Merge branch 'exponential-backoff' into sse-branc
This commit is contained in:
22
source/errors.ts
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22
source/errors.ts
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@@ -0,0 +1,22 @@
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/**
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* Error thrown when the maximum number of retries is hit in an exponential backoff
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*/
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export class ExponentialBackoffMaxRetriesHitError extends Error {
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constructor(errors: Array<Error>) {
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super('Exponential backoff: Max retries hit', { cause: errors });
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this.name = 'ExponentialBackoffMaxRetriesHitError';
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}
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}
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/**
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* Error thrown when the exponential backoff retries are stopped
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*/
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export class ExponentialBackoffStoppedRetriesError extends Error {
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constructor(reason: unknown) {
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// Convert the reason to an error if it is not an error
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const reasonError = reason instanceof Error ? reason : new Error(`${reason}`);
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super(`Exponential backoff was aborted: "${reasonError.message}"`, { cause: reasonError });
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this.name = 'ExponentialBackoffStoppedRetriesError';
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}
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}
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275
source/exponential-backoff.ts
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275
source/exponential-backoff.ts
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@@ -0,0 +1,275 @@
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import { ExponentialBackoffStoppedRetriesError, ExponentialBackoffMaxRetriesHitError } from './errors.ts';
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/**
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* Exponential backoff is a technique used to retry a function after a delay.
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*
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* The delay increases exponentially with each attempt, up to a maximum delay.
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*
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* The jitter is a random amount of time subtracted from the delay to prevent thundering herd problems.
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*
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* The growth rate is the factor by which the delay increases with each attempt.
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*/
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export class ExponentialBackoff {
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readonly #options: ExponentialBackoffOptions;
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/**
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* Creates a new exponential-backoff instance.
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*
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* Unspecified options use the defaults listed below.
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*
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* @param options - Exponential-backoff configuration overrides.
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* @param options.maxDelay - Maximum delay between retries. Default: `10_000` ms.
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* @param options.maxAttempts - Maximum number of attempts; `0` retries indefinitely. Default: `10`.
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* @param options.baseDelay - Delay used as the basis for the first retry. Default: `1_000` ms.
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* @param options.growthRate - Multiplier applied to the delay after each attempt. Default: `2`.
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* @param options.jitter - Maximum proportional reduction subtracted from each delay (0–1). Default: `0.1`.
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*/
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constructor(options: Partial<ExponentialBackoffOptions> = {}) {
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this.#options = {
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maxDelay: 10_000,
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maxAttempts: 10,
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baseDelay: 1_000,
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growthRate: 2,
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jitter: 0.1,
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...options,
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};
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ExponentialBackoff.validateOptions(this.#options);
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}
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/**
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* Create a new ExponentialBackoff instance
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*
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* @param config - The configuration for the exponential backoff
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* @returns The ExponentialBackoff instance
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*/
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static from(config?: Partial<ExponentialBackoffOptions>): ExponentialBackoff {
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const backoff = new ExponentialBackoff(config);
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return backoff;
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}
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/**
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* Run the function with exponential backoff
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*
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* @param taskFn - The function to run
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* @param onError - The callback to call when an error occurs
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* @param options - The configuration for the exponential backoff
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*
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* @throws An {@link ExponentialBackoffMaxRetriesHitError} with all the errors that were thrown by the task function
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* @throws An {@link ExponentialBackoffStoppedRetriesError} if the abort signal is activated
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*
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* @returns The result of the function
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*/
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static run<T>(
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taskFn: (callbackParameters: ExponentialBackoffCallbackParameters) => Promise<T>,
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onError = (_error: Error): void => {},
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options?: Partial<ExponentialBackoffOptions>,
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): Promise<T> {
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const backoff = ExponentialBackoff.from(options);
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return backoff.run(taskFn, onError);
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}
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/**
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* Calculate the delay before we should attempt to retry
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*
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* @param options - The configuration for the exponential backoff
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* @param attempt - The current attempt number
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* @returns The time in milliseconds before another attempt should be made
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*/
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public static calculateDelay(options: ExponentialBackoffOptions, attempt: number): number {
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// Get the power of the growth rate
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const power = options.growthRate ** attempt;
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// Get the delay before jitter or limit
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const rawDelay = options.baseDelay * power;
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// Cap the delay to the maximum. Do this before the jitter so jitter does not become larger than delay
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const cappedDelay = Math.min(rawDelay, options.maxDelay);
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// Get a random number for the amount to "jitter" the delay by
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const jitterAmount = Math.random();
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// Calculate the jitter
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const jitter = jitterAmount * options.jitter * cappedDelay;
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// Subtract the jitter from the delay
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return cappedDelay - jitter;
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}
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/**
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* Validate the options for the exponential backoff
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*
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* @param options - The options to validate
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*
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* @throws An error if the options are invalid
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*/
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public static validateOptions(options: ExponentialBackoffOptions): void {
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// Validate the max delay is a finite number not less than 0
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if (!Number.isFinite(options.maxDelay)) {
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throw new Error('maxDelay must be a finite number');
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}
