/**
 * Resilient Exporter
 *
 * Wrapper that ensures Tier 2/3 export failures never block core request paths.
 * Export failures are observable via metrics, not via blocking or exceptions.
 */
import type { SpanExporter, ReadableSpan } from "@opentelemetry/sdk-trace-base";
import { ExportResult } from "@opentelemetry/core";
/**
 * Configuration for the resilient exporter.
 */
export interface ResilientExporterConfig {
    /** Underlying exporter to wrap */
    delegate: SpanExporter;
    /** Max items to buffer before dropping (default: 2048) */
    maxQueueSize?: number;
    /** Export timeout in ms (default: 30000) */
    exportTimeoutMs?: number;
    /** Callback when items are dropped due to backpressure */
    onDrop?: (count: number, reason: "queue_full" | "export_failed" | "timeout") => void;
}
/**
 * Metrics exposed by the resilient exporter.
 */
export interface ResilientExporterMetrics {
    /** Total spans dropped due to backpressure or failure */
    dropped: number;
    /** Current queue size */
    queued: number;
    /** Total export failures */
    failures: number;
}
/**
 * Resilient exporter wrapper that:
 * - Drops spans when queue is full (never blocks)
 * - Catches export failures and emits metrics
 * - Times out stalled exports
 *
 * CRITICAL: Telemetry export must be fire-and-forget from the application's perspective.
 * Export failures should be observable via metrics, not via blocking or exceptions.
 */
export declare class ResilientExporter implements SpanExporter {
    private readonly delegate;
    private readonly maxQueueSize;
    private readonly exportTimeoutMs;
    private readonly onDrop;
    private queuedCount;
    private droppedCount;
    private exportFailures;
    private shuttingDown;
    constructor(config: ResilientExporterConfig);
    /**
     * Export spans with resilient error handling.
     *
     * IMPORTANT: Always returns SUCCESS to caller - export failures are
     * observable via metrics, not via the result callback.
     */
    export(spans: ReadableSpan[], resultCallback: (result: ExportResult) => void): void;
    /**
     * Shutdown the underlying exporter.
     * Marks exporter as shutting down to reject new exports.
     */
    shutdown(): Promise<void>;
    /**
     * Force flush the underlying exporter.
     */
    forceFlush(): Promise<void>;
    /**
     * Get current metrics for observability.
     */
    getMetrics(): ResilientExporterMetrics;
    /**
     * Reset metrics (for testing).
     */
    resetMetrics(): void;
}
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