Hacking Sidekiq for Fun (and Profit) - RubyConf Australia 2014

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Hello!

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I'm Darcy. ! ! @sutto

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If I talk too fast, yell out

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Hacking Sidekiq For Fun!

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(and Profit)

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Sidekiq.explain!

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Background Processing

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Complex logic with many side effects

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Slow logic

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Decouple from Request / Response Lifecycle

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e.g. hit an external API to update expired data on every request

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Background Jobs in Ruby

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backgroundrb

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delayed job

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resque

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sidekiq

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Mike Perham

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Enter Sidekiq

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Threaded

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Actor based concurrency

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Even in MRI, great for network-heavy logic

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Redis for job & metadata storage

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… using same redis layout as Resque.

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Batteries-included

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Built in exception reporting support

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Job retries on failures

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Scheduled Jobs!

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Built in support for many queues

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Built to be extensible

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… we'll talk about this shortly

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Sidekiq Pro

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Not Free but adds powerful features such as: batching, notiﬁcations, metrics and reliable workers.

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Scales from a small number of jobs to many

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But how?

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class HelloPersonWorker! ! include Sidekiq::Worker! sidekiq_options queue: "onboarding"! ! def perform(name)! Rails.logger.info "Saying hello to #{name}"! end! ! end!

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Bonus: Testing is simple - instantiate and test worker class.

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HelloPersonWorker.perform_async "Darcy"! # => "2dbfbc3f28d26be12107db84"

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Sidekiq::Client.push({! "class" => HelloPersonWorker,! "args" => ["Darcy"]! })!

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{! "class": "HelloPersonWorker",! "args": ["Darcy"],! "retry": true,! "queue": "onboarding",! "jid": "2dbfbc3f28d26be12107db84",! "enqueued_at": 1392701981.091299! }

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sadd queues onboarding lpush queue:onboarding [json encoded job]

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Scheduled job?

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Sidekiq::Client.push({! "class" => HelloPersonWorker,! "args" => ["Darcy"],! "at" => Time.now.to_f! })!

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zadd schedule timestamp_1 encoded_json_blob

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Remembering JSON includes Queue Name

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How do we run jobs?

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Sidekiq::Manager

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Sidekiq::Fetch

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… or, more accurately, it's strategy.

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class BasicFetch! def initialize(options)! @strictly_ordered_queues = !!options[:strict]! @queues = options[:queues].map { |q| "queue:#{q}" }! @unique_queues = @queues.uniq! end! ! def retrieve_work! work = Sidekiq.redis { |conn| conn.brpop(*queues_cmd) }! UnitOfWork.new(*work) if work! end! ! # ... more goes here ...! end!

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brpop semantics control how / what we fetch from

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Sidekiq::Fetch::UnitOfWork

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UnitOfWork = Struct.new(:queue, :message) do! def acknowledge! # nothing to do! end! ! def queue_name! queue.gsub(/.*queue:/, '')! end! ! def requeue! Sidekiq.redis do |conn|! conn.rpush("queue:#{queue_name}", message)! end! end! end!

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Job is fetched, run through middleware and “invoked”.

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More around that, but that's the core.

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Making the most of Sidekiq

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Trick #1: Unique Jobs

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Middleware!

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module Sidekiq! module Middleware! module Server! class Logging! ! def call(worker, item, queue)! Sidekiq::Logging.with_context("#{worker.class.to_s} JID-#{item['jid']}") do! begin! start = Time.now! logger.info { "start" }! yield! logger.info { "done: #{elapsed(start)} sec" }! rescue Exception! logger.info { "fail: #{elapsed(start)} sec" }! raise! end! end! end! ! def elapsed(start)! (Time.now - start).to_f.round(3)! end! ! def logger! Sidekiq.logger! end! end! end! end! end!

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def call(worker, item, queue)! Sidekiq::Logging.with_context("#{worker.class.to_s} JID-#{item['jid']}") do! begin! start = Time.now! logger.info { "start" }! yield! logger.info { "done: #{elapsed(start)} sec" }! rescue Exception! logger.info { "fail: #{elapsed(start)} sec" }! raise! end! end! end!

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We want to queue a job, but only if it's not currently queued.

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E.g. Loading external data from an API.

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$ gem install sidekiq-middleware

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Store job uniqueness somehow?