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if (options.maxDelay < 0) {
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throw new Error('maxDelay must be not less than 0');
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}
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// Validate the max attempts is a finite number not less than 0
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if (!Number.isFinite(options.maxAttempts)) {
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throw new Error('maxAttempts must be a finite number');
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}
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if (options.maxAttempts < 0) {
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throw new Error('maxAttempts must be not less than 0');
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}
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// Validate the base delay is a finite number not less than 0
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if (!Number.isFinite(options.baseDelay)) {
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throw new Error('baseDelay must be a finite number');
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}
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if (options.baseDelay < 0) {
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throw new Error('baseDelay must be not less than 0');
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}
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// Validate the growth rate is a finite number not less than 0
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if (!Number.isFinite(options.growthRate)) {
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throw new Error('growthRate must be a finite number');
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}
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if (options.growthRate < 0) {
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throw new Error('growthRate must be not less than 0');
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}
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// Validate the jitter is a finite number not less than 0 or greater than 1
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if (!Number.isFinite(options.jitter)) {
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throw new Error('jitter must be a finite number');
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}
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if (options.jitter < 0 || options.jitter > 1) {
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throw new Error('jitter must be not less than 0 or greater than 1');
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}
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}
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/**
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* Run the function with exponential backoff
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*
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* If the function fails but we have not hit the max attempts, the error will be passed to the onError callback
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* and the function will be retried with an exponential delay
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*
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* If the function fails and we have hit the max attempts, an ExponentialBackoffMaxRetriesHitError will be thrown with all the errors that were thrown by the task function
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*
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* @param taskFn - The function to run
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* @param onError - The callback to call when an error occurs
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*
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* @throws An {@link ExponentialBackoffMaxRetriesHitError} with all the errors that were thrown by the task function
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* @throws An {@link ExponentialBackoffStoppedRetriesError} if the abort signal is activated
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*
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* @returns The result of the function
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*/
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async run<T>(
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taskFn: (callbackParameters: ExponentialBackoffCallbackParameters) => Promise<T>,
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onError = (_error: Error): void => {},
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): Promise<T> {
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// Initialize an abort signal to allow the task function to be aborted
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const abortController = new AbortController();
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const stopRetries = abortController.abort.bind(abortController);
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// Initialize an empty array to store the errors
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const errors: Error[] = [];
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// Initialize the attempt counter
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let attempt = 0;
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// If the max attempts is 0, we should continue indefinitely.
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const unlimitedAttempts = this.#options.maxAttempts === 0;
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// Loop until we succeed, hit the max attempts, or the abort signal is activated
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while (true) {
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try {
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// Await the promise before returning so its execution context remains in the try-catch
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// If we didn't await, this `run` function would successfully return and any errors would not be caught here.
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return await taskFn({ stopRetries });
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} catch (error) {
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// Store the error in case we fail every attempt
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const errorInstance = error instanceof Error ? error : new Error(`${error}`);
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onError(errorInstance);
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// If we have unlimited attempts, don't append this to the errors array to prevent a memory leak.
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if (!unlimitedAttempts) {
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errors.push(errorInstance);
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}
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}
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// Calculate the count for next attempt. Do this now so we can exit before waiting and before running the next attempt.
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const nextAttemptCount = attempt + 1;
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const nextAttemptExceedsMaxAttempts = nextAttemptCount >= this.#options.maxAttempts;
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// If the next attempt exceeds the max attempts, break out of the loop
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if (!unlimitedAttempts && nextAttemptExceedsMaxAttempts) {
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break;
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}
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// Check if the abort signal has been aborted
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if (abortController.signal.aborted) {
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// Throw an error if the abort signal has been aborted
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throw new ExponentialBackoffStoppedRetriesError(abortController.signal.reason);
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}
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// Wait before going to the next attempt
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const delay = ExponentialBackoff.calculateDelay(this.#options, attempt);
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await new Promise((resolve) => setTimeout(resolve, delay));
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attempt++;
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}
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// We completed the loop without ever succeeding. Throw an ExponentialBackoffMaxRetriesHitError with all the errors we got
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throw new ExponentialBackoffMaxRetriesHitError(errors);
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}
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}
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export type ExponentialBackoffOptions = {
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/**
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* The maximum delay between attempts in milliseconds
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*/
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maxDelay: number;
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/**
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* The maximum number of attempts. Passing 0 will result in infinite attempts.
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*/
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maxAttempts: number;
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/**
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* The base delay between attempts in milliseconds
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*/
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baseDelay: number;
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/**
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* The growth rate of the delay
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*/
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growthRate: number;
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/**
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* The jitter of the delay as a percentage of growthRate. The jitter is subtracted from the delay.
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*/
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jitter: number;
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};
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/**
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* The function to call to stop the retries.
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* This mimics the AbortSignal.abort function by taking in a reason for stopping
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*
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* @param reason - The reason for stopping the retries.
