Merge branch 'exponential-backoff' into sse-and-backoff

This commit is contained in:
2026-08-07 05:48:29 +00:00
6 changed files with 384 additions and 235 deletions
+40
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@@ -40,3 +40,43 @@ export class ExponentialBackoffStoppedRetriesError extends Error {
this.name = 'ExponentialBackoffStoppedRetriesError';
}
}
/**
* Error thrown when an exponential backoff option is too small
*/
export class ExponentialBackoffNumberTooSmallError extends Error {
constructor(option: string, value: number, min: number) {
super(`Exponential backoff option "${option}" is too small. Must be at least ${min}. Received value: ${value}`);
this.name = 'ExponentialBackoffNumberTooSmallError';
}
}
/**
* Error thrown when an exponential backoff option is out of bounds
*/
export class ExponentialBackoffNumberOutOfBoundsError extends Error {
constructor(option: string, value: number, min: number, max: number) {
super(`Exponential backoff option "${option}" is out of bounds. Must be between ${min} and ${max}. Received value: ${value}`);
this.name = 'ExponentialBackoffNumberOutOfBoundsError';
}
}
/**
* Error thrown when an exponential backoff option is an invalid infinite integer
*/
export class ExponentialBackoffNumberNotFiniteError extends Error {
constructor(option: string, value: number) {
super(`Exponential backoff option "${option}" is invalid. Must be a finite number. Received value: ${value}`);
this.name = 'ExponentialBackoffNumberNotFiniteError';
}
}
/**
* Error thrown when an exponential backoff option is not an integer
*/
export class ExponentialBackoffNonIntegerError extends Error {
constructor(option: string, value: number) {
super(`Exponential backoff option "${option}" is invalid. Must be an integer. Received value: ${value}`);
this.name = 'ExponentialBackoffNonIntegerError';
}
}
+256 -230
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@@ -1,233 +1,12 @@
import { ExponentialBackoffStoppedRetriesError, ExponentialBackoffMaxRetriesHitError } from './errors.ts';
/**
* Exponential backoff is a technique used to retry a function after a delay.
*
* The delay increases exponentially with each attempt, up to a maximum delay.
*
* The jitter is a random amount of time subtracted from the delay to prevent thundering herd problems.
*
* The growth rate is the factor by which the delay increases with each attempt.
*/
export class ExponentialBackoff {
readonly #options: ExponentialBackoffOptions;
/**
* Creates a new exponential-backoff instance.
*
* Unspecified options use the defaults listed below.
*
* @param options - Exponential-backoff configuration overrides.
* @param options.maxDelay - Maximum delay between retries. Default: `10_000` ms.
* @param options.maxAttempts - Maximum number of attempts; `0` retries indefinitely. Default: `10`.
* @param options.baseDelay - Delay used as the basis for the first retry. Default: `1_000` ms.
* @param options.growthRate - Multiplier applied to the delay after each attempt. Default: `2`.
* @param options.jitter - Maximum proportional reduction subtracted from each delay (01). Default: `0.1`.
