{"record":{"id":"ba47cccf1281a22a","repo":"wasmerio/wasmer","slug":"timeout-while-downloading-response-body","errorCode":null,"errorMessage":"Timeout while downloading response body","messagePattern":"Timeout while downloading response body","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"lib/wasix/src/http/reqwest.rs","lineNumber":121,"sourceCode":"                        res = stream.try_next() => {\n                            match res {\n                                Ok(Some(chunk)) => {\n                                    buf.extend_from_slice(&chunk);\n                                    chunk_count += 1;\n                                }\n                                Ok(None) => {\n                                    break 'OUTER;\n                                }\n                                Err(e) => {\n                                    return Err(e.into());\n                                }\n                            }\n                        }\n\n                        _ = &mut timeout => {\n                            if chunk_count == 0 {\n                                tracing::warn!(timeout= \"timeout while downloading response body\");\n                                return Err(anyhow::anyhow!(\"Timeout while downloading response body\"));\n                            } else {\n                                tracing::debug!(downloaded_body_size_bytes=%buf.len(), \"download progress\");\n                                // Timeout, but chunks were downloaded, so\n                                // just continue with a fresh timeout.\n                                continue 'OUTER;\n                            }\n                        }\n                    }\n                }\n            }\n\n            buf\n        } else {\n            response.bytes().await?.to_vec()\n        };\n        #[cfg(feature = \"js\")]\n        let data = response.bytes().await?.to_vec();\n","sourceCodeStart":103,"sourceCodeEnd":139,"githubUrl":"https://github.com/wasmerio/wasmer/blob/8c4b9ee9d33fb2068863fbb3d328683e7e6ff7f5/lib/wasix/src/http/reqwest.rs#L103-L139","documentation":"The WASIX reqwest-based HTTP host implementation streams the response body in chunks under a per-chunk timeout in `request`. If the timeout fires before any chunk has been downloaded (chunk_count == 0), it aborts with 'Timeout while downloading response body'. If some chunks were already received, it resets the timeout and keeps going — so this specifically means nothing at all arrived within the window.","triggerScenarios":"WASM module issues an HTTP request whose response body never starts arriving within the timeout: server hangs after sending headers, network stalls, or a very slow/hung upstream behind a proxy.","commonSituations":"Backend service in the WASM app hangs (deadlocked DB query); firewall drops the connection silently after headers; huge slow upload on a poor mobile connection; proxy holding the response without streaming it.","solutions":["Retry the request — transient network stalls are the most common cause and succeed on retry.","Check the remote server's health/logs: it likely accepted the request but never wrote a body.","Verify network connectivity and that no firewall/NAT is silently dropping established connections.","If behind a proxy, confirm the proxy streams chunked responses instead of buffering.","Increase the body-download timeout in the WASIX HTTP configuration if the server is legitimately slow."],"exampleFix":"// before: single attempt\nlet resp = http.request(req).await?;\n// after: retry on body-download timeout\nlet resp = match http.request(req.clone()).await {\n    Ok(r) => r,\n    Err(e) if e.to_string().contains(\"Timeout while downloading response body\") => {\n        tokio::time::sleep(Duration::from_secs(1)).await;\n        http.request(req).await?\n    }\n    Err(e) => return Err(e.into()),\n};","handlingStrategy":"retry","validationCode":"// preflight: probe the endpoint with a short timeout before the real call\nasync fn reachable(url: &str) -> bool {\n    reqwest::Client::new()\n        .head(url)\n        .timeout(Duration::from_secs(5))\n        .send()\n        .await\n        .map(|r| r.status().is_success())\n        .unwrap_or(false)\n}","typeGuard":null,"tryCatchPattern":"async fn request_with_retry(http: &Http, req: Request) -> Result<Response> {\n    const MAX: usize = 3;\n    for attempt in 1..=MAX {\n        match http.request(req.clone()).await {\n            Ok(r) => return Ok(r),\n            Err(e) if e.to_string().contains(\"Timeout while downloading response body\") && attempt < MAX => {\n                tokio::time::sleep(Duration::from_millis(500 * attempt as u64)).await;\n            }\n            Err(e) => return Err(e.into()),\n        }\n    }\n    unreachable!()\n}","preventionTips":["Wrap WASIX HTTP calls in retry-with-backoff for transient stalls","Set explicit timeouts on the guest-side HTTP client","Monitor backend services for hung requests (slow endpoints trigger this)","Verify firewalls/NAT don't silently drop idle established connections"],"tags":["network","timeout","http","wasm","wasix"],"backgroundTag":"response-body-timeout","analyzedSha":"8c4b9ee9d33fb2068863fbb3d328683e7e6ff7f5","analyzedAt":"2026-09-01T23:06:31.009Z","contentChangedAt":null,"schemaVersion":2},"datasetVersion":"2026-09-09T06:17:21.866Z"}