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*/
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export type ExponentialBackoffStopRetriesFunction = (reason: unknown) => void;
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/**
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* The parameters for the task function
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*
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* @param stopRetries - The function to call to stop the retries
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*/
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export type ExponentialBackoffCallbackParameters = {
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stopRetries: ExponentialBackoffStopRetriesFunction;
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};
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@@ -1,3 +1,4 @@
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export * from './exponential-backoff.ts';
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export * from './extended-json.ts';
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export * from './script.ts';
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export * from './sse-session/index.ts';
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595
test/exponential-backoff.test.ts
Normal file
595
test/exponential-backoff.test.ts
Normal file
@@ -0,0 +1,595 @@
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import { expect, test, vi } from 'vitest';
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import { ExponentialBackoff } from '../source/exponential-backoff.ts';
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import { ExponentialBackoffMaxRetriesHitError, ExponentialBackoffStoppedRetriesError } from '../source/errors.ts';
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/**
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* A valid options object that satisfies {@link ExponentialBackoff.validateOptions}.
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*/
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const validExponentialBackoffOptions = {
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maxDelay: 10_000,
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maxAttempts: 10,
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baseDelay: 1_000,
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growthRate: 2,
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jitter: 0.1,
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};
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/**
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* Tests that the static {@link ExponentialBackoff.run} helper creates a throwaway instance
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* with library defaults (including the default 1000ms base delay) when no options are passed.
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*/
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const testExponentialBackoffRunUsesDefaultOptions = async (): Promise<void> => {
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// Fake timers let us advance time without waiting real seconds between retries.
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vi.useFakeTimers();
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// Pin Math.random to 0 so jitter does not reduce the default delay.
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vi.spyOn(Math, 'random').mockReturnValue(0);
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try {
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// The wrapped function fails on its first invocation and succeeds on the second.
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// That forces ExponentialBackoff.run down the retry path using default options.
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const rejectThenResolveFn = vi.fn().mockRejectedValueOnce(new Error('retry me'))
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.mockResolvedValueOnce('static-result');
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// Call the static helper with no onError and no options — defaults apply entirely.
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const promise = ExponentialBackoff.run(rejectThenResolveFn);
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// Yield one microtask so the first (immediate) attempt completes and schedules the retry timer.
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await Promise.resolve();
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expect(rejectThenResolveFn).toHaveBeenCalledTimes(1);
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// Default baseDelay is 1000ms; advancing less would not trigger the retry yet.
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await vi.advanceTimersByTimeAsync(1_000);
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// The retry should have succeeded and returned the resolved value from the mock.
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await expect(promise).resolves.toBe('static-result');
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expect(rejectThenResolveFn).toHaveBeenCalledTimes(2);
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} finally {
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vi.useRealTimers();
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vi.restoreAllMocks();
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}
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};
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/**
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* Tests that {@link ExponentialBackoff.run} accepts a partial options object and merges it
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* with defaults, still retrying when only some fields are overridden.
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*/
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const testExponentialBackoffRunWithPartialOptions = async (): Promise<void> => {
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// Same fail-then-succeed pattern; we only care that partial options still enable a retry.
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const rejectThenResolveFn = vi.fn().mockRejectedValueOnce(new Error('retry me'))
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.mockResolvedValueOnce('done');
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// baseDelay/jitter of 0 skip real waiting; maxAttempts: 3 gives headroom for one retry.
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// onError is explicitly undefined to verify the default no-op handler is used.
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const result = await ExponentialBackoff.run(rejectThenResolveFn, undefined, {
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baseDelay: 0,
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jitter: 0,
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maxAttempts: 3,
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});
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expect(result).toBe('done');
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expect(rejectThenResolveFn).toHaveBeenCalledTimes(2);
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};
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/**
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* Tests that calling {@link ExponentialBackoff.run} on a constructed instance applies
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* the instance's stored options when no per-run options are supplied.
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*/
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const testExponentialBackoffInstanceRunUsesDefaultOnError = async (): Promise<void> => {
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const rejectThenResolveFn = vi.fn().mockRejectedValueOnce(new Error('retry me'))
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.mockResolvedValueOnce('instance-result');
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// Options live on the instance; run(fn) should read them instead of static defaults.
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const backoff = new ExponentialBackoff({ baseDelay: 0, jitter: 0, maxAttempts: 3 });
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const result = await backoff.run(rejectThenResolveFn);
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expect(result).toBe('instance-result');
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expect(rejectThenResolveFn).toHaveBeenCalledTimes(2);
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||||
};
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||||
|
||||
/**
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* Tests the happy path: the wrapped function succeeds immediately and no retry machinery runs.
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||||
*/
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||||
const testExponentialBackoffSucceedsOnFirstAttempt = async (): Promise<void> => {
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// Always resolves — never enters the catch/retry branch.
