discourse/app/jobs/scheduled/periodical_updates.rb
David Taylor d0243f741e
UX: Use dominant color as image loading placeholder (#18248)
We previously had a system which would generate a 10x10px preview of images and add their URLs in a data-small-upload attribute. The client would then use that as the background-image of the `<img>` element. This works reasonably well on fast connections, but on slower connections it can take a few seconds for the placeholders to appear. The act of loading the placeholders can also break or delay the loading of the 'real' images.

This commit replaces the placeholder logic with a new approach. Instead of a 10x10px preview, we use imagemagick to calculate the average color of an image and store it in the database. The hex color value then added as a `data-dominant-color` attribute on the `<img>` element, and the client can use this as a `background-color` on the element while the real image is loading. That means no extra HTTP request is required, and so the placeholder color can appear instantly.

Dominant color will be calculated:
1. When a new upload is created
2. During a post rebake, if the dominant color is missing from an upload, it will be calculated and stored
3. Every 15 minutes, 25 old upload records are fetched and their dominant color calculated and stored. (part of the existing PeriodicalUpdates job)

Existing posts will continue to use the old 10x10px placeholder system until they are next rebaked
2022-09-20 10:28:17 +01:00

59 lines
1.9 KiB
Ruby

# frozen_string_literal: true
module Jobs
# This job will run on a regular basis to update statistics and denormalized data.
# If it does not run, the site will not function properly.
class PeriodicalUpdates < ::Jobs::Scheduled
every 15.minutes
def self.should_update_long_topics?
@call_count ||= 0
@call_count += 1
# once every 6 hours
(@call_count % 24) == 1
end
def execute(args = nil)
# Feature topics in categories
CategoryFeaturedTopic.feature_topics(batched: true)
# Update the scores of posts
args = { min_topic_age: 1.day.ago }
args[:max_topic_length] = 500 unless self.class.should_update_long_topics?
ScoreCalculator.new.calculate(args)
# Forces rebake of old posts where needed, as long as no system avatars need updating
if !SiteSetting.automatically_download_gravatars || !UserAvatar.where("last_gravatar_download_attempt IS NULL").limit(1).first
problems = Post.rebake_old(SiteSetting.rebake_old_posts_count, priority: :ultra_low)
problems.each do |hash|
post_id = hash[:post].id
Discourse.handle_job_exception(hash[:ex], error_context(args, "Rebaking post id #{post_id}", post_id: post_id))
end
end
# rebake out of date user profiles
problems = UserProfile.rebake_old(250)
problems.each do |hash|
user_id = hash[:profile].user_id
Discourse.handle_job_exception(hash[:ex], error_context(args, "Rebaking user id #{user_id}", user_id: user_id))
end
offset = (SiteSetting.max_new_topics).to_i
last_new_topic = Topic.order('created_at desc').offset(offset).select(:created_at).first
if last_new_topic
SiteSetting.min_new_topics_time = last_new_topic.created_at.to_i
end
Category.auto_bump_topic!
Upload.backfill_dominant_colors!(25)
nil
end
end
end