*/
constructor(options: Partial<ExponentialBackoffOptions> = {}) {
this.#options = {
maxDelay: 10_000,
maxAttempts: 10,
baseDelay: 1_000,
growthRate: 2,
jitter: 0.1,
...options,
};
ExponentialBackoff.validateOptions(this.#options);
}
/**
* Create a new ExponentialBackoff instance
*
* @param config - The configuration for the exponential backoff
* @returns The ExponentialBackoff instance
*/
static from(config?: Partial<ExponentialBackoffOptions>): ExponentialBackoff {
const backoff = new ExponentialBackoff(config);
return backoff;
}
/**
* Run the function with exponential backoff
*
* @param taskFn - The function to run
* @param onError - The callback to call when an error occurs
* @param options - The configuration for the exponential backoff
*
* @throws An {@link ExponentialBackoffMaxRetriesHitError} with all the errors that were thrown by the task function
* @throws An {@link ExponentialBackoffStoppedRetriesError} if the abort signal is activated
*
* @returns The result of the function
*/
static run<T>(
taskFn: (callbackParameters: ExponentialBackoffCallbackParameters) => Promise<T>,
onError = (_error: Error): void => {},
options?: Partial<ExponentialBackoffOptions>,
): Promise<T> {
const backoff = ExponentialBackoff.from(options);
return backoff.run(taskFn, onError);
}
/**
* Calculate the delay before we should attempt to retry
*
* @param options - The configuration for the exponential backoff
* @param attempt - The current attempt number
* @returns The time in milliseconds before another attempt should be made
*/
public static calculateDelay(options: ExponentialBackoffOptions, attempt: number): number {
// Get the power of the growth rate
const power = options.growthRate ** attempt;
// Get the delay before jitter or limit
const rawDelay = options.baseDelay * power;
// Cap the delay to the maximum. Do this before the jitter so jitter does not become larger than delay
const cappedDelay = Math.min(rawDelay, options.maxDelay);
// Get a random number for the amount to "jitter" the delay by
const jitterAmount = Math.random();
// Calculate the jitter
const jitter = jitterAmount * options.jitter * cappedDelay;
// Subtract the jitter from the delay
return cappedDelay - jitter;
}
/**
* Validate the options for the exponential backoff
*
* @param options - The options to validate
*
* @throws An error if the options are invalid
*/
public static validateOptions(options: ExponentialBackoffOptions): void {
// Validate the max delay is a finite number not less than 0
if (!Number.isFinite(options.maxDelay)) {
throw new Error('maxDelay must be a finite number');
}
if (options.maxDelay < 0) {
throw new Error('maxDelay must be not less than 0');
}
// Validate the max attempts is a finite number not less than 0
if (!Number.isFinite(options.maxAttempts)) {
throw new Error('maxAttempts must be a finite number');
}
if (options.maxAttempts < 0) {
throw new Error('maxAttempts must be not less than 0');
}
// Validate the base delay is a finite number not less than 0
if (!Number.isFinite(options.baseDelay)) {
throw new Error('baseDelay must be a finite number');
}
if (options.baseDelay < 0) {
throw new Error('baseDelay must be not less than 0');
}
// Validate the growth rate is a finite number not less than 0
if (!Number.isFinite(options.growthRate)) {
throw new Error('growthRate must be a finite number');
}
if (options.growthRate < 0) {
throw new Error('growthRate must be not less than 0');
}
// Validate the jitter is a finite number not less than 0 or greater than 1
if (!Number.isFinite(options.jitter)) {
throw new Error('jitter must be a finite number');
}
if (options.jitter < 0 || options.jitter > 1) {
throw new Error('jitter must be not less than 0 or greater than 1');
}
}
/**
* Run the function with exponential backoff
*
* If the function fails but we have not hit the max attempts, the error will be passed to the onError callback
* and the function will be retried with an exponential delay
*
* 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
*
* @param taskFn - The function to run
* @param onError - The callback to call when an error occurs
*
* @throws An {@link ExponentialBackoffMaxRetriesHitError} with all the errors that were thrown by the task function
* @throws An {@link ExponentialBackoffStoppedRetriesError} if the abort signal is activated
*
* @returns The result of the function
*/
async run<T>(
taskFn: (callbackParameters: ExponentialBackoffCallbackParameters) => Promise<T>,
onError = (_error: Error): void => {},
): Promise<T> {
// Initialize an abort signal to allow the task function to be aborted
const abortController = new AbortController();
const stopRetries = abortController.abort.bind(abortController);
// Initialize an empty array to store the errors
const errors: Error[] = [];
// Initialize the attempt counter
let attempt = 0;
// If the max attempts is 0, we should continue indefinitely.
const unlimitedAttempts = this.#options.maxAttempts === 0;
// Loop until we succeed, hit the max attempts, or the abort signal is activated
while (true) {
try {
// Await the promise before returning so its execution context remains in the try-catch
// If we didn't await, this `run` function would successfully return and any errors would not be caught here.
