koala73/worldmonitor · error · ApiError

Duplicate airport delay parameter

Error message

Duplicate airport delay parameter: ${key}

What it means

listAirportDelays rejects any query parameter repeated on the request URL. The handler iterates URL searchParams with a seenParams Set and throws ApiError 400 as soon as a key appears a second time, since repeated params are ambiguous for a seed-only listing endpoint.

Solutions

1. Remove the duplicated query parameter so each key appears at most once in the URL
2. Fix the client's query-string builder to deduplicate keys instead of appending per array item
3. Log ctx.request.url on failure to identify which key is repeated and which code path adds it
4. Add a client-side test asserting the generated query string has unique keys

Example fix

// before
const params = new URLSearchParams();
regions.forEach(r => params.append('rpc', 'list-airport-delays'));
// after
const params = new URLSearchParams({ rpc: 'list-airport-delays' });

const keys = [...new URL(url).searchParams.keys()];
if (new Set(keys).size !== keys.length) throw new Error('duplicate query param');

const hasUniqueParams = (url) => { const ks = [...new URL(url).searchParams.keys()]; return new Set(ks).size === ks.length; };

try { await listAirportDelays(ctx, req); } catch (e) { if (e instanceof ApiError && e.status === 400 && /Duplicate .* parameter/.test(e.message)) { rebuildQueryUnique(); } else throw e; }

When it happens

Trigger: Calling GET .../list-airport-delays with the same query key twice, e.g. ?rpc=list-airport-delays&rpc=list-airport-delays or ?page_size=0&page_size=0 (including arrays serialized as key=a&key=b).

Common situations: Client code building query strings from objects/arrays where a value is a list; URLSearchParams.append called twice; framework serializers that emit repeated keys for array values; proxies rewriting and re-appending params.

Related errors

• Airport delay filters are not supported
• Airport delay page_size must be 0
• deadlineMs must be a positive number
• Expected finite viewport coordinates
• Invalid airport delay route

AI-assisted analysis of koala73/worldmonitor@e586b8b4b8 (2026-09-22). Data as JSON: /api/errors/038bddb4507e1d93. Report an issue: GitHub.

Appendix: source

Thrown at server/worldmonitor/aviation/v1/list-airport-delays.ts:44

// @ts-expect-error — JS module, no declaration file
import { captureSilentError } from '../../../../api/_sentry-edge.js';

const FAA_CACHE_KEY = 'aviation:delays:faa:v1';
const INTL_CACHE_KEY = 'aviation:delays:intl:v3';

const FAA_AIRPORT_SET = new Set(FAA_AIRPORTS);
const INTL_AIRPORT_SET = new Set(AVIATIONSTACK_AIRPORTS);

const ALLOWED_QUERY_PARAMS = new Set(['page_size', 'cursor', 'region', 'min_severity', 'jmespath', '_debug', 'rpc']);

export async function listAirportDelays(
  ctx: ServerContext,
  req: ListAirportDelaysRequest,
): Promise<ListAirportDelaysResponse> {
  const seenParams = new Set<string>();
  for (const [key, value] of new URL(ctx.request.url).searchParams) {
    if (!ALLOWED_QUERY_PARAMS.has(key)) throw new ApiError(400, `Unsupported airport delay parameter: ${key}`, '');
    if (seenParams.has(key)) throw new ApiError(400, `Duplicate airport delay parameter: ${key}`, '');
    seenParams.add(key);
    if (key === 'page_size' && value !== '0') throw new ApiError(400, 'Airport delay page_size must be 0', '');
    if (key === 'rpc' && value !== 'list-airport-delays') throw new ApiError(400, 'Invalid airport delay route', '');
  }
  if ((req.pageSize ?? 0) !== 0 || req.cursor
    || (req.region && req.region !== 'AIRPORT_REGION_UNSPECIFIED')
    || (req.minSeverity && req.minSeverity !== 'FLIGHT_DELAY_SEVERITY_UNSPECIFIED')) {
    throw new ApiError(400, 'Airport delay filters are not supported', '');
  }
  // 1. FAA (US) — seed-only read
  // faaSourceCovered = the seed cache hit AND returned a valid alerts array.
  // A miss/parse-error means we have no telemetry for any FAA airport this
  // tick — we MUST NOT publish synthetic "normal" rows for them. See #3707.
  // PERF: the three inputs below are independent (different Redis keys / an
  // independent fetcher) and merge only afterwards — start them concurrently
  // instead of paying three serial round-trips per request.
  const faaRead = (async (): Promise<{ faaAlerts: AirportDelayAlert[]; faaSourceCovered: boolean; available: boolean }> => {
    let faaAlerts: AirportDelayAlert[] = [];

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