axios-retryer/dist/plugins/CircuitBreakerPlugin.d.ts

TypeScript-first Axios retry library with concurrency limits, request priority, token refresh, response caching, and circuit breaker plugins.

import { AxiosRequestConfig, AxiosError, AxiosInstance, AxiosResponse } from 'axios';

declare const AXIOS_RETRYER_REQUEST_PRIORITIES: {
    readonly CRITICAL: 4;
    readonly HIGHEST: 3;
    readonly HIGH: 2;
    readonly MEDIUM: 1;
    readonly LOW: 0;
};
type AxiosRetryerRequestPriority = (typeof AXIOS_RETRYER_REQUEST_PRIORITIES)[keyof typeof AXIOS_RETRYER_REQUEST_PRIORITIES];

type RetryEventArgs<TEvents extends object, K extends keyof TEvents> = NonNullable<TEvents[K]> extends (...args: infer TArgs) => unknown ? TArgs : never;
type RetryEventListener<TEvents extends object, K extends keyof TEvents> = (...args: RetryEventArgs<TEvents, K>) => void;
/**
 * Terminal request error payload emitted by `onRequestError`.
 */
interface AxiosRetryerRequestErrorEvent {
    /** Final Axios error object that caused request failure. */
    error: AxiosError;
    /** Final Axios request config that failed. */
    config: AxiosRequestConfig;
    /** HTTP status if available, otherwise `null` for network-level failures. */
    status: number | null;
    /** Request identifier if available. */
    requestId?: string;
    /** Total attempts performed including the initial attempt. */
    attempts: number;
    /** Whether the final error shape is considered retryable by the active strategy. */
    retryable: boolean;
}
/**
 * Queue-entry payload emitted by `onRequestQueued`.
 */
interface AxiosRetryerRequestQueuedEvent {
    /** Request identifier generated or assigned by RetryManager. */
    requestId: string;
    /** Request config entering the queue. */
    config: AxiosRequestConfig;
    /** Resolved priority used for queue ordering. */
    priority: AxiosRetryerRequestPriority;
    /** Queue size immediately after this request was enqueued. */
    queueSize: number;
}
/**
 * Queue-dispatch payload emitted by `onRequestDispatched`.
 */
interface AxiosRetryerRequestDispatchedEvent {
    /** Request identifier generated or assigned by RetryManager. */
    requestId: string;
    /** Request config dispatched from the queue. */
    config: AxiosRequestConfig;
    /** Resolved priority used for queue ordering. */
    priority: AxiosRetryerRequestPriority;
    /** Time spent waiting in the queue before dispatch (milliseconds). */
    queuedForMs: number;
}
/**
 * Success payload emitted by `onRequestSucceeded`.
 */
interface AxiosRetryerRequestSucceededEvent {
    /** Request identifier generated or assigned by RetryManager. */
    requestId?: string;
    /** Final request config that succeeded. */
    config: AxiosRequestConfig;
    /** Final HTTP status code. */
    status: number;
    /** Total attempts performed including the initial attempt. */
    attempts: number;
}
/**
 * Core events exposed by RetryManager without any plugins attached.
 */
interface CoreRetryEvents {
    /**
     * Triggered when the retry process begins.
     */
    onRetryProcessStarted?: () => void;
    /**
     * Triggered before each retry attempt.
     * @param config The Axios request configuration being retried.
     */
    beforeRetry?: (config: AxiosRequestConfig) => void;
    /**
     * Triggered after a retry attempt.
     * @param config The Axios request configuration being retried.
     * @param success Whether the retry was successful.
     * @param error If the retry failed, the error that caused the failure.
     */
    afterRetry?: (config: AxiosRequestConfig, success: boolean, error?: AxiosError) => void;
