[Fleet] Fix 500 in Fleet API when request to product versions endpoin…

…t throws ECONNREFUSED (elastic#172850)

## Summary

Network-level errors will cause `fetch` to `throw` rather than resolving
with a status code. This PR updates our logic to handle this case for
airgapped environments where `ECONNREFUSED` style errors squash HTTP
requests at the DNS level.

x-pack/plugins/fleet/server/services/agents/versions.test.ts

@@ -179,4 +179,29 @@ describe('getAvailableVersions', () => {
     expect(mockedFetch).toBeCalledTimes(1);
     expect(res2).not.toContain('300.0.0');
   });
+
+  it('should gracefully handle 400 errors when fetching from product versions API', async () => {
+    mockKibanaVersion = '300.0.0';
+    mockedReadFile.mockResolvedValue(`["8.1.0", "8.0.0", "7.17.0", "7.16.0"]`);
+    mockedFetch.mockResolvedValue({
+      status: 400,
+      text: 'Bad request',
+    } as any);
+
+    const res = await getAvailableVersions({ ignoreCache: true });
+
+    // Should sort, uniquify and filter out versions < 7.17
+    expect(res).toEqual(['8.1.0', '8.0.0', '7.17.0']);
+  });
+
+  it('should gracefully handle network errors when fetching from product versions API', async () => {
+    mockKibanaVersion = '300.0.0';
+    mockedReadFile.mockResolvedValue(`["8.1.0", "8.0.0", "7.17.0", "7.16.0"]`);
+    mockedFetch.mockRejectedValue('ECONNREFUSED');
+
+    const res = await getAvailableVersions({ ignoreCache: true });
+
+    // Should sort, uniquify and filter out versions < 7.17
+    expect(res).toEqual(['8.1.0', '8.0.0', '7.17.0']);
+  });
 });

x-pack/plugins/fleet/server/services/agents/versions.ts

@@ -24,6 +24,7 @@ const AGENT_VERSION_BUILD_FILE = 'x-pack/plugins/fleet/target/agent_versions_lis
 
 // Endpoint maintained by the web-team and hosted on the elastic website
 const PRODUCT_VERSIONS_URL = 'https://www.elastic.co/api/product_versions';
+const MAX_REQUEST_TIMEOUT = 60 * 1000; // Only attempt to fetch product versions for one minute total
 
 // Cache available versions in memory for 1 hour
 const CACHE_DURATION = 1000 * 60 * 60;
@@ -118,21 +119,29 @@ async function fetchAgentVersionsFromApi() {
     },
   };
 
-  const response = await pRetry(() => fetch(PRODUCT_VERSIONS_URL, options), { retries: 1 });
-  const rawBody = await response.text();
-
-  // We need to handle non-200 responses gracefully here to support airgapped environments where
-  // Kibana doesn't have internet access to query this API
-  if (response.status >= 400) {
-    logger.debug(`Status code ${response.status} received from versions API: ${rawBody}`);
-    return [];
-  }
+  try {
+    const response = await pRetry(() => fetch(PRODUCT_VERSIONS_URL, options), {
+      retries: 1,
+      maxRetryTime: MAX_REQUEST_TIMEOUT,
+    });
+    const rawBody = await response.text();
+
+    // We need to handle non-200 responses gracefully here to support airgapped environments where
+    // Kibana doesn't have internet access to query this API
+    if (response.status >= 400) {
+      logger.debug(`Status code ${response.status} received from versions API: ${rawBody}`);
+      return [];
+    }
 
-  const jsonBody = JSON.parse(rawBody);
+    const jsonBody = JSON.parse(rawBody);
 
-  const versions: string[] = (jsonBody.length ? jsonBody[0] : [])
-    .filter((item: any) => item?.title?.includes('Elastic Agent'))
-    .map((item: any) => item?.version_number);
+    const versions: string[] = (jsonBody.length ? jsonBody[0] : [])
+      .filter((item: any) => item?.title?.includes('Elastic Agent'))
+      .map((item: any) => item?.version_number);
 
-  return versions;
+    return versions;
+  } catch (error) {
+    logger.debug(`Error fetching available versions from API: ${error.message}`);
+    return [];
+  }
 }