NetworkingMedium30 XP3 min read
How do you implement automatic retry logic with Dio interceptors?
TL;DR: Add a custom Dio interceptor that catches network errors and retries the request up to N times with exponential backoff. Store the retry count in requestOptions.extra to avoid infinite loops.
Full Answer
Transient network failures (brief connectivity drops, 503 responses) shouldn't fail the user request. A retry interceptor transparently retries and only surfaces the error after N attempts.
- ▸Retry on: connection error, receive timeout, 503 Service Unavailable
- ▸Don't retry on: 4xx errors (client fault), 401 (handle separately with token refresh)
- ▸Exponential backoff: delay = base * 2^attempt to avoid thundering herd
- ▸Max retries: 3 is typical; store in requestOptions.extra['retryCount']
Code Examples
dartRetry interceptor with exponential backoff
Output
// Attempt 1 fails -> wait 1s -> retry // Attempt 2 fails -> wait 2s -> retry // Attempt 3 fails -> wait 4s -> retry // Attempt 4 fails -> propagate error to caller
Common Mistakes
- ✗Retrying 401 responses — the token is invalid; refresh it first, don't just retry
- ✗Not incrementing retryCount — creates infinite retry loop on persistent failures
Interview Tip
💡
Show the exponential backoff formula (1 << retryCount). Mention that jitter (adding random milliseconds) prevents all retrying clients from hammering the server at the same moment after an outage.
#retry#dio-interceptor#exponential-backoff#resilience