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FIX: Use PostgreSQL 'ON CONFLICT' to deal with race condition

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On busy sites, concurrent requests to insert into post_timings can
occur, which was dealt with using Ruby exceptions.

This moves the handling to PostgreSQL which makes it a bit faster,
and prevents a spam of ERROR in the database logs.
This commit is contained in:
Rafael dos Santos Silva 2019-04-29 16:34:42 -03:00
parent bfadb1fabc
commit 526e76ced2
1 changed files with 6 additions and 14 deletions
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20
app/models/post_timing.rb
View File

@ -33,20 +33,12 @@ class PostTiming < ActiveRecord::Base
end end
def self.record_new_timing(args) def self.record_new_timing(args)
begin DB.exec("INSERT INTO post_timings (topic_id, user_id, post_number, msecs)
DB.exec("INSERT INTO post_timings (topic_id, user_id, post_number, msecs) SELECT :topic_id, :user_id, :post_number, :msecs
SELECT :topic_id, :user_id, :post_number, :msecs ON CONFLICT DO NOTHING",
WHERE NOT EXISTS(SELECT 1 FROM post_timings args)
WHERE topic_id = :topic_id # concurrency is hard, we are not running serialized so this can possibly
AND user_id = :user_id # still happen, if it happens we just don't care, its an invalid record anyway
AND post_number = :post_number)",
args)
rescue PG::UniqueViolation
# concurrency is hard, we are not running serialized so this can possibly
# still happen, if it happens we just don't care, its an invalid record anyway
return
end
Post.where(['topic_id = :topic_id and post_number = :post_number', args]).update_all 'reads = reads + 1' Post.where(['topic_id = :topic_id and post_number = :post_number', args]).update_all 'reads = reads + 1'
UserStat.where(user_id: args[:user_id]).update_all 'posts_read_count = posts_read_count + 1' UserStat.where(user_id: args[:user_id]).update_all 'posts_read_count = posts_read_count + 1'
end end