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Utils

safeAction

Implements deduplication and short-term caching for concurrent asynchronous actions.
Advanced Utility: This function is designed for high-concurrency environments to solve the Cache Stampede problem by deduplicating in-flight asynchronous operations.

The safeAction utility is a tool for managing concurrent asynchronous operations. It prevents duplicate execution of expensive actions (like refreshing a token or fetching a singleton resource) by using a "leader" pattern.

Behavior

When multiple concurrent calls are made with the same token:

  1. Cache Check: If a fresh result exists in the short-term cache, it's returned immediately.
  2. Lock Check: If the action is already being executed by another caller, the current caller waits for that same promise to resolve.
  3. Leader Execution: If no lock or cache exists, the current caller becomes the "leader", starts the execution, and shares the resulting promise with all subsequent callers.

Definition

promiseLocker.ts
export async function safeAction<T>(
    token: string,
    action: () => Promise<T>,
    recentResultsTTL = 3000,
    log: pino.Logger
): Promise<T>

Parameters

ParameterTypeDefaultDescription
tokenstring-A unique key used for locking and caching the operation.
action() => Promise<T>-The asynchronous function to perform if no lock or cache is found.
recentResultsTTLnumber3000Duration (in ms) to cache the completed result after the lock is released.
logpino.Logger-A Pino logger instance for tracking execution flow and cache status.

Example Usage

This is perfect for preventing redundant heavy requests to external APIs or databases.

example.ts
import { safeAction } from '@riavzon/utils'
import pino from 'pino'

const logger = pino();

async function refreshToken() {
  console.log('Refreshing token...');
  return await api.post('/refresh');
}

// Even if 100 requests call this simultaneously:
// Only ONE 'Refreshing token...' log will appear.
// All 100 callers will receive the exact same result.
const token = await safeAction('auth-refresh', refreshToken, 5000, logger);
This utility is especially powerful in microservices or high-concurrency environments to ensure consistency and reduce load on external services.

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