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const resolveFn = vi.fn(async () => 'success');
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const onError = vi.fn();
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||||
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||||
const result = await ExponentialBackoff.run(resolveFn, onError, {
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||||
baseDelay: 0,
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||||
jitter: 0,
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||||
});
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||||
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||||
expect(result).toBe('success');
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||||
expect(resolveFn).toHaveBeenCalledOnce();
|
||||
expect(onError).not.toHaveBeenCalled();
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that retries continue across multiple failures until the function eventually resolves.
|
||||
*/
|
||||
const testExponentialBackoffRetriesUntilSuccess = async (): Promise<void> => {
|
||||
// Three invocations: two rejections then a success on the third call.
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||||
const tripleRejectFn = vi
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||||
.fn()
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||||
.mockRejectedValueOnce(new Error('attempt 1'))
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||||
.mockRejectedValueOnce(new Error('attempt 2'))
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||||
.mockResolvedValueOnce('success');
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||||
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||||
// maxAttempts: 5 is high enough that we stop because fn succeeded, not because we hit the cap.
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||||
const result = await ExponentialBackoff.run(tripleRejectFn, () => {}, {
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||||
baseDelay: 0,
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||||
jitter: 0,
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||||
maxAttempts: 5,
|
||||
});
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||||
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||||
expect(result).toBe('success');
|
||||
expect(tripleRejectFn).toHaveBeenCalledTimes(3);
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that the onError callback is invoked once for every failed attempt, including the last one
|
||||
* before an ExponentialBackoffMaxRetriesHitError is thrown to the caller.
|
||||
*/
|
||||
const testExponentialBackoffCallsOnErrorForEachFailure = async (): Promise<void> => {
|
||||
const error = new Error('temporary failure');
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||||
|
||||
// Always rejects with the same error — we will exhaust all attempts.
|
||||
const rejectFn = vi.fn().mockRejectedValue(error);
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||||
const onError = vi.fn();
|
||||
|
||||
// maxAttempts: 3 means three tries total, all of which will fail.
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||||
await expect(ExponentialBackoff.run(rejectFn, onError, {
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||||
baseDelay: 0,
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||||
jitter: 0,
|
||||
maxAttempts: 3,
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||||
})).rejects.toThrow(ExponentialBackoffMaxRetriesHitError);
|
||||
|
||||
expect(onError).toHaveBeenCalledTimes(3);
|
||||
expect(onError).toHaveBeenCalledWith(error);
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that when all attempts are exhausted the caller receives an ExponentialBackoffMaxRetriesHitError
|
||||
* with every task error preserved in order on the cause.
|
||||
*/
|
||||
const testExponentialBackoffThrowsMaxRetriesHitErrorWhenExhausted = async (): Promise<void> => {
|
||||
const firstError = new Error('first');
|
||||
const lastError = new Error('last');
|
||||
|
||||
// Two distinct errors so we can prove both are collected, not just the last one.
|
||||
const doubleRejectFn = vi.fn().mockRejectedValueOnce(firstError)
|
||||
.mockRejectedValueOnce(lastError);
|
||||
|
||||
try {
|
||||
await ExponentialBackoff.run(doubleRejectFn, () => {}, {
|
||||
baseDelay: 0,
|
||||
jitter: 0,
|
||||
maxAttempts: 2,
|
||||
});
|
||||
expect.fail('Expected ExponentialBackoffMaxRetriesHitError to be thrown');
|
||||
} catch (error) {
|
||||
expect(error).toBeInstanceOf(ExponentialBackoffMaxRetriesHitError);
|
||||
expect((error as ExponentialBackoffMaxRetriesHitError).cause).toEqual([ firstError, lastError ]);
|
||||
}
|
||||
|
||||
expect(doubleRejectFn).toHaveBeenCalledTimes(2);
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that rejections which are not Error instances are coerced to Error before onError runs,
|
||||
* so callers always observe a consistent error type in the callback.
|
||||
*/
|
||||
const testExponentialBackoffWrapsNonErrorThrows = async (): Promise<void> => {
|
||||
// Reject with a plain string — not an Error subclass.
|
||||
const rejectedFn = vi.fn().mockRejectedValue('not-an-error');
|
||||
const onError = vi.fn();
|
||||
|
||||
// Single attempt — we fail fast and inspect what onError received.
|
||||
try {
|
||||
await ExponentialBackoff.run(rejectedFn, onError, {
|
||||
baseDelay: 0,
|
||||
jitter: 0,
|
||||
maxAttempts: 1,
|
||||
});
|
||||
expect.fail('Expected ExponentialBackoffMaxRetriesHitError to be thrown');
|
||||
} catch (error) {
|
||||
expect(error).toBeInstanceOf(ExponentialBackoffMaxRetriesHitError);
|
||||
const [ wrappedError ] = (error as ExponentialBackoffMaxRetriesHitError).cause as Error[];
|
||||
expect(wrappedError).toBeInstanceOf(Error);
|
||||
expect(wrappedError.message).toBe('not-an-error');
|
||||
}
|
||||
|
||||
expect(onError).toHaveBeenCalledOnce();
|
||||
expect(onError.mock.calls[0][0]).toBeInstanceOf(Error);
|
||||
expect(onError.mock.calls[0][0].message).toBe('not-an-error');
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that when the task function succeeds and the abort signal is aborted, the result is returned
|
||||
* and the onError callback is not called.
