feat(cache): add cache health monitoring and validation system, see #730

- Add cache entry validator service for data integrity checks
- Add cache health monitor service for periodic health checks
- Enhance model cache and scanner with validation support
- Update websocket manager for health status broadcasting
- Add initialization banner service for cache health alerts
- Add comprehensive test coverage for new services
- Update translations across all locales
- Refactor sync translation keys script

py/services/cache_health_monitor.py

@@ -0,0 +1,201 @@
+"""
+Cache Health Monitor
+
+Monitors cache health status and determines when user intervention is needed.
+"""
+
+from dataclasses import dataclass, field
+from enum import Enum
+from typing import Any, Dict, List, Optional
+import logging
+
+from .cache_entry_validator import CacheEntryValidator, ValidationResult
+
+logger = logging.getLogger(__name__)
+
+
+class CacheHealthStatus(Enum):
+    """Health status of the cache."""
+    HEALTHY = "healthy"
+    DEGRADED = "degraded"
+    CORRUPTED = "corrupted"
+
+
+@dataclass
+class HealthReport:
+    """Report of cache health check."""
+    status: CacheHealthStatus
+    total_entries: int
+    valid_entries: int
+    invalid_entries: int
+    repaired_entries: int
+    invalid_paths: List[str] = field(default_factory=list)
+    message: str = ""
+
+    @property
+    def corruption_rate(self) -> float:
+        """Calculate the percentage of invalid entries."""
+        if self.total_entries <= 0:
+            return 0.0
+        return self.invalid_entries / self.total_entries
+
+    def to_dict(self) -> Dict[str, Any]:
+        """Convert to dictionary for JSON serialization."""
+        return {
+            'status': self.status.value,
+            'total_entries': self.total_entries,
+            'valid_entries': self.valid_entries,
+            'invalid_entries': self.invalid_entries,
+            'repaired_entries': self.repaired_entries,
+            'corruption_rate': f"{self.corruption_rate:.1%}",
+            'invalid_paths': self.invalid_paths[:10],  # Limit to first 10
+            'message': self.message,
+        }
+
+
+class CacheHealthMonitor:
+    """
+    Monitors cache health and determines appropriate status.
+
+    Thresholds:
+    - HEALTHY: 0% invalid entries
+    - DEGRADED: 0-5% invalid entries (auto-repaired, user should rebuild)
+    - CORRUPTED: >5% invalid entries (significant data loss likely)
+    """
+
+    # Threshold percentages
+    DEGRADED_THRESHOLD = 0.01   # 1% - show warning
+    CORRUPTED_THRESHOLD = 0.05  # 5% - critical warning
+
+    def __init__(
+        self,
+        *,
+        degraded_threshold: float = DEGRADED_THRESHOLD,
+        corrupted_threshold: float = CORRUPTED_THRESHOLD
+    ):
+        """
+        Initialize the health monitor.
+
+        Args:
+            degraded_threshold: Corruption rate threshold for DEGRADED status
+            corrupted_threshold: Corruption rate threshold for CORRUPTED status
+        """
+        self.degraded_threshold = degraded_threshold
+        self.corrupted_threshold = corrupted_threshold
+
+    def check_health(
+        self,
+        entries: List[Dict[str, Any]],
+        *,
+        auto_repair: bool = True
+    ) -> HealthReport:
+        """
+        Check the health of cache entries.
+
+        Args:
+            entries: List of cache entry dictionaries to check
+            auto_repair: If True, attempt to repair entries during validation
+
+        Returns:
+            HealthReport with status and statistics
+        """
+        if not entries:
+            return HealthReport(
+                status=CacheHealthStatus.HEALTHY,
+                total_entries=0,
+                valid_entries=0,
+                invalid_entries=0,
+                repaired_entries=0,
+                message="Cache is empty"
+            )
+
+        total_entries = len(entries)
+        valid_entries: List[Dict[str, Any]] = []
+        invalid_entries: List[Dict[str, Any]] = []
+        repaired_count = 0
+        invalid_paths: List[str] = []
+
+        for entry in entries:
+            result = CacheEntryValidator.validate(entry, auto_repair=auto_repair)
+
+            if result.is_valid:
+                valid_entries.append(result.entry if result.entry else entry)
+                if result.repaired:
+                    repaired_count += 1
+            else:
+                invalid_entries.append(entry)
+                # Extract file path for reporting
+                file_path = CacheEntryValidator.get_file_path_safe(entry, '<unknown>')
+                invalid_paths.append(file_path)
+
+        invalid_count = len(invalid_entries)
+        valid_count = len(valid_entries)
+
+        # Determine status based on corruption rate
+        corruption_rate = invalid_count / total_entries if total_entries > 0 else 0.0
+
+        if invalid_count == 0:
+            status = CacheHealthStatus.HEALTHY
+            message = "Cache is healthy"
+        elif corruption_rate >= self.corrupted_threshold:
+            status = CacheHealthStatus.CORRUPTED
+            message = (
+                f"Cache is corrupted: {invalid_count} invalid entries "
+                f"({corruption_rate:.1%}). Rebuild recommended."
+            )
+        elif corruption_rate >= self.degraded_threshold or invalid_count > 0:
+            status = CacheHealthStatus.DEGRADED
+            message = (
+                f"Cache has {invalid_count} invalid entries "
+                f"({corruption_rate:.1%}). Consider rebuilding cache."
+            )
+        else:
+            # This shouldn't happen, but handle gracefully
+            status = CacheHealthStatus.HEALTHY
+            message = "Cache is healthy"
+
+        # Log the health check result
+        if status != CacheHealthStatus.HEALTHY:
+            logger.warning(
+                f"Cache health check: {status.value} - "
+                f"{invalid_count}/{total_entries} invalid, "
+                f"{repaired_count} repaired"
+            )
+            if invalid_paths:
+                logger.debug(f"Invalid entry paths: {invalid_paths[:5]}")
+
+        return HealthReport(
+            status=status,
+            total_entries=total_entries,
+            valid_entries=valid_count,
+            invalid_entries=invalid_count,
+            repaired_entries=repaired_count,
+            invalid_paths=invalid_paths,
+            message=message
+        )
+
+    def should_notify_user(self, report: HealthReport) -> bool:
+        """
+        Determine if the user should be notified about cache health.
+
+        Args:
+            report: The health report to evaluate
+
+        Returns:
+            True if user should be notified
+        """
+        return report.status != CacheHealthStatus.HEALTHY
+
+    def get_notification_severity(self, report: HealthReport) -> str:
+        """
+        Get the severity level for user notification.
+
+        Args:
+            report: The health report to evaluate
+
+        Returns:
+            Severity string: 'warning' or 'error'
+        """
+        if report.status == CacheHealthStatus.CORRUPTED:
+            return 'error'
+        return 'warning'