Do not include highlighted_diff_email css for each note for new review email
What does this MR do and why?
In #355027 (closed), we discovered that Premailer::Adapter::Nokogiri#to_inline_css uses 25.93 seconds (51%) and it allocates a lot of memory: #355027 (comment 880321527)
After debugging Premailer::Adapter::Nokogiri#to_inline_css, I found that the biggest issue is that we are including highlighted_diff_email.css for each note/comment.
This means that in the case when a review contains 65 diff_discussion notes/comments, we will include mentioned CSS 65 times.
This will cause the Premailer Nokogiri adapter to search the whole HTML Dom object for each selector from that included css - (there are 81 of them). This action will then repeat 65 times, allocating 65x time more memory and time.
Premailer::Adapter::Nokogiri#to_inline_css took total of 26.55 seconds to execute for 65 diff discussions.
Click to expand
| selector | total time | count |
|---|---|---|
| .diff-line-num | 0.9784890040755272 | 65 |
| .code > tr | 0.8081630114465952 | 65 |
| .diff-line-num.new | 0.628456000238657 | 65 |
| .line_content | 0.5463110134005547 | 65 |
| .diff-line-num.old | 0.443707000464201 | 65 |
| .line_content.new | 0.4226210117340088 | 65 |
| .code | 0.42036799155175686 | 65 |
| .n | .37347900308668613 | 65 |
| .line_content.old | 0.3633930031210184 | 65 |
| .o | 0.34669999964535236 | 65 |
| .line_content.new > .line > span.idiff | 0.34396199882030487 | 65 |
| .line_content.new > .line > span > span.idiff | 0.33864900656044483 | 65 |
| .k | 0.33754899725317955 | 65 |
| .line_content.old > .line > span > span.idiff | 0.3354520071297884 | 65 |
| .line_content.old > .line > span.idiff | 0.3346880041062832 | 65 |
| .line_content.match | 0.32732499577105045 | 65 |
| .... | .... | .... |
This MR makes sure to include highlighted_diff_email css only once.
Results with fix
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How to set up and validate locally highlighted_diff_email
Numbered steps to set up and validate the change are strongly suggested.
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Related to #355027 (closed)