    /**
     * Triggered when a retry is scheduled and waiting for the specified delay.
     * @param delayMs The delay in milliseconds.
     * @param config The Axios request configuration.
     */
    onRetryScheduled?: (delayMs: number, config: AxiosRequestConfig) => void;
    /**
     * Triggered for each failed retry attempt.
     * @param config The failed Axios request configuration.
     */
    onFailure?: (config: AxiosRequestConfig) => void;
    /**
     * Triggered when a request enters the queue.
     *
     * @param payload Queue entry metadata for this request.
     */
    onRequestQueued?: (payload: AxiosRetryerRequestQueuedEvent) => void;
    /**
     * Triggered when a queued request is dispatched from the queue to the network layer.
     *
     * @param payload Dispatch metadata including queue wait duration.
     */
    onRequestDispatched?: (payload: AxiosRetryerRequestDispatchedEvent) => void;
    /**
     * Triggered when a request succeeds (initial attempt or after retries).
     *
     * @param payload Success metadata for this request.
     */
    onRequestSucceeded?: (payload: AxiosRetryerRequestSucceededEvent) => void;
    /**
     * Triggered once when a request fails terminally (all retries exhausted or no-retry terminal path).
     * Unlike `onFailure`, this event is emitted only for the final failure.
     *
     * @param payload Terminal error context for application-level handling.
     */
    onRequestError?: (payload: AxiosRetryerRequestErrorEvent) => void;
    /**
     * Triggered when all retries are completed.
     */
    onRetryProcessFinished?: () => void;
    /**
     * Triggered when an in-flight retry delay timer is cancelled — either because
     * the user aborted the request (`source: 'user'`) or because the system shut
     * the request down (`source: 'system'`, e.g. plugin destroy, queue clear).
     */
    onRetryTimerCancelled?: (payload: {
        requestId: string;
        source: 'user' | 'system';
    }) => void;
    /**
     * Triggered when a request cancelled.
     * @param requestId Id of the cancelled request.
     */
    onRequestCancelled?: (requestId: string) => void;
    /**
     * Called when a request fails due to network or connection issues, meaning
     * no valid server response was received (e.g., user is offline).
     *
     * @param request - The Axios request config that encountered a connection error.
     */
    onInternetConnectionError?: (request: AxiosRequestConfig) => void;
    /**
     * Triggered when a blocking request (at or above `blockingPriorityThreshold`) fails terminally.
     * Only fires when `blockingPriorityThreshold` is configured.
     *
     * @param config The Axios request config of the failed blocking request.
     */
    onBlockingRequestFailed?: (config: AxiosRequestConfig) => void;
    /**
     * Triggered when every in-flight blocking request (at or above `blockingPriorityThreshold`)
     * has **succeeded** (terminal success) and none remain in the internal blocker set.
     * Not emitted when a blocker fails (`onBlockingRequestFailed`) or is cancelled.
     * Only fires when `blockingPriorityThreshold` is configured.
     */
    onAllBlockingRequestsResolved?: () => void;
}
type RetryManagerEvents<TPluginEvents extends object = Record<never, never>> = {
    [K in keyof CoreRetryEvents | keyof TPluginEvents]: K extends keyof TPluginEvents ? K extends keyof CoreRetryEvents ? CoreRetryEvents[K] & TPluginEvents[K] : TPluginEvents[K] : K extends keyof CoreRetryEvents ? CoreRetryEvents[K] : never;
};

