API超时和流式中断怎么排查：连接、首包和中途断开不是同一问题

$uri = [Uri]$env:BASE_URL
Resolve-DnsName $uri.Host
Test-NetConnection $uri.Host -Port 443 -InformationLevel Detailed
curl.exe -IvsS --connect-timeout 10 "https://$($uri.Host)/" --output NUL
curl.exe --silent --show-error --dump-header response.headers --output response.json --write-out "http=%{http_code} dns=%{time_namelookup}s tcp=%{time_connect}s tls=%{time_appconnect}s ttfb=%{time_starttransfer}s total=%{time_total}s remote_ip=%{remote_ip}\n" --request POST "$env:BASE_URL/responses" --header "Authorization: Bearer $env:OPENAI_API_KEY" --header "Content-Type: application/json" --data-raw '{"model":"<MODEL_ID>","input":"Reply with OK."}'

HOST=api.openai.com
dig +short "$HOST" || nslookup "$HOST"
nc -vz -w 10 "$HOST" 443
openssl s_client -connect "$HOST:443" -servername "$HOST" </dev/null
curl --silent --show-error --dump-header response.headers --output response.json --write-out "http=%{http_code} dns=%{time_namelookup}s tcp=%{time_connect}s tls=%{time_appconnect}s ttfb=%{time_starttransfer}s total=%{time_total}s remote_ip=%{remote_ip}\n" --request POST "$BASE_URL/responses" --header "Authorization: Bearer $OPENAI_API_KEY" --header "Content-Type: application/json" --data '{"model":"<MODEL_ID>","input":"Reply with OK."}'

const baseUrl = process.env.BASE_URL || "https://api.openai.com/v1";
const idleTimeoutMs = 45_000;
const startedAt = Date.now();
const response = await fetch(baseUrl + "/responses", {
  method: "POST",
  headers: {
    Authorization: "Bearer " + process.env.OPENAI_API_KEY,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({ model: process.env.MODEL_ID, input: "Reply with OK.", stream: true })
});
console.log({ status: response.status, contentType: response.headers.get("content-type"), requestId: response.headers.get("x-request-id") || "<not-returned>" });
if (!response.ok || !response.body) throw new Error("HTTP failed before SSE body: " + response.status);

const reader = response.body.getReader();
const decoder = new TextDecoder();
let buffer = "";
let firstChunkAt = null;
let completed = false;

async function readWithIdleTimeout() {
  let timer;
  try {
    return await Promise.race([
      reader.read(),
      new Promise((_, reject) => {
        timer = setTimeout(() => reject(new Error("idle timeout: no SSE bytes for " + idleTimeoutMs + "ms")), idleTimeoutMs);
      })
    ]);
  } finally {
    clearTimeout(timer);
  }
}

while (true) {
  const { value, done } = await readWithIdleTimeout();
  if (done) break;
  if (firstChunkAt === null) {
    firstChunkAt = Date.now();
    console.log({ firstChunkMs: firstChunkAt - startedAt });
  }
  buffer += decoder.decode(value, { stream: true });
  buffer = buffer.replaceAll("\r\n", "\n");
  let boundary;
  while ((boundary = buffer.indexOf("\n\n")) >= 0) {
    const block = buffer.slice(0, boundary);
    buffer = buffer.slice(boundary + 2);
    const data = block.split("\n").filter((line) => line.startsWith("data:")).map((line) => line.slice(5).trim()).join("\n");
    if (!data) continue;
    if (data === "[DONE]") {
      completed = true;
      console.log({ event: "[DONE]", elapsedMs: Date.now() - startedAt });
      continue;
    }
    const event = JSON.parse(data);
    console.log({ event: event.type || "<unknown>", elapsedMs: Date.now() - startedAt });
    if (event.type === "response.completed") completed = true;
    if (event.type === "error") throw new Error("SSE error event received");
  }
}

if (!completed) throw new Error("stream ended without a completion event");
console.log({ completed: true, totalMs: Date.now() - startedAt });