[fix] delayed_sidekiq race condition

CHANGELOG.md

@@ -7,6 +7,7 @@
 ### Changes
 
 ### Bugs Fixed
+* [#937](https://github.com/toptal/chewy/pull/937): Fix for race condition while using the `delayed_sidekiq` strategy. Also, fix for Redis bloating in case of reindexing error ([@skcc321](https://github.com/skcc321))
 
 ## 7.5.1 (2024-01-30)
 

Gemfile

@@ -4,6 +4,7 @@ gem 'activerecord'
 
 gem 'activejob', require: false
 gem 'sidekiq', require: false
+gem 'redis', require: false
 
 gem 'kaminari-core', require: false
 

README.md

@@ -776,9 +776,12 @@ Chewy.settings[:sidekiq] = {queue: :low}
 
 #### `:delayed_sidekiq`
 
-It accumulates ids of records to be reindexed during the latency window in redis and then does the reindexing of all accumulated records at once.
-The strategy is very useful in case of frequently mutated records.
-It supports `update_fields` option, so it will try to select just enough data from the DB
+It accumulates IDs of records to be reindexed during the latency window in Redis and then performs the reindexing of all accumulated records at once. 
+This strategy is very useful in the case of frequently mutated records. 
+It supports the `update_fields` option, so it will attempt to select just enough data from the database.
+
+Keep in mind, this strategy does not guarantee reindexing in the event of Sidekiq worker termination or an error during the reindexing phase. 
+This behavior is intentional to prevent continuous growth of Redis db.
 