return await taskFn({ stopRetries });
} catch (error) {
// Store the error in case we fail every attempt
const errorInstance = error instanceof Error ? error : new Error(`${error}`);
onError(errorInstance);
// If we have unlimited attempts, don't append this to the errors array to prevent a memory leak.
if (!unlimitedAttempts) {
errors.push(errorInstance);
}
}
// Calculate the count for next attempt. Do this now so we can exit before waiting and before running the next attempt.
const nextAttemptCount = attempt + 1;
const nextAttemptExceedsMaxAttempts = nextAttemptCount >= this.#options.maxAttempts;
// If the next attempt exceeds the max attempts, break out of the loop
if (!unlimitedAttempts && nextAttemptExceedsMaxAttempts) {
break;
}
// Check if the abort signal has been aborted
if (abortController.signal.aborted) {
// Throw an error if the abort signal has been aborted
throw new ExponentialBackoffStoppedRetriesError(abortController.signal.reason);
}
// Wait before going to the next attempt
const delay = ExponentialBackoff.calculateDelay(this.#options, attempt);
await new Promise((resolve) => setTimeout(resolve, delay));
attempt++;
}
// We completed the loop without ever succeeding. Throw an ExponentialBackoffMaxRetriesHitError with all the errors we got
throw new ExponentialBackoffMaxRetriesHitError(errors);
}
}
import {
ExponentialBackoffStoppedRetriesError,
ExponentialBackoffMaxRetriesHitError,
ExponentialBackoffNonIntegerError,
ExponentialBackoffNumberTooSmallError,
ExponentialBackoffNumberOutOfBoundsError,
ExponentialBackoffNumberNotFiniteError,
} from './errors.ts';
import { isWithinBounds } from './misc.ts';
export type ExponentialBackoffOptions = {
@@ -273,3 +52,250 @@ export type ExponentialBackoffStopRetriesFunction = (reason: unknown) => void;
export type ExponentialBackoffCallbackParameters = {
stopRetries: ExponentialBackoffStopRetriesFunction;
};
/**
* Exponential backoff is a technique used to retry a function after a delay.
*
* The delay increases exponentially with each attempt, up to a maximum delay.
*
* The jitter is a random amount of time subtracted from the delay to prevent thundering herd problems.
*
* The growth rate is the factor by which the delay increases with each attempt.
*/
export class ExponentialBackoff {
readonly #options: ExponentialBackoffOptions;
/**
* Creates a new exponential-backoff instance.
*
* Unspecified options use the defaults listed below.
*
* @param options - Exponential-backoff configuration overrides.
* @param options.maxDelay - Maximum delay between retries. Default: `10_000` ms.
* @param options.maxAttempts - Maximum number of attempts; `0` retries indefinitely. Default: `10`.
* @param options.baseDelay - Delay used as the basis for the first retry. Default: `1_000` ms.
* @param options.growthRate - Multiplier applied to the delay after each attempt. Default: `2`.
* @param options.jitter - Maximum proportional reduction subtracted from each delay (01). Default: `0.1`.
