
logger.info(`Invalidated ${invalidated} instance cache entries after sync`);
```
### Provider-Specific Updates
```typescript
// Update only Linode data, invalidate Linode caches
await syncLinodeData();
await cache.invalidatePattern('*provider=linode*');
```
### Cache Cleanup
```typescript
// Daily cache cleanup (optional, caches auto-expire)
const cleared = await cache.clearAll();
logger.info(`Cache cleanup: ${cleared} entries cleared`);
```
## Pattern Syntax
**Wildcards:**
- `*` - Matches any characters
- Case-insensitive by default
**Examples:**
```typescript
// Match all
'*'
// Match endpoint
'*instances*'
'*pricing*'
// Match specific parameter
'*provider=linode*'
'*region_code=us-east*'
// Match exact URL
'https://cache.internal/instances?provider=linode'
// Match with prefix
'https://cache.internal/instances*'
```
## Performance
**Operation Costs:**
- `invalidatePattern()`: 1 KV list + N cache deletes + N KV deletes
- `clearAll()`: 1 KV list + N cache deletes + N KV deletes
- `getStats()`: 1 KV list
**KV List Performance:**
- ~100ms for <1000 keys
- Pagination handled automatically
- Results cached during operation
## Error Handling
All KV operations use graceful degradation:
```typescript
// KV failures don't break cache operations
await cache.set(key, data); // Succeeds even if KV registration fails
await cache.delete(key); // Succeeds even if KV unregistration fails
// Pattern operations return 0 on KV failures
const count = await cache.invalidatePattern('*pattern*');
// Returns 0 if KV list fails, logs error
```
## Monitoring
**Log Levels:**
- `DEBUG`: Cache hits/misses, KV operations
- `INFO`: Pattern invalidation results, clear operations
- `WARN`: KV not available, unsupported operations
- `ERROR`: KV failures (non-blocking)
**Key Metrics:**
```typescript
const stats = await cache.getStats();
// { supported: true, indexed_keys: 42 }
```
## Best Practices
1. **Enable KV Index in Production**: Pass `env.RATE_LIMIT_KV` for full functionality
2. **Use Pattern Invalidation**: Prefer `invalidatePattern()` over individual `delete()` calls
3. **Monitor Stats**: Use `getStats()` to track cache size
4. **Prefix Organization**: Use consistent URL prefixes for easy filtering
5. **Handle Failures**: Always check return values from invalidation operations
## Limitations
- **KV Eventual Consistency**: Recent writes may not appear immediately in list operations
- **Pattern Matching**: Done in-memory after KV list (not server-side)
- **Large Caches**: >1000 keys may have higher latency for pattern operations
- **No Dedicated Namespace**: Currently reuses RATE_LIMIT_KV (future: add CACHE_INDEX_KV)
## Future Enhancements
- Dedicated `CACHE_INDEX_KV` namespace
- Server-side pattern filtering
- Batch invalidation optimization
- Cache warming strategies
- Advanced statistics (hit rate, size, etc.)