@nodelibraries/circuit-breaker

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CircuitBreaker ​

Main class for managing circuit breakers.

Constructor ​

typescript
constructor(eventHandlers?: EventHandlers)

Creates a new instance of CircuitBreaker.

Parameters ​

  • eventHandlers (optional): Object containing event handler functions

Example ​

typescript
const circuitBreaker = new CircuitBreaker({
  timeout: () => console.error('Request timeout'),
  failure: () => console.error('Request failed'),
  open: () => console.error('Circuit breaker opened'),
});

Methods ​

execute ​

typescript
execute<T>(params: CircuitBreakerParams<T>): Promise<T>

Executes a request function with circuit breaker protection.

Parameters ​

  • params: Object containing:
    • level (optional): The level of the circuit breaker (CircuitBreakerLevel)
    • name: The name of the circuit breaker (string)
    • requestFn: The request function to be wrapped by the circuit breaker
    • args (optional): Arguments to be passed to the requestFn
    • fallbackFn (optional): Fallback function to be executed in case of failure
    • fallbackFnArgs (optional): Arguments to be passed to the fallbackFn
    • options (optional): Custom circuit breaker options

Returns ​

  • Promise<T>: A promise that resolves to the result of the requestFn

Example ​

typescript
const result = await circuitBreaker.execute({
  level: CircuitBreakerLevel.External,
  name: 'fetchUserData',
  requestFn: fetchUserData,
  args: [userId],
  fallbackFn: fallbackUserData,
  options: {
    timeout: 5000,
    errorThresholdPercentage: 50,
  },
});

getCircuitBreakerStats ​

typescript
getCircuitBreakerStats(): Record<string, any>

Gets statistics for all circuit breakers.

Returns ​

  • Record<string, any>: An object containing statistics for all circuit breakers

Example ​

typescript
const stats = circuitBreaker.getCircuitBreakerStats();
console.log(stats);
// {
//   'External::fetchUserData': {
//     fires: 100,
//     successes: 95,
//     failures: 5,
//     ...
//   }
// }

Event Handlers ​

The following event handlers can be provided in the constructor:

  • fire?: () => void - Emitted when a request is made
  • reject?: () => void - Emitted when a request is rejected
  • timeout?: () => void - Emitted when a request times out
  • success?: () => void - Emitted when a request succeeds
  • failure?: () => void - Emitted when a request fails
  • open?: () => void - Emitted when the circuit opens
  • close?: () => void - Emitted when the circuit closes
  • halfOpen?: () => void - Emitted when the circuit transitions to half-open
  • fallback?: () => void - Emitted when a fallback function is executed
  • semaphoreLocked?: () => void - Emitted when the semaphore is locked
  • healthCheckFailed?: () => void - Emitted when a health check fails
  • shutdown?: () => void - Emitted when the circuit breaker shuts down
  • cacheHit?: () => void - Emitted when a cached response is used
  • cacheMiss?: () => void - Emitted when a cache miss occurs

See Also ​