/**
 * Represents the distribution of different error types encountered
 */
interface ErrorTypesDistribution {
    /** Number of network-related errors (e.g., connection failures) */
    network: number;
    /** Number of 5xx server errors */
    server5xx: number;
    /** Number of 4xx client errors */
    client4xx: number;
    /** Number of canceled requests */
    cancelled: number;
}
/**
 * Represents metrics for a specific request priority level
 */
interface PriorityMetrics {
    /** The priority level (higher numbers indicate higher priority) */
    priority: number;
    /** Total number of retry attempts for this priority */
    total: number;
    /** Number of successful retries for this priority */
    successes: number;
    /** Number of failed retries for this priority */
    failures: number;
    /** Success rate percentage for this priority (0-100) */
    successRate: number;
    /** Failure rate percentage for this priority (0-100) */
    failureRate: number;
}
/**
 * AxiosRetryer detailed metrics
 * */
interface AxiosRetryerDetailedMetrics {
    /** Total number of requests made through the retryer */
    totalRequests: number;
    /** Number of successfully completed retries */
    successfulRetries: number;
    /** Number of failed retry attempts */
    failedRetries: number;
    /** Requests that failed all retry attempts */
    completelyFailedRequests: number;
    /** Requests canceled before completion */
    canceledRequests: number;
    /** Critical priority requests that failed all retries */
    completelyFailedCriticalRequests: number;
    /** Distribution of error types encountered */
    errorTypesDistribution: ErrorTypesDistribution;
    /** Distribution of retry attempts across all requests */
    retryAttemptsDistribution: Record<number, number>;
    /** Count of requests by priority level */
    requestCountsByPriority: Record<number, number>;
    /** Average time spent in queue (seconds) */
    avgQueueWait: number;
    /** Average delay between retry attempts (seconds) */
    avgRetryDelay: number;
    /** Detailed metrics grouped by request priority */
    priorityMetrics: PriorityMetrics[];
    /** Timer health and accumulation metrics */
    timerHealth: {
        /** Number of active internal timers */
        activeTimers: number;
        /** Number of active retry timers */
        activeRetryTimers: number;
        /** Health score (0 = excellent, 100+ = potential issues) */
        healthScore: number;
    };
}
/**
 * Interface for pluggable metrics recording.
 * The core library ships with no-op metrics by default.
 * Use MetricsPlugin for full metrics collection.
 */
interface MetricsRecorder {
    reset(): void;
    buildDetailedMetrics(timerStats: {
        activeTimers: number;
        activeRetryTimers: number;
    }): AxiosRetryerDetailedMetrics;
    emitMetricsUpdated?(): void;
}

