Create CachedBlob class

3 files changed, 43 insertions, 38 deletions

diff --git a/app/models/blobs_service.rb b/app/models/blobs_service.rb
index 5469c3a9a3e..5e4adc3a95d 100644
--- a/app/models/blobs_service.rb
+++ b/app/models/blobs_service.rb
@@ -1,57 +1,55 @@
-# This is a wrapper for Blob model.
+# This is a thin caching wrapper class for Blob model.
 # It acts as a thin layer which caches lightweight information
 # based on the blob content (which is not cached).
 class BlobsService
+  CACHED_METHODS = %i(id raw_size size readable_text? name raw_binary? binary? path
+                      external_storage_error? stored_externally? total_lines).freeze
+
   def initialize(project, content_sha, path)
     @project = project
     @content_sha = content_sha
     @path = path
   end
 
+  # We need blobs data (content) in order to highlight diffs (see
+  # Gitlab::Diff:Highlight), and we don't cache this (Blob#data) on Redis,
+  # mainly because it's a quite heavy information to cache for every blob.
+  #
+  # Therefore, in this scenario (no highlight yet) we use the uncached blob
+  # version.
+  def fetch(highlighted:)
+    return unless content_sha
+    return uncached_blob unless highlighted
+
+    cache_exists? ? cached_blob : uncached_blob
+  end
+
+
   def write_cache_if_empty
     return unless content_sha
     return if cache_exists?
     return unless uncached_blob
 
-    blob_cache = { id: uncached_blob.id,
-                   raw_size: uncached_blob.raw_size,
-                   size: uncached_blob.size,
-                   readable_text: uncached_blob.readable_text?,
-                   name: uncached_blob.name,
-                   binary: uncached_blob.binary?,
-                   path: uncached_blob.path,
-                   external_storage_error: uncached_blob.external_storage_error?,
-                   stored_externally: uncached_blob.stored_externally?,
-                   total_lines: uncached_blob.total_lines }
-
-    cache.write(cache_key, blob_cache, expires_in: 1.week)
+    cache.write(cache_key, cacheable_blob_hash, expires_in: 1.week)
   end
 
   def clear_cache
     cache.delete(cache_key)
   end
 
-  # We need blobs data (content) in order to highlight diffs (see
-  # Gitlab::Diff:Highlight), and we don't cache this (Blob#data) on Redis,
-  # mainly because it's a quite heavy information to cache for every blob.
-  #
-  # Therefore, in this scenario (no highlight yet) we use the uncached blob
-  # version.
-  def blob(highlighted:)
-    return unless content_sha
-    return uncached_blob unless highlighted
+  private
+
+  attr_reader :content_sha
 
-    if cache_exists?
-      # TODO: This can be a CachedBlob
-      Hashie::Mash.new(read_cache)
-    else
-      uncached_blob
+  def cacheable_blob_hash
+    CACHED_METHODS.each_with_object({}) do |_method, hash|
+      hash[_method] = uncached_blob.public_send(_method)
     end
   end
 
-  private
-
-  attr_reader :content_sha
+  def cached_blob
+    CachedBlob.new(read_cache)
+  end
 
   def uncached_blob
     @uncached_blob ||= Blob.lazy(@project, @content_sha, @path)&.itself
diff --git a/app/models/cached_blob.rb b/app/models/cached_blob.rb
new file mode 100644
index 00000000000..fa95ecc70bd
--- /dev/null
+++ b/app/models/cached_blob.rb
@@ -0,0 +1,11 @@
+class CachedBlob
+  delegate *BlobsService::CACHED_METHODS, to: :@blob_cache
+
+  def initialize(blob_cache)
+    @blob_cache = Hashie::Mash.new(blob_cache)
+  end
+
+  def load_all_data!
+    # no-op
+  end
+end
diff --git a/lib/gitlab/diff/file.rb b/lib/gitlab/diff/file.rb
index 39a64502f67..95e2df007fd 100644
--- a/lib/gitlab/diff/file.rb
+++ b/lib/gitlab/diff/file.rb
@@ -104,23 +104,19 @@ module Gitlab
       end
 
       def new_blob_service
-        BlobsService.new(repository.project,
-                         new_content_sha,
-                         file_path)
+        BlobsService.new(repository.project, new_content_sha, file_path)
       end
 
       def old_blob_service
-        BlobsService.new(repository.project,
-                         old_content_sha,
-                         file_path)
+        BlobsService.new(repository.project, old_content_sha, file_path)
       end
 
       def new_blob
-        new_blob_service.blob(highlighted: highlighted?)
+        new_blob_service.fetch(highlighted: highlighted?)
       end
 
       def old_blob
-        old_blob_service.blob(highlighted: highlighted?)
+        old_blob_service.fetch(highlighted: highlighted?)
       end
 
       def content_sha