 There are three options that can be defined in the index:
 ```ruby

lib/chewy/strategy/delayed_sidekiq.rb

@@ -9,11 +9,11 @@ class DelayedSidekiq < Sidekiq
       # leak and potential flaky tests.
       def self.clear_timechunks!
         ::Sidekiq.redis do |redis|
-          timechunk_sets = redis.smembers(Chewy::Strategy::DelayedSidekiq::Scheduler::ALL_SETS_KEY)
-          break if timechunk_sets.empty?
+          keys_to_delete = redis.keys("#{Scheduler::KEY_PREFIX}*")
 
-          redis.pipelined do |pipeline|
-            timechunk_sets.each { |set| pipeline.del(set) }
+          # Delete keys one by one
+          keys_to_delete.each do |key|
+            redis.del(key)
           end
         end
       end

lib/chewy/strategy/delayed_sidekiq/scheduler.rb

@@ -12,13 +12,43 @@ class Strategy
     class DelayedSidekiq
       require_relative 'worker'
 
+      LUA_SCRIPT = <<~LUA
+        local timechunk_key = KEYS[1]
+        local timechunks_key = KEYS[2]
+        local serialize_data = ARGV[1]
+        local at = ARGV[2]
+        local ttl = tonumber(ARGV[3])
+
+        local schedule_job = false
+
+        -- Check if the 'sadd?' method is available
+        if redis.call('exists', 'sadd?') == 1 then
+          redis.call('sadd?', timechunk_key, serialize_data)
+        else
+          redis.call('sadd', timechunk_key, serialize_data)
+        end
+
+        -- Set expiration for timechunk_key
+        redis.call('expire', timechunk_key, ttl)
+
+        -- Check if timechunk_key exists in the sorted set
+        if not redis.call('zrank', timechunks_key, timechunk_key) then
+            -- Add timechunk_key to the sorted set
+            redis.call('zadd', timechunks_key, at, timechunk_key)
+            -- Set expiration for timechunks_key
+            redis.call('expire', timechunks_key, ttl)
+            schedule_job = true
+        end
+
+        return schedule_job
+      LUA
+
       class Scheduler
         DEFAULT_TTL = 60 * 60 * 24 # in seconds
         DEFAULT_LATENCY = 10
         DEFAULT_MARGIN = 2
         DEFAULT_QUEUE = 'chewy'
         KEY_PREFIX = 'chewy:delayed_sidekiq'
-        ALL_SETS_KEY = "#{KEY_PREFIX}:all_sets".freeze
         FALLBACK_FIELDS = 'all'
         FIELDS_IDS_SEPARATOR = ';'
         IDS_SEPARATOR = ','
@@ -67,21 +97,8 @@ def initialize(type, ids, options = {})
         #                                                       |      chewy:delayed_sidekiq:CitiesIndex:1679347868
         def postpone
           ::Sidekiq.redis do |redis|
-            # warning: Redis#sadd will always return an Integer in Redis 5.0.0. Use Redis#sadd? instead
-            if redis.respond_to?(:sadd?)
-              redis.sadd?(ALL_SETS_KEY, timechunks_key)
-              redis.sadd?(timechunk_key, serialize_data)
-            else
-              redis.sadd(ALL_SETS_KEY, timechunks_key)
-              redis.sadd(timechunk_key, serialize_data)
-            end
-
-            redis.expire(timechunk_key, ttl)
-
-            unless redis.zrank(timechunks_key, timechunk_key)
-              redis.zadd(timechunks_key, at, timechunk_key)
-              redis.expire(timechunks_key, ttl)
-
+            # do the redis stuff in a single command to avoid concurrency issues
+            if redis.eval(LUA_SCRIPT, keys: [timechunk_key, timechunks_key], argv: [serialize_data, at, ttl])
               ::Sidekiq::Client.push(
                 'queue' => sidekiq_queue,
                 'at' => at + margin,

lib/chewy/strategy/delayed_sidekiq/worker.rb

@@ -6,25 +6,51 @@ class DelayedSidekiq
       class Worker
         include ::Sidekiq::Worker
 
+        LUA_SCRIPT = <<~LUA
+          local type = ARGV[1]
+          local score = tonumber(ARGV[2])
+          local prefix = ARGV[3]
+          local timechunks_key = prefix .. ":" .. type .. ":timechunks"
+
+          -- Get timechunk_keys with scores less than or equal to the specified score
+          local timechunk_keys = redis.call('zrangebyscore', timechunks_key, '-inf', score)
+
+          -- Get all members from the sets associated with the timechunk_keys
+          local members = {}
+          for _, timechunk_key in ipairs(timechunk_keys) do
+              local set_members = redis.call('smembers', timechunk_key)
+              for _, member in ipairs(set_members) do
+                  table.insert(members, member)
+              end
+          end
+
+          -- Remove timechunk_keys and their associated sets
+          for _, timechunk_key in ipairs(timechunk_keys) do
+              redis.call('del', timechunk_key)
+          end
+
+          -- Remove timechunks with scores less than or equal to the specified score
+          redis.call('zremrangebyscore', timechunks_key, '-inf', score)
+
+          return members
+        LUA
+
         def perform(type, score, options = {})
           options[:refresh] = !Chewy.disable_refresh_async if Chewy.disable_refresh_async
 
           ::Sidekiq.redis do |redis|
-            timechunks_key = "#{Scheduler::KEY_PREFIX}:#{type}:timechunks"
-            timechunk_keys = redis.zrangebyscore(timechunks_key, -1, score)
-            members = timechunk_keys.flat_map { |timechunk_key| redis.smembers(timechunk_key) }.compact
+            members = redis.eval(LUA_SCRIPT, keys: [], argv: [type, score, Scheduler::KEY_PREFIX])
 
             # extract ids and fields & do the reset of records
             ids, fields = extract_ids_and_fields(members)
             options[:update_fields] = fields if fields
 
             index = type.constantize
+            # rubocop:disable Style/LambdaCall
             index.strategy_config.delayed_sidekiq.reindex_wrapper.call do
               options.any? ? index.import!(ids, **options) : index.import!(ids)
             end
-
-            redis.del(timechunk_keys)
-            redis.zremrangebyscore(timechunks_key, -1, score)
+            # rubocop:enable Style/LambdaCall
           end
         end
 

spec/chewy/strategy/delayed_sidekiq_spec.rb

@@ -2,17 +2,18 @@
 
 if defined?(Sidekiq)
   require 'sidekiq/testing'
-  require 'mock_redis'
+  require 'redis'
 
   describe Chewy::Strategy::DelayedSidekiq do
     around do |example|
       Chewy.strategy(:bypass) { example.run }
     end
 
     before do
-      redis = MockRedis.new
+      redis = Redis.new
       allow(Sidekiq).to receive(:redis).and_yield(redis)
       Sidekiq::Worker.clear_all
+      described_class.clear_timechunks!
     end
 
     before do
@@ -115,7 +116,7 @@
       context 'one call with update_fields another one without update_fields' do
         it 'does reindex of all fields' do
           Timecop.freeze do
-            expect(CitiesIndex).to receive(:import!).with([other_city.id, city.id]).once
+            expect(CitiesIndex).to receive(:import!).with([city.id, other_city.id]).once
             scheduler = Chewy::Strategy::DelayedSidekiq::Scheduler.new(CitiesIndex, [city.id], update_fields: ['name'])
             scheduler.postpone
             scheduler = Chewy::Strategy::DelayedSidekiq::Scheduler.new(CitiesIndex, [other_city.id])
@@ -128,7 +129,7 @@
       context 'both calls with different update fields' do
         it 'deos reindex with union of fields' do
           Timecop.freeze do
-            expect(CitiesIndex).to receive(:import!).with([other_city.id, city.id], update_fields: %w[description name]).once
+            expect(CitiesIndex).to receive(:import!).with([city.id, other_city.id], update_fields: %w[name description]).once
             scheduler = Chewy::Strategy::DelayedSidekiq::Scheduler.new(CitiesIndex, [city.id], update_fields: ['name'])
             scheduler.postpone
             scheduler = Chewy::Strategy::DelayedSidekiq::Scheduler.new(CitiesIndex, [other_city.id], update_fields: ['description'])