Distrubute statuses as a fan-out-on-write system, with optional precomputing

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Eugen Rochko 2016-03-08 20:16:11 +01:00
parent fe57f6330f
commit 6c4c84b161
9 changed files with 119 additions and 3 deletions

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@ -30,6 +30,7 @@ gem 'rails_autolink'
gem 'doorkeeper'
gem 'rabl'
gem 'oj'
gem 'redis', '~>3.2'
group :development, :test do
gem 'rspec-rails'

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@ -208,6 +208,7 @@ GEM
rake (10.5.0)
rdoc (4.2.2)
json (~> 1.4)
redis (3.2.2)
ref (2.0.0)
responders (2.1.1)
railties (>= 4.2.0, < 5.1)
@ -328,6 +329,7 @@ DEPENDENCIES
rails (= 4.2.5.1)
rails_12factor
rails_autolink
redis (~> 3.2)
rspec-rails
rubocop
sass-rails (~> 5.0)

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@ -22,10 +22,12 @@ class Api::StatusesController < ApiController
end
def home
@statuses = Status.where(account: [current_user.account] + current_user.account.following).order('created_at desc')
feed = Feed.new(:home, current_user.account)
@statuses = feed.get(20, (params[:offset] || 0).to_i)
end
def mentions
@statuses = Status.where(id: Mention.where(account: current_user.account).pluck(:status_id)).order('created_at desc')
feed = Feed.new(:mentions, current_user.account)
@statuses = feed.get(20, (params[:offset] || 0).to_i)
end
end

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@ -2,6 +2,7 @@ class HomeController < ApplicationController
before_action :authenticate_user!
def index
@statuses = Status.where(account: ([current_user.account] + current_user.account.following)).where('reblog_of_id IS NULL OR account_id != ?', current_user.account.id).order('created_at desc')
feed = Feed.new(:home, current_user.account)
@statuses = feed.get(20, (params[:offset] || 0).to_i)
end
end

27
app/models/feed.rb Normal file
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@ -0,0 +1,27 @@
class Feed
def initialize(type, account)
@type = type
@account = account
end
def get(limit, offset = 0)
unhydrated = redis.zrevrange(key, offset, limit)
status_map = Hash.new
# If we're after most recent items and none are there, we need to precompute the feed
return PrecomputeFeedService.new.(@type, @account).take(limit) if unhydrated.empty? && offset == 0
Status.where(id: unhydrated).each { |status| status_map[status.id.to_s] = status }
return unhydrated.map { |id| status_map[id] }
end
private
def key
"feed:#{@type}:#{@account.id}"
end
def redis
$redis
end
end

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@ -67,5 +67,6 @@ class Status < ActiveRecord::Base
after_create do
self.account.stream_entries.create!(activity: self)
FanOutOnWriteService.new.(self)
end
end

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@ -0,0 +1,46 @@
class FanOutOnWriteService < BaseService
MAX_FEED_SIZE = 800
# Push a status into home and mentions feeds
# @param [Status] status
def call(status)
replied_to_user = status.reply? ? status.thread.account : nil
# Deliver to local self
push(:home, status.account.id, status) if status.account.local?
# Deliver to local followers
status.account.followers.each do |follower|
next if (status.reply? && !follower.following?(replied_to_user)) || !follower.local?
push(:home, follower.id, status)
end
# Deliver to local mentioned
status.mentions.each do |mentioned_account|
next unless mentioned_account.local?
push(:mentions, mentioned_account.id, status)
end
end
private
def push(type, receiver_id, status)
redis.zadd(key(type, receiver_id), status.created_at.to_i, status.id)
trim(type, receiver_id)
end
def trim(type, receiver_id)
return unless redis.zcard(key(type, receiver_id)) > MAX_FEED_SIZE
last = redis.zrevrange(key(type, receiver_id), MAX_FEED_SIZE - 1, MAX_FEED_SIZE - 1)
redis.zremrangebyscore(key(type, receiver_id), '-inf', "(#{last.last}")
end
def key(type, id)
"feed:#{type}:#{id}"
end
def redis
$redis
end
end

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@ -0,0 +1,35 @@
class PrecomputeFeedService < BaseService
MAX_FEED_SIZE = 800
# Fill up a user's home/mentions feed from DB and return it
# @param [Symbol] type :home or :mentions
# @param [Account] account
# @return [Array]
def call(type, account)
statuses = send(type.to_s, account).order('created_at desc').limit(MAX_FEED_SIZE)
statuses.each { |status| push(type, account.id, status) }
statuses
end
private
def push(type, receiver_id, status)
redis.zadd(key(type, receiver_id), status.created_at.to_i, status.id)
end
def home(account)
Status.where(account: [account] + account.following)
end
def mentions(account)
Status.where(id: Mention.where(account: account).pluck(:status_id))
end
def key(type, id)
"feed:#{type}:#{id}"
end
def redis
$redis
end
end

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@ -0,0 +1 @@
$redis = Redis.new(host: ENV['REDIS_HOST'] || 'localhost', port: ENV['REDIS_PORT'] || 6379)