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Async Request Not Usable

URI: https://docs.ankatech.co/errors/async-not-usable

HTTP Status: 503 Service Unavailable

When you see this

The server began processing your request asynchronously, but the underlying HTTP request/response pair became unusable before the task finished (e.g., the client disconnected or an async timeout expired). Because the operation cannot be completed, the API returns a 503 error indicating a temporary service unavailability.

Common Causes

  • The client closed the tab, lost network connectivity, or cancelled the request while waiting for a long-running endpoint (streaming, SSE, file export, etc.).

  • A reverse proxy or load balancer terminated the connection before the async operation completed.

  • The server exceeded the configured async timeout (spring.mvc.async.request-timeout), causing Spring to clear the request context.

  • Keep-alive or idle-timeout settings on an intermediary (Nginx, ELB, Envoy, API Gateway) were lower than the endpoint's execution time.

How to Resolve

  1. Review the response detail for clues such as "Async context completed" or "Request expired".

  2. If the endpoint legitimately runs for a long time, consider:

    • Increasing idle / read timeouts on proxies, gateways, or load balancers.

  3. Ensure intermediary timeouts (proxy, gateway, LB) exceed your longest expected request duration.

  4. Retry the request once connectivity or timeout settings have been adjusted---the 503 status indicates a condition that should be temporary.

If you continue to see a 503 error after these steps, please consult the full API Reference.