*
* @throws An {@link ExponentialBackoffNumberNotFiniteError} if a provided option is not a finite number
* @throws An {@link ExponentialBackoffNumberOutOfBoundsError} if a provided option is out of bounds
* @throws An {@link ExponentialBackoffNumberTooSmallError} if a provided option is too small
* @throws An {@link ExponentialBackoffNonIntegerError} if a provided option is not an integer
*/
constructor(options: Partial<ExponentialBackoffOptions> = {}) {
this.#options = {
maxDelay: 10_000,
maxAttempts: 10,
baseDelay: 1_000,
growthRate: 2,
jitter: 0.1,
...options,
};
ExponentialBackoff.validateOptions(this.#options);
}
/**
* Create a new ExponentialBackoff instance
*
* @param config - The configuration for the exponential backoff
*
* @throws An {@link ExponentialBackoffNumberNotFiniteError} if a provided option is not a finite number
* @throws An {@link ExponentialBackoffNumberOutOfBoundsError} if a provided option is out of bounds
* @throws An {@link ExponentialBackoffNumberTooSmallError} if a provided option is too small
* @throws An {@link ExponentialBackoffNonIntegerError} if a provided option is not an integer
*
* @returns The ExponentialBackoff instance
*/
public static from(config?: Partial<ExponentialBackoffOptions>): ExponentialBackoff {
const backoff = new ExponentialBackoff(config);
return backoff;
}
/**
* Run the function with exponential backoff
*
* @param taskFn - The function to run
* @param onError - The callback to call when an error occurs
* @param options - The configuration for the exponential backoff
*
* @throws An {@link ExponentialBackoffMaxRetriesHitError} with all the errors that were thrown by the task function
* @throws An {@link ExponentialBackoffStoppedRetriesError} if the abort signal is activated
*
* @returns The result of the function
*/
public static run<T>(
taskFn: (callbackParameters: ExponentialBackoffCallbackParameters) => Promise<T>,
onError = (_error: Error): void => {},
options?: Partial<ExponentialBackoffOptions>,
): Promise<T> {
const backoff = ExponentialBackoff.from(options);
return backoff.run(taskFn, onError);
}
/**
* Calculate the delay before we should attempt to retry
*
* @param options - The configuration for the exponential backoff
* @param attempt - The current attempt number
* @returns The time in milliseconds before another attempt should be made
*/
public static calculateDelay(options: ExponentialBackoffOptions, attempt: number): number {
// Get the power of the growth rate
const power = options.growthRate ** attempt;
// Get the delay before jitter or limit
const rawDelay = options.baseDelay * power;
// Cap the delay to the maximum. Do this before the jitter so jitter does not become larger than delay
const cappedDelay = Math.min(rawDelay, options.maxDelay);
// Get a random number for the amount to "jitter" the delay by
const jitterAmount = Math.random();
// Calculate the jitter
const jitter = jitterAmount * options.jitter * cappedDelay;
// Subtract the jitter from the delay
return cappedDelay - jitter;
}
/**
* Validate the options for the exponential backoff
*
* @param options - The options to validate
*
* @throws {@link ExponentialBackoffNumberNotFiniteError} if a provided option is not a finite number
* @throws {@link ExponentialBackoffNonIntegerError} if a provided option is not an integer
* @throws {@link ExponentialBackoffNumberOutOfBoundsError} if a provided option is out of bounds
* @throws {@link ExponentialBackoffNumberTooSmallError} if a provided option is too small
*/
public static validateOptions(options: ExponentialBackoffOptions): void {
/** Validate the value is finite, throwing an {@link ExponentialBackoffInvalidInfiniteIntegerError} if the value is infinite */
const assertIsFinite = (key: string, value: number): void => {
if (!Number.isFinite(value)) {
throw new ExponentialBackoffNumberNotFiniteError(key, value);
}
};
/** Validate the value is an integer, throwing a {@link ExponentialBackoffNonIntegerError} if it is not an integer */
const assertIsInteger = (key: string, value: number): void => {
if (!Number.isInteger(value)) {
throw new ExponentialBackoffNonIntegerError(key, value);
}
};
/** Validate the value is greater than the minimum, throwing a {@link ExponentialBackoffNumberTooSmallError} if it is not */
const assertIsHigherThan = (key: string, value: number, min: number): void => {
if (value < min) {
throw new ExponentialBackoffNumberTooSmallError(key, value, min);
}
};
/** Validate the value is within the bounds, throwing a {@link ExponentialBackoffNumberOutOfBoundsError} if it is not within the bounds */
