/**
 * Metrics Collector - System metrics collection and aggregation
 */
import { EventEmitter } from 'eventemitter3';
import { PerformanceMetrics, OperationResult } from '../types';
export declare class MetricsCollector extends EventEmitter {
    private _metrics;
    private _requestAccumulator;
    private _activeConnections;
    private _queueLength;
    private _prevCpuTimes;
    constructor();
    initialize(): Promise<OperationResult>;
    /** Record a completed request. latencyMs is the end-to-end response time. */
    recordRequest(latencyMs: number, isError?: boolean): void;
    /** Adjust the active connection counter by a delta (e.g. +1 on open, -1 on close). */
    trackConnection(delta: number): void;
    /** Set the current queue length directly. */
    trackQueueLength(length: number): void;
    collectMetrics(): PerformanceMetrics;
    shutdown(): Promise<OperationResult>;
    /** Aggregate tick counts across all CPU cores into a single CpuTimes object. */
    private _aggregateCpuTimes;
    /** Calculate CPU utilisation as a 0-1 value from two CpuTimes snapshots. */
    private _calculateCpuUsage;
}
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