/**
 * Logger interface used by RetryManager and its collaborators.
 * Supply a custom implementation via {@link RetryManagerOptions.logger}
 * to redirect or suppress log output.
 */
interface Logger {
    log(message: string, data?: unknown): void;
    error(message: string, error?: unknown): void;
    warn(message: string, data?: unknown): void;
    debug(message: string, meta?: unknown): void;
}
/**
 * Context object passed to plugins during initialization and teardown.
 * Provides the plugin-facing view of RetryManager capabilities including
 * plugin-only wiring hooks that are not part of the public manager API.
 */
interface PluginContext<TPluginEvents extends object = Record<never, never>> {
    /** The Axios instance managed by RetryManager. */
    readonly axiosInstance: AxiosInstance;
    /** Returns the configured logger. */
    getLogger(): Logger;
    /** Subscribe to a manager or plugin event. */
    on<K extends keyof RetryManagerEvents<TPluginEvents>>(event: K, listener: RetryEventListener<RetryManagerEvents<TPluginEvents>, K>): void;
    /** Unsubscribe from a manager or plugin event. */
    off<K extends keyof RetryManagerEvents<TPluginEvents>>(event: K, listener: RetryEventListener<RetryManagerEvents<TPluginEvents>, K>): boolean;
    /** Fire all listeners registered for this event. */
    emit<K extends keyof RetryManagerEvents<TPluginEvents>>(event: K, ...args: RetryEventArgs<RetryManagerEvents<TPluginEvents>, K>): void;
    /**
     * Identical to `emit` — fires all listeners registered for this event.
     *
     * Kept for backward compatibility with existing plugins. There is no semantic
     * distinction from `emit`: prefer `emit` in new code.
     */
    triggerAndEmit<K extends keyof RetryManagerEvents<TPluginEvents>>(event: K, ...args: RetryEventArgs<RetryManagerEvents<TPluginEvents>, K>): void;
    /** Cancel a specific in-flight or queued request by its ID. */
    cancelRequest(requestId: string): void;
    /** Cancel all active and queued requests. */
    cancelAllRequests(): void;
    /** Cancel only requests currently waiting in the queue. */
    cancelQueuedRequests(): void;
    /**
     * Register a queue gate that must approve each request before it is dispatched.
     * Used by plugins that need to block request processing under certain conditions.
     */
    registerQueueGate(name: string, canProcess: (request: AxiosRequestConfig) => boolean): void;
    /** Remove a previously registered queue gate. */
    unregisterQueueGate(name: string): boolean;
    /** Trigger a queue drain pass. Useful after a gate condition changes. */
    refreshQueue(): void;
    /**
     * Register or unregister a metrics recorder.
     * Pass `null` to detach. Used by MetricsPlugin to expose metric data to the RetryManager's getMetrics() method.
     */
    registerMetricsRecorder(recorder: MetricsRecorder | null): void;
    /**
     * Return active timer counts.
     * Used by MetricsPlugin to populate the timerHealth section of detailed metrics.
     */
    getTimerStats(): {
        activeTimers: number;
        activeRetryTimers: number;
    };
    /**
     * Release lifecycle tracking for a request config and mark its queue slot complete.
     * Used by TokenRefreshPlugin when a tracked request is intercepted for token refresh.
     */
    releaseRequestTracking(config: AxiosRequestConfig): void;
}
/**
 * AxiosRetryer plugin interface that can be attached with {@link RetryManager.use} and removed with {@link RetryManager.unuse}
 * */
interface RetryPlugin<TPluginEvents extends object = Record<never, never>> {
    /**
     * Plugin name. Should be unique
     * */
    name: string;
    /**
     * Plugin version (e.g. 1.0.0)
     * */
    version: string;
    /**
     * Phantom covariant marker for TypeScript to infer `TPluginEvents` at call sites
     * such as `manager.use(plugin)`. Never set this at runtime; implementations may
     * simply omit it (it is always `undefined`).
     * */
    readonly _events?: Readonly<TPluginEvents>;
    /**
     * Called when the plugin is attached and initialized.
     * @param context Plugin context providing manager capabilities and plugin-only wiring hooks.
     * */
    initialize: (context: PluginContext<TPluginEvents>) => void;
    /**
     * Called before the plugin is removed.
     * @param context Plugin context providing manager capabilities and plugin-only wiring hooks.
     * */
    onBeforeDestroyed?: (context: PluginContext<TPluginEvents>) => void;
}

