auto-retry for some forecast data

server/scripts/modules/utils/fetch.mjs

@@ -11,9 +11,13 @@ const fetchAsync = async (_url, responseType, _params = {}) => {
 		method: 'GET',
 		mode: 'cors',
 		type: 'GET',
+		retryCount: 0,
 		..._params,
 	};
-		// build a url, including the rewrite for cors if necessary
+	// store original number of retries
+	params.originalRetries = params.retryCount;
+
+	// build a url, including the rewrite for cors if necessary
 	let corsUrl = _url;
 	if (params.cors === true) corsUrl = rewriteUrl(_url);
 	const url = new URL(corsUrl, `${window.location.origin}/`);
@@ -30,7 +34,7 @@ const fetchAsync = async (_url, responseType, _params = {}) => {
 	}
 
 	// make the request
-	const response = await fetch(url, params);
+	const response = await doFetch(url, params);
 
 	// check for ok response
 	if (!response.ok) throw new Error(`Fetch error ${response.status} ${response.statusText} while fetching ${response.url}`);
@@ -47,6 +51,48 @@ const fetchAsync = async (_url, responseType, _params = {}) => {
 	}
 };
 
+// fetch with retry and back-off
+const doFetch = (url, params) => new Promise((resolve, reject) => {
+	fetch(url, params).then((response) => {
+		if (params.retryCount > 0) {
+			// 500 status codes should be retried after a short backoff
+			if (response.status >= 500 && response.status <= 599 && params.retryCount > 0) {
+				// call the "still waiting" function
+				if (typeof params.stillWaiting === 'function' && params.retryCount === params.originalRetries) {
+					params.stillWaiting();
+				}
+				// decrement and retry
+				const newParams = {
+					...params,
+					retryCount: params.retryCount - 1,
+				};
+				return resolve(delay(retryDelay(params.originalRetries - newParams.retryCount), doFetch, url, newParams));
+			}
+			// not 500 status
+			return resolve(response);
+		}
+		// out of retries
+		return resolve(response);
+	})
+		.catch((e) => reject(e));
+});
+
+const delay = (time, func, ...args) => new Promise((resolve) => {
+	setTimeout(() => {
+		resolve(func(...args));
+	}, time);
+});
+
+const retryDelay = (retryNumber) => {
+	switch (retryNumber) {
+	case 1: return 1000;
+	case 2: return 2000;
+	case 3: return 5000;
+	case 4: return 10000;
+	default: return 30000;
+	}
+};
+
 export {
 	json,
 	text,