/**
 * Simple file-based metrics collector for DuckDB MCP
 *
 * Collects performance metrics and writes them to rotating JSON log files
 * without external dependencies like Prometheus or Grafana.
 */
/**
 * Performance metrics as defined in the roadmap
 */
export interface PerformanceMetrics {
    queryTime: number;
    memoryUsage: number;
    connectionPoolHitRate: number;
    cacheHitRate: number;
    spaceIsolation: boolean;
}
/**
 * Query metric entry
 */
export interface QueryMetric {
    timestamp: string;
    sql: string;
    executionTimeMs: number;
    rowCount: number;
    isSimple: boolean;
    spaceId?: string;
}
/**
 * Memory metric entry
 */
export interface MemoryMetric {
    timestamp: string;
    heapUsed: number;
    heapTotal: number;
    external: number;
    arrayBuffers: number;
    totalMB: number;
}
/**
 * Connection pool metric
 */
export interface ConnectionMetric {
    timestamp: string;
    totalConnections: number;
    activeConnections: number;
    hitCount: number;
    missCount: number;
    hitRate: number;
}
/**
 * Cache metric
 */
export interface CacheMetric {
    timestamp: string;
    totalRequests: number;
    hits: number;
    misses: number;
    hitRate: number;
    entriesCount: number;
}
/**
 * Metrics collector configuration
 */
interface MetricsConfig {
    logsDir: string;
    rotationInterval: number;
    flushInterval: number;
    maxFileSize: number;
    retentionDays: number;
}
export declare class MetricsCollector {
    private config;
    private queryBuffer;
    private memoryBuffer;
    private connectionBuffer;
    private cacheBuffer;
    private flushTimer?;
    private memoryTimer?;
    private queryCount;
    private cacheHits;
    private cacheMisses;
    private connectionHits;
    private connectionMisses;
    constructor(config?: Partial<MetricsConfig>);
    /**
     * Start collecting metrics
     */
    start(): Promise<void>;
    /**
     * Stop collecting metrics
     */
    stop(): Promise<void>;
    /**
     * Record a query execution
     */
    recordQuery(sql: string, executionTimeMs: number, rowCount: number, spaceId?: string): void;
    /**
     * Record connection pool access
     */
    recordConnectionPoolAccess(hit: boolean, stats: {
        totalConnections: number;
        activeConnections: number;
    }): void;
    /**
     * Record cache access
     */
    recordCacheAccess(hit: boolean, entriesCount: number): void;
    /**
     * Collect memory metrics
     */
    private collectMemoryMetrics;
    /**
     * Get current performance summary
     */
    getPerformanceSummary(): Promise<PerformanceMetrics>;
    /**
     * Flush metrics to disk
     */
    private flush;
    /**
     * Write metrics to file (append mode)
     */
    private writeMetrics;
    /**
     * Rotate large files
     */
    private rotateFile;
    /**
     * Clean old log files
     */
    private cleanOldLogs;
    /**
     * Ensure log directory exists
     */
    private ensureLogDir;
    /**
     * Get metrics for a specific date range
     */
    getMetrics(startDate: string, endDate: string, type: 'queries' | 'memory' | 'connections' | 'cache'): Promise<any[]>;
}
/**
 * Get or create the metrics collector instance
 */
export declare function getMetricsCollector(): MetricsCollector;
export {};
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