|
||||
*/
|
||||
const testExponentialBackoffRunSuccessAndAbortSignal = async (): Promise<void> => {
|
||||
// Define the function which aborts the exponential backoff and succeeds
|
||||
const abortAndSucceedFn = vi.fn(({ stopRetries }) => {
|
||||
stopRetries(new Error('retry me'));
|
||||
|
||||
return Promise.resolve('success');
|
||||
});
|
||||
const onErrorFn = vi.fn();
|
||||
|
||||
// Run the exponential backoff with the function and the onError callback
|
||||
const result = await ExponentialBackoff.run(abortAndSucceedFn, onErrorFn, {
|
||||
baseDelay: 0,
|
||||
jitter: 0,
|
||||
});
|
||||
|
||||
// Expect the result to be the success message
|
||||
expect(result).toBe('success');
|
||||
expect(abortAndSucceedFn).toHaveBeenCalledOnce();
|
||||
|
||||
// Expect the onError callback to not have been called
|
||||
expect(onErrorFn).not.toHaveBeenCalled();
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that when the abort signal is aborted with an error, an ExponentialBackoffStoppedRetriesError is thrown
|
||||
* with the error as the message.
|
||||
*/
|
||||
const testExponentialBackoffRunWithAbortSignal = async (): Promise<void> => {
|
||||
// Define the function which aborts the exponential backoff and throws an error
|
||||
const abortAndThrowFn = vi.fn(({ stopRetries }) => {
|
||||
stopRetries(new Error('exponential backoff aborted'));
|
||||
throw new Error('error message');
|
||||
});
|
||||
const onErrorFn = vi.fn();
|
||||
|
||||
// Define the expected error
|
||||
const expectedError = new ExponentialBackoffStoppedRetriesError(new Error('exponential backoff aborted'));
|
||||
|
||||
// Run the exponential backoff with the function and the onError callback and expect the error to be thrown
|
||||
await expect(ExponentialBackoff.run(abortAndThrowFn, onErrorFn, {
|
||||
baseDelay: 0,
|
||||
jitter: 0,
|
||||
})).rejects.toThrow(expectedError);
|
||||
|
||||
// Expect the onError callback to have been called once with the error
|
||||
expect(onErrorFn).toHaveBeenCalledOnce();
|
||||
expect(onErrorFn.mock.calls[0][0]).toBeInstanceOf(Error);
|
||||
expect(onErrorFn.mock.calls[0][0].message).toBe('error message');
|
||||
|
||||
// Expect the function to have been called once and not to have resolved
|
||||
expect(abortAndThrowFn).toHaveBeenCalledOnce();
|
||||
expect(abortAndThrowFn).not.toHaveResolved();
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that when the abort signal is aborted with a string, an ExponentialBackoffStoppedRetriesError is thrown
|
||||
* with the string as the message.
|
||||
*/
|
||||
const testExponentialBackoffRunAbortedStringCreatesError = async (): Promise<void> => {
|
||||
// Define the function which aborts the exponential backoff and throws an error
|
||||
const abortAndThrowStringFn = vi.fn(({ stopRetries }) => {
|
||||
stopRetries('exponential backoff aborted');
|
||||
|
||||
// eslint-disable-next-line
|
||||
throw 'error message';
|
||||
});
|
||||
const onErrorFn = vi.fn();
|
||||
|
||||
// Define the expected error, Note that we "stopRetries" with just a string, not an error. They are treated equivalently.
|
||||
const expectedError = new ExponentialBackoffStoppedRetriesError(new Error('exponential backoff aborted'));
|
||||
|
||||
// Run the exponential backoff with the function and the onError callback and expect the error to be thrown
|
||||
await expect(ExponentialBackoff.run(abortAndThrowStringFn, onErrorFn, {
|
||||
baseDelay: 0,
|
||||
jitter: 0,
|
||||
})).rejects.toThrow(expectedError);
|
||||
|
||||
// Expect the onError callback to have been called once with the error
|
||||
expect(onErrorFn).toHaveBeenCalledOnce();
|
||||
expect(onErrorFn.mock.calls[0][0]).toBeInstanceOf(Error);
|
||||
expect(onErrorFn.mock.calls[0][0].message).toBe('error message');
|
||||
|
||||
// Expect the function to have been called once and not to have resolved
|
||||
expect(abortAndThrowStringFn).toHaveBeenCalledOnce();
|
||||
expect(abortAndThrowStringFn).not.toHaveResolved();
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests the {@link ExponentialBackoff.from} factory and subsequent instance {@link ExponentialBackoff.run}
|
||||
* as an alternative to the static helper.
|
||||
*/
|
||||
const testExponentialBackoffFromAndInstanceRun = async (): Promise<void> => {
|
||||
const successfullyResolve = vi.fn(async () => 42);
|
||||
|
||||
// from() is a convenience constructor; run() on the result should behave like the static path.
