Do not cache uploads for six months by default

Setting a long-term cache header works fine when not using object
storage, or when using object storage with proxy_download enabled. When
using object storage _without_ proxy_download, we send a redirect that's
cached for six months to a signed URL in object storage, but the signed
URL only works for ten minutes. So once those ten minutes are up, the
browser will keep following the (cached) redirect to a dead link.

In future, we could be more sophisticated by setting the TTL based on
the settings we're using. For now, just set this back to the pre-12.4
state of not caching content for longer than 5 minutes.

app/controllers/concerns/uploads_actions.rb

@@ -34,7 +34,7 @@ module UploadsActions
     headers['Pragma'] = ''
 
     ttl, directives = *cache_settings
-    ttl ||= 6.months
+    ttl ||= 0
     directives ||= { private: true, must_revalidate: true }
 
     expires_in ttl, directives

changelogs/unreleased/35337-images-stopped-loading-signed-urls-of-uploads-expire-earlier-than-r.yml

+---
+title: Disable upload HTTP caching to fix case when object storage is enabled and
+  proxy_download is disabled
+merge_request: 19494
+author:
+type: fixed

spec/controllers/uploads_controller_spec.rb

@@ -7,9 +7,9 @@ shared_examples 'content 5 min private cached with revalidation' do
   end
 end
 
-shared_examples 'content long term private cached with revalidation' do
+shared_examples 'content not cached' do
   it 'ensures content will not be cached without revalidation' do
-    expect(subject['Cache-Control']).to eq('max-age=15778476, private, must-revalidate')
+    expect(subject['Cache-Control']).to eq('max-age=0, private, must-revalidate')
   end
 end
 
@@ -490,7 +490,7 @@ describe UploadsController do
             expect(response).to have_gitlab_http_status(200)
           end
 
-          it_behaves_like 'content long term private cached with revalidation' do
+          it_behaves_like 'content not cached' do
             subject do
               get :show, params: { model: 'note', mounted_as: 'attachment', id: note.id, filename: 'dk.png' }
 
@@ -510,7 +510,7 @@ describe UploadsController do
             expect(response).to have_gitlab_http_status(200)
           end
 
-          it_behaves_like 'content long term private cached with revalidation' do
+          it_behaves_like 'content not cached' do
             subject do
               get :show, params: { model: 'note', mounted_as: 'attachment', id: note.id, filename: 'dk.png' }
 
@@ -563,7 +563,7 @@ describe UploadsController do
                 expect(response).to have_gitlab_http_status(200)
               end
 
-              it_behaves_like 'content long term private cached with revalidation' do
+              it_behaves_like 'content not cached' do
                 subject do
                   get :show, params: { model: 'note', mounted_as: 'attachment', id: note.id, filename: 'dk.png' }