DEV: Add optional s3_stale_while_revalidate and s3_max_age for uploads (#36298)

With this change, S3's `stale-while-revalidate` and `max-age` response
directives can be controlled.

By default, off for `stale-while-revalidate`, and both are hidden site
settings.

config/site_settings.yml

@@ -2212,6 +2212,16 @@ files:
   s3_access_key_id:
     default: ""
     secret: true
+  s3_max_age:
+    default: 31556952
+    min: 60
+    max: 31556952
+    hidden: true
+  s3_stale_while_revalidate:
+    default: 31556952
+    min: 60
+    max: 31556952
+    hidden: true
   s3_secret_access_key:
     default: ""
     secret: true

lib/file_store/s3_store.rb

@@ -90,8 +90,14 @@ module FileStore
       # cache file locally when needed
       cache_file(file, File.basename(path)) if opts[:cache_locally]
 
+      cache_control = "max-age=#{SiteSetting.s3_max_age}, public, immutable"
+      if SiteSetting.s3_stale_while_revalidate != SiteSetting.defaults[:s3_stale_while_revalidate]
+        cache_control =
+          "#{cache_control}, stale-while-revalidate=#{SiteSetting.s3_stale_while_revalidate}"
+      end
+
       options = {
-        cache_control: "max-age=31556952, public, immutable",
+        cache_control: cache_control,
         content_type:
           opts[:content_type].presence || MiniMime.lookup_by_filename(filename)&.content_type,
       }.merge(default_s3_options(secure: opts[:private]))

spec/lib/file_store/s3_store_spec.rb

@@ -54,6 +54,97 @@ RSpec.describe FileStore::S3Store do
         expect(upload.etag).to eq(etag)
       end
 
+      it "adds `stale-while-revalidate` response directive when `s3_stale_while_revalidate` site setting is set" do
+        SiteSetting.s3_stale_while_revalidate = 3600
+        expected_cache_control = "max-age=31556952, public, immutable, stale-while-revalidate=3600"
+        s3_helper.expects(:s3_bucket).returns(s3_bucket).at_least_once
+
+        s3_bucket
+          .expects(:object)
+          .with(regexp_matches(%r{original/\d+X.*/#{upload.sha1}\.png}))
+          .returns(s3_object)
+
+        s3_object
+          .expects(:put)
+          .with(
+            {
+              acl: FileStore::S3Store::CANNED_ACL_PUBLIC_READ,
+              cache_control: expected_cache_control,
+              content_type: "image/png",
+              content_disposition: "inline; filename=\"logo.png\"; filename*=UTF-8''logo.png",
+              body: uploaded_file,
+            },
+          )
+          .returns(Aws::S3::Types::PutObjectOutput.new(etag: "\"#{etag}\""))
+
+        expect(store.store_upload(uploaded_file, upload)).to match(
+          %r{//s3-upload-bucket\.s3\.dualstack\.us-west-1\.amazonaws\.com/original/\d+X.*/#{upload.sha1}\.png},
+        )
+
+        expect(upload.etag).to eq(etag)
+      end
+
+      it "respects `s3_max_age` site setting for cache_control" do
+        SiteSetting.s3_max_age = 60
+        expected_cache_control = "max-age=60, public, immutable"
+        s3_helper.expects(:s3_bucket).returns(s3_bucket).at_least_once
+
+        s3_bucket
+          .expects(:object)
+          .with(regexp_matches(%r{original/\d+X.*/#{upload.sha1}\.png}))
+          .returns(s3_object)
+
+        s3_object
+          .expects(:put)
+          .with(
+            {
+              acl: FileStore::S3Store::CANNED_ACL_PUBLIC_READ,
+              cache_control: expected_cache_control,
+              content_type: "image/png",
+              content_disposition: "inline; filename=\"logo.png\"; filename*=UTF-8''logo.png",
+              body: uploaded_file,
+            },
+          )
+          .returns(Aws::S3::Types::PutObjectOutput.new(etag: "\"#{etag}\""))
+
+        expect(store.store_upload(uploaded_file, upload)).to match(
+          %r{//s3-upload-bucket\.s3\.dualstack\.us-west-1\.amazonaws\.com/original/\d+X.*/#{upload.sha1}\.png},
+        )
+
+        expect(upload.etag).to eq(etag)
+      end
+
+      describe "when default site settings are set" do
+        it "cache_control is `max-age=31556952, public, immutable`" do
+          default_cache_control = "max-age=31556952, public, immutable"
+
+          s3_helper.expects(:s3_bucket).returns(s3_bucket).at_least_once
+
+          s3_bucket
+            .expects(:object)
+            .with(regexp_matches(%r{original/\d+X.*/#{upload.sha1}\.png}))
+            .returns(s3_object)
+
+          s3_object
+            .expects(:put)
+            .with(
+              {
+                acl: FileStore::S3Store::CANNED_ACL_PUBLIC_READ,
+                cache_control: default_cache_control,
+                content_type: "image/png",
+                content_disposition: "inline; filename=\"logo.png\"; filename*=UTF-8''logo.png",
+                body: uploaded_file,
+              },
+            )
+            .returns(Aws::S3::Types::PutObjectOutput.new(etag: "\"#{etag}\""))
+
+          expect(store.store_upload(uploaded_file, upload)).to match(
+            %r{//s3-upload-bucket\.s3\.dualstack\.us-west-1\.amazonaws\.com/original/\d+X.*/#{upload.sha1}\.png},
+          )
+          expect(upload.etag).to eq(etag)
+        end
+      end
+
       describe "when s3_upload_bucket includes folders path" do
         before do
           s3_object.stubs(:put).returns(Aws::S3::Types::PutObjectOutput.new(etag: "\"#{etag}\""))