|
||||
const backoff = ExponentialBackoff.from({
|
||||
baseDelay: 0,
|
||||
jitter: 0,
|
||||
});
|
||||
|
||||
const result = await backoff.run(successfullyResolve);
|
||||
|
||||
expect(result).toBe(42);
|
||||
expect(successfullyResolve).toHaveBeenCalledOnce();
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that maxAttempts: 0 disables the attempt cap so retries continue until the function succeeds.
|
||||
*/
|
||||
const testExponentialBackoffRetriesIndefinitelyWhenMaxAttemptsIsZero = async (): Promise<void> => {
|
||||
// Four invocations: three failures then success — would exceed a cap of 3 if one existed.
|
||||
const tripleRejectThenResolveFn = vi
|
||||
.fn()
|
||||
.mockRejectedValueOnce(new Error('attempt 1'))
|
||||
.mockRejectedValueOnce(new Error('attempt 2'))
|
||||
.mockRejectedValueOnce(new Error('attempt 3'))
|
||||
.mockResolvedValueOnce('eventually');
|
||||
|
||||
const result = await ExponentialBackoff.run(tripleRejectThenResolveFn, () => {}, {
|
||||
baseDelay: 0,
|
||||
jitter: 0,
|
||||
maxAttempts: 0,
|
||||
});
|
||||
|
||||
expect(result).toBe('eventually');
|
||||
expect(tripleRejectThenResolveFn).toHaveBeenCalledTimes(4);
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests the delay formula: each retry waits baseDelay * growthRate^attemptIndex milliseconds
|
||||
* (with jitter disabled so the math is exact).
|
||||
*/
|
||||
const testExponentialBackoffIncreasesDelayExponentially = async (): Promise<void> => {
|
||||
vi.useFakeTimers();
|
||||
vi.spyOn(Math, 'random').mockReturnValue(0.5);
|
||||
|
||||
try {
|
||||
const doubleRejectThenResolveFn = vi
|
||||
.fn()
|
||||
.mockRejectedValueOnce(new Error('attempt 1'))
|
||||
.mockRejectedValueOnce(new Error('attempt 2'))
|
||||
.mockResolvedValueOnce('success');
|
||||
|
||||
const promise = ExponentialBackoff.run(doubleRejectThenResolveFn, () => {}, {
|
||||
baseDelay: 100,
|
||||
growthRate: 2,
|
||||
jitter: 0,
|
||||
maxDelay: 10_000,
|
||||
maxAttempts: 5,
|
||||
});
|
||||
|
||||
// Attempt 0 fires synchronously on the first microtask tick.
|
||||
await Promise.resolve();
|
||||
expect(doubleRejectThenResolveFn).toHaveBeenCalledTimes(1);
|
||||
|
||||
// After attempt 0 fails, delay = 100 * 2^0 = 100ms before attempt 1.
|
||||
await vi.advanceTimersByTimeAsync(100);
|
||||
expect(doubleRejectThenResolveFn).toHaveBeenCalledTimes(2);
|
||||
|
||||
// After attempt 1 fails, delay = 100 * 2^1 = 200ms before attempt 2.
|
||||
await vi.advanceTimersByTimeAsync(200);
|
||||
expect(doubleRejectThenResolveFn).toHaveBeenCalledTimes(3);
|
||||
|
||||
await expect(promise).resolves.toBe('success');
|
||||
} finally {
|
||||
vi.useRealTimers();
|
||||
vi.restoreAllMocks();
|
||||
}
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that computed delay never exceeds maxDelay even when exponential growth would go higher.
|
||||
*/
|
||||
const testExponentialBackoffCapsDelayAtMaxDelay = async (): Promise<void> => {
|
||||
vi.useFakeTimers();
|
||||
vi.spyOn(Math, 'random').mockReturnValue(0.5);
|
||||
|
||||
try {
|
||||
const doubleRejectThenResolveFn = vi
|
||||
.fn()
|
||||
.mockRejectedValueOnce(new Error('attempt 1'))
|
||||
.mockRejectedValueOnce(new Error('attempt 2'))
|
||||
.mockResolvedValueOnce('success');
|
||||
|
||||
const promise = ExponentialBackoff.run(doubleRejectThenResolveFn, () => {}, {
|
||||
baseDelay: 1_000,
|
||||
growthRate: 4,
|
||||
jitter: 0,
|
||||
maxDelay: 2_000,
|
||||
maxAttempts: 5,
|
||||
});
|
||||
|
||||
await Promise.resolve();
|
||||
expect(doubleRejectThenResolveFn).toHaveBeenCalledTimes(1);
|
||||
|
||||
// attempt 0: 1000 * 4^0 = 1000ms, below the 2000ms cap.
|
||||
await vi.advanceTimersByTimeAsync(1_000);
|
||||
expect(doubleRejectThenResolveFn).toHaveBeenCalledTimes(2);
|
||||
|
||||
// attempt 1: uncapped would be 4000ms but maxDelay clamps to 2000ms.