declare const CIRCUIT_BREAKER_STATES: {
    readonly CLOSED: "CLOSED";
    readonly OPEN: "OPEN";
    readonly HALF_OPEN: "HALF_OPEN";
};
type CircuitBreakerState = (typeof CIRCUIT_BREAKER_STATES)[keyof typeof CIRCUIT_BREAKER_STATES];
declare const CIRCUIT_BREAKER_SCOPES: {
    readonly HOST: "host";
    readonly URL: "url";
    readonly HOST_AND_URL: "host+url";
};
type CircuitBreakerScope = (typeof CIRCUIT_BREAKER_SCOPES)[keyof typeof CIRCUIT_BREAKER_SCOPES];
/**
 * Configuration options for the Circuit Breaker behavior.
 */
interface CircuitBreakerOptions {
    /**
     * Number of consecutive failures required to trip the circuit.
     * Once this threshold is exceeded, the circuit transitions from `CLOSED` to `OPEN`.
     */
    failureThreshold: number;
    /**
     * Duration (in milliseconds) the circuit remains in the `OPEN` state
     * before allowing a test request in the `HALF_OPEN` state.
     */
    openTimeout: number;
    /**
     * Maximum number of test requests allowed in `HALF_OPEN` state
     * before deciding to either reset (back to `CLOSED`) or trip again to `OPEN`.
     */
    halfOpenMax: number;
    /**
     * Number of successful test requests required in HALF_OPEN state to reset the circuit.
     * Must be <= halfOpenMax.
     */
    successThreshold?: number;
    /**
     * If true, uses a sliding window approach to count failures over time rather than consecutive failures.
     */
    useSlidingWindow?: boolean;
    /**
     * The duration (in milliseconds) of the sliding window when useSlidingWindow is true.
     */
    slidingWindowSize?: number;
    /**
     * Callback function to determine which errors should contribute to circuit breaking.
     * If not provided, all errors count.
     */
    shouldCountError?: (error: AxiosError) => boolean;
    /**
     * Adaptive timeout configuration. When true, the circuit breaker will track response times
     * and adjust timeouts accordingly.
     */
    adaptiveTimeout?: boolean;
    /**
     * Percentile (0-1) to use for adaptive timeout calculation. Default is 0.95 (95th percentile).
     */
    adaptiveTimeoutPercentile?: number;
    /**
     * Number of historical response times to track for adaptive timeout calculation.
     */
    adaptiveTimeoutSampleSize?: number;
    /**
     * Timeout multiplier (e.g., 1.5 = 150% of the calculated percentile).
     */
    adaptiveTimeoutMultiplier?: number;
    /**
     * Maximum number of unique scope keys tracked in the adaptive-timeout response-metrics map.
     * Prevents unbounded memory growth. When the cap is reached, the oldest entry is evicted.
     * Default: 500.
     */
    maxTrackedScopes?: number;
    /**
     * Allow specific endpoints to be excluded from circuit breaking.
     *
     * String patterns use exact URL equality. `RegExp` patterns are tested against
     * the full request URL on every request — prefer string patterns when possible.
     *
     * **Security note (ReDoS):** Avoid catastrophically backtracking patterns such as
     * `/(a+)+$/` combined with long non-matching URLs. JavaScript's regex engine is
     * single-threaded and synchronous; a pathological pattern will block the event loop.
     * Validate any user-controlled or externally-sourced patterns before use.
     */
    excludeUrls?: readonly (string | RegExp)[];
    /**
     * Controls how circuit state is grouped.
     * `host+url` scopes by host and normalized URL, which is the default.
     */
    scope?: CircuitBreakerScope | ((config: AxiosRequestConfig) => string);
    /**
     * Optional adapter for sharing circuit state across processes or hosts.
     */
    stateAdapter?: CircuitBreakerStateAdapter;
}
interface CircuitBreakerFailureRecord {
    timestamp: number;
    url: string;
    status?: number;
    errorCode?: string;
}
interface CircuitBreakerScopeState {
    state: CircuitBreakerState;
    failureCount: number;
    successCount: number;
    halfOpenCount: number;
    nextAttempt: number;
    recentFailures: CircuitBreakerFailureRecord[];
    lastFailureStatus?: number;
    lastFailureCode?: string;
}
interface CircuitBreakerScopeMetrics {
    scopeKey: string;
    url: string;
    host?: string;
    state: CircuitBreakerState;
    failureCount: number;
    halfOpenCount: number;
    successCount: number;
    nextAttemptIn: number;
    failuresInWindow: number;
}
interface CircuitBreakerAdaptiveTimeoutMetrics {
    scopeKey: string;
    url: string;
    host?: string;
    timeoutMs: number;
    p95ResponseTimeMs: number;
    samplesCount: number;
}
interface CircuitBreakerMetrics {
    state: CircuitBreakerState;
    failureCount: number;
    halfOpenCount: number;
    successCount: number;
    nextAttemptIn: number;
    failuresInWindow: number;
    adaptiveTimeouts: CircuitBreakerAdaptiveTimeoutMetrics[];
    scopeMetrics: CircuitBreakerScopeMetrics[];
}
interface CircuitBreakerStateAdapter {
    get(key: string): CircuitBreakerScopeState | undefined | Promise<CircuitBreakerScopeState | undefined>;
    set(key: string, state: CircuitBreakerScopeState): void | Promise<void>;
    delete(key: string): void | Promise<void>;
    clear(): void | Promise<void>;
}
interface CircuitBreakerPluginEvents {
    onCircuitStateChanged?: (payload: {
        scopeKey: string;
        from: CircuitBreakerState;
        to: CircuitBreakerState;
        reason: 'failure-threshold' | 'half-open-failure' | 'open-timeout-elapsed' | 'success-threshold-reached' | 'manual-reset';
        nextAttemptIn?: number;
    }) => void;
}

