api-error-handling

Define an error-handling middleware with four parameters (err, req, res, next) registered after all routes. It reads err.status and err.code, builds a standardized JSON error response with the request ID, logs 5xx errors, and sends the response with the appropriate status code.

Create a CircuitBreaker class tracking failure count and state (CLOSED, OPEN, HALF_OPEN) with a lock for thread safety. After the failure threshold is reached it opens, then transitions to HALF_OPEN after the recovery timeout to test if the service recovered.

A standard error response should include an error code, human-readable message, HTTP status, request ID for traceability, timestamp, and optional field-level details for validation errors. Never expose stack traces to clients.

Yes, Flask supports registering error handlers for custom exception classes via @app.errorhandler(ApiError). The handler converts the exception into a JSON response with its code, message, status, and request ID, logging at warning or error level based on severity.

Use retry with exponential backoff for transient failures like network timeouts or rate limits when calling external APIs. Add jitter to the delay to avoid thundering herd, and cap retries so persistent failures surface instead of looping indefinitely.