|
||||
await vi.advanceTimersByTimeAsync(2_000);
|
||||
expect(doubleRejectThenResolveFn).toHaveBeenCalledTimes(3);
|
||||
|
||||
await expect(promise).resolves.toBe('success');
|
||||
} finally {
|
||||
vi.useRealTimers();
|
||||
vi.restoreAllMocks();
|
||||
}
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that jitter subtracts up to jitter * cappedDelay from the capped delay based on Math.random.
|
||||
*/
|
||||
const testExponentialBackoffAppliesJitter = async (): Promise<void> => {
|
||||
vi.useFakeTimers();
|
||||
// random = 1 → full 10% reduction: 1000 - (1 * 0.1 * 1000) = 900ms.
|
||||
vi.spyOn(Math, 'random').mockReturnValue(1);
|
||||
|
||||
try {
|
||||
const rejectThenResolveFn = vi.fn().mockRejectedValueOnce(new Error('attempt 1'))
|
||||
.mockResolvedValueOnce('success');
|
||||
|
||||
const promise = ExponentialBackoff.run(rejectThenResolveFn, () => {}, {
|
||||
baseDelay: 1_000,
|
||||
growthRate: 1,
|
||||
jitter: 0.1,
|
||||
maxDelay: 10_000,
|
||||
maxAttempts: 3,
|
||||
});
|
||||
|
||||
await Promise.resolve();
|
||||
expect(rejectThenResolveFn).toHaveBeenCalledTimes(1);
|
||||
|
||||
// Advancing 899ms is one ms short of the jittered delay; 900ms triggers the retry.
|
||||
await vi.advanceTimersByTimeAsync(899);
|
||||
expect(rejectThenResolveFn).toHaveBeenCalledTimes(1);
|
||||
|
||||
await vi.advanceTimersByTimeAsync(1);
|
||||
expect(rejectThenResolveFn).toHaveBeenCalledTimes(2);
|
||||
|
||||
await expect(promise).resolves.toBe('success');
|
||||
} finally {
|
||||
vi.useRealTimers();
|
||||
vi.restoreAllMocks();
|
||||
}
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that {@link ExponentialBackoff.validateOptions} accepts valid options, including boundary values of 0 and 1.
|
||||
*/
|
||||
const testExponentialBackoffValidateOptionsAcceptsValidOptions = (): void => {
|
||||
const validCases = [
|
||||
validExponentialBackoffOptions,
|
||||
{
|
||||
...validExponentialBackoffOptions,
|
||||
maxDelay: 0,
|
||||
maxAttempts: 0,
|
||||
baseDelay: 0,
|
||||
growthRate: 0,
|
||||
jitter: 0,
|
||||
},
|
||||
{
|
||||
...validExponentialBackoffOptions,
|
||||
jitter: 1,
|
||||
},
|
||||
] as const;
|
||||
|
||||
for (const options of validCases) {
|
||||
expect(() => ExponentialBackoff.validateOptions(options)).not.toThrow();
|
||||
}
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that {@link ExponentialBackoff.validateOptions} rejects negative numeric options.
|
||||
*/
|
||||
const testExponentialBackoffValidateOptionsRejectsNegativeValues = (): void => {
|
||||
// Define our test cases with each value being less than 0
|
||||
const negativeCases = [
|
||||
{ field: 'maxDelay', value: -1 },
|
||||
{ field: 'maxAttempts', value: -1 },
|
||||
{ field: 'baseDelay', value: -1 },
|
||||
{ field: 'growthRate', value: -1 },
|
||||
] as const;
|
||||
|
||||
// Iterate through the test cases and expect an error to be thrown
|
||||
for (const { field, value } of negativeCases) {
|
||||
expect(() =>
|
||||
ExponentialBackoff.validateOptions({
|
||||
...validExponentialBackoffOptions,
|
||||
[field]: value,
|
||||
})).toThrow(`${field} must be not less than 0`);
|
||||
}
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that {@link ExponentialBackoff.validateOptions} rejects jitter below 0 or above 1.
|
||||
*/
|
||||
const testExponentialBackoffValidateOptionsRejectsInvalidJitter = (): void => {
|
||||
// Define our test cases with each value being less than 0 or greater than 1
|
||||
const invalidJitterCases: Array<{ value: number }> = [{ value: -0.1 }, { value: 1.1 }];
|
||||
|
||||
// Iterate through the test cases and expect an error to be thrown
|
||||
for (const { value } of invalidJitterCases) {
|
||||
expect(() =>
|
||||
ExponentialBackoff.validateOptions({
|
||||
...validExponentialBackoffOptions,
|
||||
jitter: value,
|
||||
})).toThrow('jitter must be not less than 0 or greater than 1');
|
||||
}
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that {@link ExponentialBackoff.validateOptions} rejects non-finite values such as Infinity.
