Improve error handling in case the UI-containers are not accessible

spec/file_caching_test.js

@@ -268,6 +268,51 @@ describe('File caching service', function () {
     expect(response5.text).to.equal('second')
   })
 
+  it('checks again for files after an error occurred', async function () {
+    // we have example.js in both files. the first one will be overwritten and therefore not be called
+    mockFetch({
+      'http://ui-server': {
+        '/manifest.json': generateSimpleViteManifest({
+          'example.js': { }
+        }),
+        '/example.js': td.when(td.func()(td.matchers.anything())).thenReturn(
+          new Response('UI-container not available', { headers: { 'content-type': 'text/plain' }, status: 503 }),
+          new Response('Now available', { headers: { 'content-type': 'text/plain' } })
+        )
+      }
+    })
+    app = await mockApp()
+
+    const response1 = await request(app.server).get('/example.js')
+    expect(response1.statusCode).to.equal(404)
+
+    const response2 = await request(app.server).get('/example.js')
+    expect(response2.statusCode).to.equal(200)
+    expect(response2.text).to.equal('Now available')
+  })
+
+  it('does not check again, when a 404 occurred', async function () {
+    // we have example.js in both files. the first one will be overwritten and therefore not be called
+    mockFetch({
+      'http://ui-server': {
+        '/manifest.json': generateSimpleViteManifest({
+          'example.js': { }
+        }),
+        '/example.js': td.when(td.func()(td.matchers.anything())).thenReturn(
+          new Response('Not found', { headers: { 'content-type': 'text/plain' }, status: 404 }),
+          new Response('Now found', { headers: { 'content-type': 'text/plain' } })
+        )
+      }
+    })
+    app = await mockApp()
+
+    const response1 = await request(app.server).get('/example.js')
+    expect(response1.statusCode).to.equal(404)
+
+    const response2 = await request(app.server).get('/example.js')
+    expect(response2.statusCode).to.equal(404)
+  })
+
   it('only fetches files once, even when requested simultanously', async function () {
     let spy
     mockFetch({

src/errors.js

-export class NotFoundError extends Error {}
+export class NotFoundError extends Error {
+  constructor (message, options) {
+    super(message, options)
+    this.status = options.status
+  }
+}

src/files.js

@@ -41,7 +41,7 @@ export async function fetchFileWithHeadersFromBaseUrl (path, baseUrl, version) {
   if (!response.ok) {
     if (response.status === 404) logger.trace(`[Files] "${path}" could not be found on "${baseUrl}". Responded with: ${response.status}`)
     else logger.error(`[Files] Unexpected result from file retrieval "${path}" on "${baseUrl}", responded with: ${response.status}`)
-    throw new NotFoundError(`Error fetching file: ${path}`)
+    throw new NotFoundError(`Error fetching file: ${path}`, { status: response.status })
   }
 
   const result = {
@@ -101,7 +101,10 @@ export function getFile ({ version, path }) {
       }
     }
 
-    const dataFromServer = await fetchFileWithHeaders({ version, path })
+    const dataFromServer = await fetchFileWithHeaders({ version, path }).catch(err => {
+      if (err.status !== 404) delete cache.getCache()[key]
+      throw err
+    })
     if (redis.isEnabled()) {
       logger.debug(`[Files] Store in redis: ${key}`)
       const { body, ...rest } = dataFromServer