const assertIsWithinBounds = (key: string, value: number, min: number, max: number): void => {
if (!isWithinBounds(value, min, max)) {
throw new ExponentialBackoffNumberOutOfBoundsError(key, value, min, max);
}
};
// Validate the max delay
assertIsFinite('maxDelay', options.maxDelay);
assertIsHigherThan('maxDelay', options.maxDelay, 0);
// Validate the max attempts
assertIsFinite('maxAttempts', options.maxAttempts);
assertIsInteger('maxAttempts', options.maxAttempts);
assertIsHigherThan('maxAttempts', options.maxAttempts, 0);
// Validate the base delay
assertIsFinite('baseDelay', options.baseDelay);
assertIsHigherThan('baseDelay', options.baseDelay, 0);
// Validate the growth rate
assertIsFinite('growthRate', options.growthRate);
assertIsHigherThan('growthRate', options.growthRate, 0);
// Validate the jitter
assertIsFinite('jitter', options.jitter);
assertIsWithinBounds('jitter', options.jitter, 0, 1);
}
/**
* Run the function with exponential backoff
*
* If the function fails but we have not hit the max attempts, the error will be passed to the onError callback
* and the function will be retried with an exponential delay
*
* 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
*
* @param taskFn - The function to run
* @param onError - The callback to call when an error occurs
*
* @throws An {@link ExponentialBackoffMaxRetriesHitError} with all the errors that were thrown by the task function
* @throws An {@link ExponentialBackoffStoppedRetriesError} if the abort signal is activated
*
* @returns The result of the function
*/
public async run<T>(
taskFn: (callbackParameters: ExponentialBackoffCallbackParameters) => Promise<T>,
onError = (_error: Error): void => {},
): Promise<T> {
// Initialize an abort signal to allow the task function to be aborted
const abortController = new AbortController();
const stopRetries = abortController.abort.bind(abortController);
// Initialize an empty array to store the errors
const errors: Error[] = [];
// Initialize the attempt counter
let attempt = 0;
// If the max attempts is 0, we should continue indefinitely.
const unlimitedAttempts = this.#options.maxAttempts === 0;
// Loop until we succeed, hit the max attempts, or the abort signal is activated
while (true) {
try {
// Await the promise before returning so its execution context remains in the try-catch
// If we didn't await, this `run` function would successfully return and any errors would not be caught here.
return await taskFn({ stopRetries });
} catch (error) {
// Store the error in case we fail every attempt
const errorInstance = error instanceof Error ? error : new Error(`${error}`);
onError(errorInstance);
// If we have unlimited attempts, don't append this to the errors array to prevent a memory leak.
if (!unlimitedAttempts) {
errors.push(errorInstance);
}
}
// Calculate the count for next attempt. Do this now so we can exit before waiting and before running the next attempt.
const nextAttemptCount = attempt + 1;
const nextAttemptExceedsMaxAttempts = nextAttemptCount >= this.#options.maxAttempts;
// If the next attempt exceeds the max attempts, break out of the loop
if (!unlimitedAttempts && nextAttemptExceedsMaxAttempts) {
break;
}
// Check if the abort signal has been activated
if (abortController.signal.aborted) {
// Throw an error if the abort signal has been activated
throw new ExponentialBackoffStoppedRetriesError(abortController.signal.reason);
}
// Wait before going to the next attempt
const delay = ExponentialBackoff.calculateDelay(this.#options, attempt);
await new Promise((resolve) => setTimeout(resolve, delay));
attempt++;
}
// We completed the loop without ever succeeding. Throw an ExponentialBackoffMaxRetriesHitError with all the errors we got
throw new ExponentialBackoffMaxRetriesHitError(errors);
}
}
+1
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@@ -1,3 +1,4 @@
export * from './errors.ts';
export * from './event-emitter.ts';
export * from './exponential-backoff.ts';
export * from './extended-json.ts';
+17
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@@ -1,3 +1,20 @@
/**
* Validate the value is within the bounds, returning true if it is within the bounds, false otherwise
*
* @param value - The value to validate
* @param min - The minimum value
* @param max - The maximum value
*
* @returns True if the value is within the bounds, false otherwise
*/
export const isWithinBounds = (value: number, min: number, max: number): boolean => {
if (value < min || value > max) {
return false;
}
return true;
};
/**
* Tries to execute an async function and handles any errors that occur.
* @param fn - The function to execute.