discourse/app/services/random_topic_selector.rb

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1.9 KiB
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class RandomTopicSelector
BACKFILL_SIZE = 3000
BACKFILL_LOW_WATER_MARK = 500
def self.backfill(category=nil)
exclude = category.try(:topic_id)
# don't leak private categories into the "everything" group
user = category ? CategoryFeaturedTopic.fake_admin : nil
options = {
per_page: SiteSetting.category_featured_topics,
visible: true,
no_definitions: true
}
options[:except_topic_ids] = [category.topic_id] if exclude
options[:category] = category.id if category
query = TopicQuery.new(user, options)
results = query.latest_results.order('RANDOM()')
.where(closed: false, archived: false)
.limit(BACKFILL_SIZE)
.reorder('RANDOM()')
.pluck(:id)
key = cache_key(category)
results.each do |id|
$redis.rpush(key, id)
end
$redis.expire(key, 2.days)
results
end
def self.next(count, category=nil)
key = cache_key(category)
results = []
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return results if count < 1
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results = $redis.multi do
$redis.lrange(key, 0, count-1)
$redis.ltrim(key, count, -1)
end
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if !results.is_a?(Array) # Redis is in readonly mode
results = $redis.lrange(key, 0, count-1)
else
results = results[0]
end
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results.map!(&:to_i)
left = count - results.length
backfilled = false
if left > 0
ids = backfill(category)
backfilled = true
results += ids[0...count]
results.uniq!
results = results[0...count]
end
if !backfilled && $redis.llen(key) < BACKFILL_LOW_WATER_MARK
Scheduler::Defer.later("backfill") do
backfill(category)
end
end
results
end
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def self.clear_cache!
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$redis.keys('random_topic_cache*').each{|k| $redis.del k}
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end
def self.cache_key(category=nil)
"random_topic_cache_#{category.try(:id)}"
end
end