[DEV-2397] Refactor S3 metadata helpers to include retry logic for fetching file…

.changeset/cuddly-zebras-bow.md

@@ -0,0 +1,10 @@
+---
+"nextjs-website": patch
+---
+
+- Added configurable retry logic to `downloadFileAsText()` and `fetchMetadataFromCDN()` functions
+- Implemented exponential backoff with configurable retry attempts and delay timing
+- Added environment variables `CDN_RETRY_ATTEMPTS` (default: 3) and `CDN_RETRY_DELAY_MS` (default: 5000ms)
+- Improved error handling and logging for CDN fetch failures
+- Fixes issues where guide pages would show 404 errors when CloudFront cache was not warmed up
+

apps/nextjs-website/src/helpers/s3Metadata.helpers.ts

@@ -12,54 +12,112 @@ export interface JsonMetadata {
   readonly lastModified?: string;
 }
 
+const delay = (ms: number): Promise<void> =>
+  new Promise((resolve) => setTimeout(resolve, ms));
+
+// Retry configuration - configurable via environment variables
+const RETRY_ATTEMPTS = parseInt(process.env.CDN_RETRY_ATTEMPTS || '3', 10);
+const INITIAL_RETRY_DELAY_MS = parseInt(
+  process.env.CDN_RETRY_DELAY_MS || '5000',
+  10
+);
+
+async function withRetries<T>(
+  operation: () => Promise<T>,
+  operationName: string,
+  fallbackValue: T
+): Promise<T> {
+  // eslint-disable-next-line functional/no-let
+  let lastError: Error | null = null;
+
+  // eslint-disable-next-line functional/no-loop-statements
+  for (let attempt = 1; attempt <= RETRY_ATTEMPTS; attempt++) {
+    // eslint-disable-next-line functional/no-try-statements
+    try {
+      const result = await operation();
+
+      // Log successful retry if this wasn't the first attempt
+      if (attempt > 1) {
+        console.log(
+          `Successfully completed ${operationName} on attempt ${attempt}`
+        );
+      }
+
+      return result;
+    } catch (error) {
+      lastError = error instanceof Error ? error : new Error(String(error));
+      console.error(
+        `Error during ${operationName} (attempt ${attempt}/${RETRY_ATTEMPTS}):`,
+        error
+      );
+
+      // If this isn't the last attempt, wait before retrying
+      if (attempt < RETRY_ATTEMPTS) {
+        const delayMs = INITIAL_RETRY_DELAY_MS * Math.pow(2, attempt - 1); // Exponential backoff
+        console.log(`Retrying in ${delayMs}ms...`);
+        await delay(delayMs);
+      }
+    }
+  }
+
+  console.error(
+    `Failed to complete ${operationName} after ${RETRY_ATTEMPTS} attempts:`,
+    lastError
+  );
+  return fallbackValue;
+}
+
 export async function downloadFileAsText(
   path: string
 ): Promise<string | undefined> {
-  // eslint-disable-next-line functional/no-try-statements
-  try {
-    const url = `${staticContentsUrl}/${path}`;
-    const response = await fetch(url);
-
-    if (!response.ok) {
-      // eslint-disable-next-line functional/no-throw-statements
-      throw new Error(
-        `Failed to download file from ${url}: ${response.statusText}`
-      );
-    }
+  return withRetries(
+    async () => {
+      const url = `${staticContentsUrl}/${path}`;
+      const response = await fetch(url);
 
-    // Read the response body as text
-    const fileContent = await response.text();
-    return fileContent;
-  } catch (error) {
-    console.error('Error downloading file:', error);
-    return;
-  }
+      if (!response.ok) {
+        // eslint-disable-next-line functional/no-throw-statements
+        throw new Error(
+          `Failed to download file from ${url}: ${response.statusText}`
+        );
+      }
+
+      // Read the response body as text
+      return await response.text();
+    },
+    `file download from ${path}`,
+    undefined
+  );
 }
 
 export async function fetchMetadataFromCDN(
   path: string
 ): Promise<readonly JsonMetadata[] | null> {
-  // eslint-disable-next-line functional/no-try-statements
-  try {
-    if (!staticContentsUrl) {
-      // eslint-disable-next-line functional/no-throw-statements
-      throw new Error(
-        'STATIC_CONTENTS_URL is not defined in the environment variables.'
-      );
-    }
-    const response = await fetch(`${staticContentsUrl}/${path}`);
-    if (!response.ok) {
-      // eslint-disable-next-line functional/no-throw-statements
-      throw new Error(
-        `Failed to fetch metadata from ${staticContentsUrl}/${path}: ${response.statusText}`
-      );
-    }
-    const bodyContent = await response.json();
-    return bodyContent as readonly JsonMetadata[];
-  } catch (error) {
-    console.error('Error fetching metadata from CDN:', error);
-    return null;
-  }
+  return withRetries(
+    async () => {
+      if (!staticContentsUrl) {
+        // eslint-disable-next-line functional/no-throw-statements
+        throw new Error(
+          'STATIC_CONTENTS_URL is not defined in the environment variables.'
+        );
+      }
+
+      const url = `${staticContentsUrl}/${path}`;
+      const response = await fetch(url);
+
+      if (!response.ok) {
+        // eslint-disable-next-line functional/no-throw-statements
+        throw new Error(
+          `Failed to fetch metadata from ${url}: ${response.statusText}`
+        );
+      }
+
+      const bodyContent = await response.json();
+      return bodyContent as readonly JsonMetadata[];
+    },
+    `metadata fetch from ${path}`,
+    null
+  );
 }
 
 const S3_GUIDES_METADATA_JSON_PATH =