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Client AND Server middleware

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Pushing AND Pulling Jobs

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module Sidekiq! module Middleware! module Client! class UniqueJobs! def call(worker_class, item, queue)! worker_class = worker_class.constantize if worker_class.is_a?(String)! enabled = Sidekiq::Middleware::Helpers.unique_enabled?(worker_class, item)! ! if enabled! expiration = Sidekiq::Middleware::Helpers.unique_exiration(worker_class)! job_id = item['jid']! unique = false! ! # Scheduled! if item.has_key?('at')! # Use expiration period as specified in configuration,! # but relative to job schedule time! expiration += (item['at'].to_i - Time.now.to_i)! end! ! unique_key = Sidekiq::Middleware::Helpers.unique_digest(worker_class, item)! ! Sidekiq.redis do |conn|! conn.watch(unique_key)! ! locked_job_id = conn.get(unique_key)! if locked_job_id && locked_job_id != job_id! conn.unwatch! else! unique = conn.multi do! conn.setex(unique_key, expiration, job_id)! end! end! end! ! yield if unique! else! yield! end! end! end! end! end! end!

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unique_key = Sidekiq::Middleware::Helpers.unique_digest(worker_class, item)! ! Sidekiq.redis do |conn|! conn.watch(unique_key)! ! locked_job_id = conn.get(unique_key)! if locked_job_id && locked_job_id != job_id! conn.unwatch! else! unique = conn.multi do! conn.setex(unique_key, expiration, job_id)! end! end! end! ! yield if unique!

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1. Generate a key from the job structure 2. Check if locked 3. Set lock (with expiry) if not locked

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… with some redis magic

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Hash the JSON of the job, check existence of hash in Redis

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module Sidekiq! module Middleware! module Server! class UniqueJobs! def call(worker_instance, item, queue)! worker_class = worker_instance.class! enabled = Sidekiq::Middleware::Helpers.unique_enabled?(worker_class, item)! ! if enabled! begin! yield! ensure! unless Sidekiq::Middleware::Helpers.unique_manual?(worker_class)! clear(worker_class, item)! end! end! else! yield! end! end! ! def clear(worker_class, item)! Sidekiq.redis do |conn|! conn.del Sidekiq::Middleware::Helpers.unique_digest(worker_class, item)! end! end! end! end! end! end!

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begin! yield! ensure! unless Sidekiq::Middleware::Helpers.unique_manual?(worker_class)! clear(worker_class, item)! end! end!

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1. Run the work 2. Unless user has speciﬁed they'll clear the lock, clear the lock

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Trick #2: Adjusting Running Instances

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Transitions into more powerful territory

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How can we prioritise and schedule work?

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Control number of workers dedicated to a task

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Temporarily pause a queue

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Make queues block others

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Dynamically reorganise workers without process changes

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$ gem install sidekiq-limit_fetch

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Store queue / system metadata in Redis (seperate to jobs)

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Act on settings stored in Redis to control the system state.

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A smart locking algorithm for jobs in Lua

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… running on your Applications Redis server

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Use the lua script to acquire a job instead of brpop

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Custom fetch strategy, a unit of work (to update state) & way to manage metadata.

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Trick #3: Replacing the queue

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… if we can replace the fetcher, what about how we store data?

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$ gem install sidekiq-sqs

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Monkey patches Sidekiq::Client.push to override adding a job

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… but reasonably cleanly switches the fetch strategy

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… but avoid this.

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Final Trick: Spot Instances and AutoScaling

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Spot instances average much, much cheaper

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… but are transient and not guaranteed

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Normal Price for a c1.medium: $0.145 per Hour

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Spot Price for a c1.medium: Average $0.018 per Hour, Peak at $5.00 an hour.

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Perfect for processing big amounts of data / backed up queues

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“I always want at least 5 worker servers, but I can happily jump to 100 if need be”

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… but do it without human intervention

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Sidekiq

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Sidekiq CloudWatch! (Metrics) Publish Sidekiq Queue Sizes

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Sidekiq CloudWatch! (Metrics) Publish Sidekiq Queue Sizes AutoScaling Scale Up / Down based on # of waiting jobs

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Sidekiq CloudWatch! (Metrics) Publish Sidekiq Queue Sizes AutoScaling Scale Up / Down based on # of waiting jobs EC2 Instances Launch Instances w/ Queue or Groups speciﬁed via User Data

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Sidekiq CloudWatch! (Metrics) Publish Sidekiq Queue Sizes AutoScaling Scale Up / Down based on # of waiting jobs EC2 Instances Launch Instances w/ Queue or Groups speciﬁed via User Data Read Queues / Group from the conﬁg, start processing jobs

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System responds to load and instigates measures to help solve it

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I mentioned queue groups, but they're not a sidekiq feature.

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sidekiq.yml conﬁg is run through ERB ﬁrst.

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Write logic based on ENV

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---! queues:! <% if ENV['SIDEKIQ_GROUP'] == 'onboarding' %>! - [hello, 10]! - [world, 5]! <% else %>! - [hello, 2]! - [world, 2]! - [default, 1]! <% end %>!