|
||||
*/
|
||||
const testExponentialBackoffValidateOptionsRejectsNonFiniteValues = (): void => {
|
||||
// Define our test cases with each value being Infinity
|
||||
const nonFiniteCases = [
|
||||
{ field: 'maxDelay', value: Infinity },
|
||||
{ field: 'maxAttempts', value: Infinity },
|
||||
{ field: 'baseDelay', value: Infinity },
|
||||
{ field: 'growthRate', value: Infinity },
|
||||
{ field: 'jitter', value: Infinity },
|
||||
] as const;
|
||||
|
||||
// Iterate through the test cases and expect an error to be thrown
|
||||
for (const { field, value } of nonFiniteCases) {
|
||||
expect(() =>
|
||||
ExponentialBackoff.validateOptions({
|
||||
...validExponentialBackoffOptions,
|
||||
[field]: value,
|
||||
})).toThrow(`${field} must be a finite number`);
|
||||
}
|
||||
};
|
||||
|
||||
/**
|
||||
* Tests that {@link ExponentialBackoff.validateOptions} rejects NaN, which is also non-finite.
|
||||
*/
|
||||
const testExponentialBackoffValidateOptionsRejectsNaN = (): void => {
|
||||
// Define our test cases with each value being NaN
|
||||
const nanCases = [
|
||||
{ field: 'maxDelay', value: Number.NaN },
|
||||
{ field: 'maxAttempts', value: Number.NaN },
|
||||
{ field: 'baseDelay', value: Number.NaN },
|
||||
{ field: 'growthRate', value: Number.NaN },
|
||||
{ field: 'jitter', value: Number.NaN },
|
||||
] as const;
|
||||
|
||||
// Iterate through the test cases and expect an error to be thrown
|
||||
for (const { field, value } of nanCases) {
|
||||
expect(() =>
|
||||
ExponentialBackoff.validateOptions({
|
||||
...validExponentialBackoffOptions,
|
||||
[field]: value,
|
||||
})).toThrow(`${field} must be a finite number`);
|
||||
}
|
||||
};
|
||||
|
||||
const runTests = async (): Promise<void> => {
|
||||
test('ExponentialBackoff.run: delegates to a new instance using default options', testExponentialBackoffRunUsesDefaultOptions);
|
||||
test('ExponentialBackoff.run: retries and succeeds with partial options', testExponentialBackoffRunWithPartialOptions);
|
||||
test('ExponentialBackoff.run: uses the instance default onError when omitted', testExponentialBackoffInstanceRunUsesDefaultOnError);
|
||||
test('ExponentialBackoff: returns the result on first success', testExponentialBackoffSucceedsOnFirstAttempt);
|
||||
test('ExponentialBackoff: retries until the function succeeds', testExponentialBackoffRetriesUntilSuccess);
|
||||
test('ExponentialBackoff: calls onError for each failed attempt', testExponentialBackoffCallsOnErrorForEachFailure);
|
||||
test(
|
||||
'ExponentialBackoff: throws ExponentialBackoffMaxRetriesHitError when max attempts are exhausted',
|
||||
testExponentialBackoffThrowsMaxRetriesHitErrorWhenExhausted,
|
||||
);
|
||||
test('ExponentialBackoff: wraps non-Error throws before calling onError', testExponentialBackoffWrapsNonErrorThrows);
|
||||
test('ExponentialBackoff: succeeds and aborts with abort signal', testExponentialBackoffRunSuccessAndAbortSignal);
|
||||
test('ExponentialBackoff: aborts with abort signal', testExponentialBackoffRunWithAbortSignal);
|
||||
test('ExponentialBackoff: aborts with aborted string creates error', testExponentialBackoffRunAbortedStringCreatesError);
|
||||
test('ExponentialBackoff: works via from and instance run', testExponentialBackoffFromAndInstanceRun);
|
||||
test('ExponentialBackoff: retries indefinitely when maxAttempts is 0', testExponentialBackoffRetriesIndefinitelyWhenMaxAttemptsIsZero);
|
||||
test('ExponentialBackoff: increases delay exponentially between attempts', testExponentialBackoffIncreasesDelayExponentially);
|
||||
test('ExponentialBackoff: caps delay at maxDelay', testExponentialBackoffCapsDelayAtMaxDelay);
|
||||
test('ExponentialBackoff: subtracts jitter from the capped delay', testExponentialBackoffAppliesJitter);
|
||||
test('ExponentialBackoff.validateOptions: accepts valid options', testExponentialBackoffValidateOptionsAcceptsValidOptions);
|
||||
test('ExponentialBackoff.validateOptions: rejects negative values', testExponentialBackoffValidateOptionsRejectsNegativeValues);
|
||||
test('ExponentialBackoff.validateOptions: rejects invalid jitter', testExponentialBackoffValidateOptionsRejectsInvalidJitter);
|
||||
test('ExponentialBackoff.validateOptions: rejects Infinity', testExponentialBackoffValidateOptionsRejectsNonFiniteValues);
|
||||
test('ExponentialBackoff.validateOptions: rejects NaN', testExponentialBackoffValidateOptionsRejectsNaN);
|
||||
};
|
||||
|
||||
await runTests();
|
||||
Reference in New Issue
Block a user