interface ResponseTimeMetrics {
    times: number[];
    sampleSize: number;
    lastCalculated: number;
    currentPercentileMs: number;
    scopeKey: string;
    normalizedUrl: string;
    host?: string;
}

/**
 * Default in-memory state adapter. Stores circuit state as deep clones to
 * prevent accidental mutation of internal state from external references.
 */
declare class InMemoryCircuitBreakerStateAdapter implements CircuitBreakerStateAdapter {
    private readonly state;
    get(key: string): CircuitBreakerScopeState | undefined;
    set(key: string, state: CircuitBreakerScopeState): void;
    delete(key: string): void;
    clear(): void;
}

/**
 * Enhanced CircuitBreakerPlugin with sliding window failure counting,
 * selective error monitoring, adaptive timeout management, granular recovery,
 * URL exclusion, scoped circuit state, and optional distributed state adapters.
 *
 * @implements {RetryPlugin}
 */
declare class CircuitBreakerPlugin implements RetryPlugin<CircuitBreakerPluginEvents> {
    static STATES: {
        readonly CLOSED: "CLOSED";
        readonly OPEN: "OPEN";
        readonly HALF_OPEN: "HALF_OPEN";
    };
    readonly name = "CircuitBreakerPlugin";
    readonly version = "2.0.0";
    readonly _events?: Readonly<CircuitBreakerPluginEvents>;
    private readonly _options;
    private _requestInterceptorId?;
    private _responseInterceptorId?;
    private _context;
    private readonly _adaptiveTimeoutTracker;
    private readonly _scopeManager;
    private readonly _failureWindow;
    private readonly _metricBaselines;
    constructor(options?: Partial<CircuitBreakerOptions>);
    /** @internal */
    get _responseMetrics(): Record<string, ResponseTimeMetrics>;
    /** @internal */
    get _scopeStateCache(): Map<string, CircuitBreakerScopeState>;
    /** @internal */
    get _knownScopes(): Map<string, {
        scopeKey: string;
        normalizedUrl: string;
        host?: string;
    }>;
    /** @internal */
    _normalizeUrl(url: string): string;
    /** @internal */
    _resolveScopeKey(config: AxiosRequestConfig, normalizedUrl: string, host?: string): string;
    /** @internal */
    _getScopeDetails(config: AxiosRequestConfig): {
        scopeKey: string;
        normalizedUrl: string;
        host?: string;
    };
    /** @internal */
    _writeScopeState(scopeKey: string, state: CircuitBreakerScopeState): Promise<void>;
    initialize(context: PluginContext<CircuitBreakerPluginEvents>): void;
    onBeforeDestroyed(context: PluginContext<CircuitBreakerPluginEvents>): void;
    getState(scopeKey?: string): CircuitBreakerState;
    manualReset(scopeKey?: string): void;
    /**
     * Backwards-compatible alias retained for existing tests and internal callers.
     * @internal
     */
    _reset(scopeKey?: string): void;
    /**
     * @internal Exposed for test inspection only; not part of the public API.
     */
    _trackResponseTime(response: AxiosResponse): void;
    resetMetrics(): void;
    getAdaptiveTimeoutMetrics(): CircuitBreakerMetrics['adaptiveTimeouts'];
    getMetrics(): CircuitBreakerMetrics;
    private _tripScope;
    private _resetScope;
    private _transitionToHalfOpen;
    private _emitStateChange;
    private _shouldCountError;
    private _isUrlExcluded;
    private _createCircuitStateError;
    private _getScopeMetrics;
    private _getVisibleCounter;
    private _getVisibleFailuresInWindow;
}

declare class CircuitBreakerStateError extends AxiosError {
    readonly circuitState: CircuitBreakerState;
    constructor(message: string, circuitState: CircuitBreakerState, request: AxiosRequestConfig, code?: string, response?: AxiosResponse);
}

/**
 * Creates a CircuitBreakerPlugin instance.
 * Functional alternative to using the `new CircuitBreakerPlugin()` constructor.
 *
 * The circuit breaker pattern prevents repeated requests to a failing service by
 * temporarily blocking requests after a threshold of failures is reached.
 *
 * @param options Configuration options for the CircuitBreakerPlugin
 * @returns A configured CircuitBreakerPlugin instance
 *
 * @example
 * ```typescript
 * const circuitBreaker = createCircuitBreaker({
 *   failureThreshold: 5,     // Trip circuit after 5 consecutive failures
 *   openTimeout: 30000,      // Remain open for 30s before allowing half-open test
 *   halfOpenMax: 1,          // Allow 1 test request in half-open state
 *   useSlidingWindow: true,  // Use sliding window for failure analysis
 *   slidingWindowSize: 60000 // 60-second sliding window
 * });
 *
 * manager.use(circuitBreaker);
 * ```
 */
declare function createCircuitBreaker(options?: Partial<CircuitBreakerOptions>): CircuitBreakerPlugin;

export { CIRCUIT_BREAKER_SCOPES, CIRCUIT_BREAKER_STATES, CircuitBreakerPlugin, CircuitBreakerStateError, InMemoryCircuitBreakerStateAdapter, createCircuitBreaker };
export type { CircuitBreakerAdaptiveTimeoutMetrics, CircuitBreakerFailureRecord, CircuitBreakerMetrics, CircuitBreakerOptions, CircuitBreakerPluginEvents, CircuitBreakerScope, CircuitBreakerScopeMetrics, CircuitBreakerScopeState, CircuitBreakerState, CircuitBreakerStateAdapter };