In order to properly scale our sidekiq workers to the size of our database pool, we came up with a little formula in our configuration
sidekiq.rb
Sidekiq.configure_server do |config|
config.options[:concurrency] = ((ENV['DB_POOL'] || 5).to_i - 1) / workers
end
def workers
... the number of workers configured for our project ...
(ENV['HEROKU_WORKERS'] || 1).to_i
end
We're setting HEROKU_WORKERS by hand, but it would be sweet if there was a way to interrogate the Heroku API from within the application.
Modulo all the things that can happen (workers going up or down, changing the number of workers, etc.), this seems to get us out of the initial problem; where our workers would consume all of the database pool connections, and then start crashing on startup.
The heroku-api gem should provide you this.
https://github.com/heroku/heroku.rb
You should find your API key here: https://dashboard.heroku.com/account
require 'heroku-api'
heroku = Heroku::API.new(api_key: API_KEY)
Total number of current processes:
heroku.get_ps('heroku-app-name').body.count
(You should be able to parse this to get total number of workers... or a count of a specific kind of worker, if you have different kinds defined in your Procfile/Heroku app)
Related
We are using Sidekiq to process a number of backend jobs. One in particular is used very heavily. All I can really say about it is that it sends emails. It doesn't do the email creation (that's a separate job), it just sends them. We spin up a new worker for each email that needs to be sent.
We are trying to upgrade to Ruby 3 and having problems, though. Ruby 2.6.8 has no issues; in 3 (as well as 2.7.3 IIRC), if there is a large number of queued workers, it will get through maybe 20K of them, then it will start hemorrhaging FIFO pipes, on the order of 300-1000 ever 5 seconds or so. Eventually it gets to the ulimit on the system (currently set at 64K) and all sockets/connections fail due to insufficient resources.
In trying to debug this issue I did a run with 90% of what the email worker does entirely commented out, so it does basically nothing except make a couple database queries and do some string templating. I thought I was getting somewhere with that approach, as one run (of 50K+ emails) succeeded without the pipe explosion. However, the next run (identical parameters) did wind up with the runaway pipes.
Profiling with rbspy and ruby-prof did not help much, as they primarily focus on the Sidekiq infrastructure, not the workers themselves.
Looking through our code, I did see that nothing we wrote is ever using IO.* (e.g. IO.popen, IO.select, etc), so I don't see what could be causing the FIFO pipes.
I did see https://github.com/mperham/sidekiq/wiki/Batches#huge-batches, which is not necessarily what we're doing. If you look at the code snippet below, we're basically creating one large batch. I'm not sure whether pushing jobs in bulk as per the link will help with the problem we're having, but I'm about to give it a try once I rework things a bit.
No matter what I do I can't seem to figure out the following:
What is making these pipes? Why are they being created?
What is the condition by which the pipes start getting made exponentially? There are two FIFO pipes that open when we start Sidekiq, but until enough work has been done, we don't see more than 2-6 pipes open generally.
Any advice is appreciated, even along the lines of where to look next, as I'm a bit stumped.
Initializer:
require_relative 'logger'
require_relative 'configuration'
require 'sidekiq-pro'
require "sidekiq-ent"
module Proprietary
unless const_defined?(:ENVIRONMENT)
ENVIRONMENT = ENV['RACK_ENV'] || ENV['RAILS_ENV'] || 'development'
end
# Sidekiq.client_middleware.add Sidekiq::Middleware::Client::Batch
REDIS_URL = if ENV["REDIS_URL"].present?
ENV["REDIS_URL"]
else
"redis://#{ENV["REDIS_SERVER"]}:#{ENV["REDIS_PORT"]}"
end
METRICS = Statsd.new "10.0.9.215", 8125
Sidekiq::Enterprise.unique! unless Proprietary::ENVIRONMENT == "test"
Sidekiq.configure_server do |config|
# require 'sidekiq/pro/reliable_fetch'
config.average_scheduled_poll_interval = 2
config.redis = {
namespace: Proprietary.config.SIDEKIQ_NAMESPACE,
url: Proprietary::REDIS_URL
}
config.server_middleware do |chain|
require 'sidekiq/middleware/server/statsd'
chain.add Sidekiq::Middleware::Server::Statsd, :client => METRICS
end
config.error_handlers << Proc.new do |ex,ctx_hash|
Proprietary.report_exception(ex, "Sidekiq", ctx_hash)
end
config.super_fetch!
config.reliable_scheduler!
end
Sidekiq.configure_client do |config|
config.redis = {
namespace: Proprietary.config.SIDEKIQ_NAMESPACE,
url: Proprietary::REDIS_URL,
size: 15,
network_timeout: 5
}
end
end
Code snippet (sanitized)
def add_targets_to_batch
#target_count = targets.count
queue_counter = 0
batch.jobs do
targets.shuffle.each do |target|
send(campaign_target)
queue_counter += 1
end
end
end
def send(campaign_target)
TargetEmailWorker.perform_async(target[:id],
guid,
is_draft ? target[:email_address] : nil)
begin
Target.where(id: target[:id]).update(send_at: Time.now.utc)
rescue Exception => ex
Proprietary.report_exception(ex, self.class.name, { target_id: target[:id], guid: guid })
end
end
end
First I tried auditing our external connections for connection pooling, etc. That did not help the issue. Eventually I got to the point where I disabled all external connections and let the job run doing virtually nothing outside of a database query and some logging. This allowed one run to complete without issue, but on the second one, the FIFO pipes still grew exponentially after a certain (variable) amount of work was done.
I am exploring the sidekiq API and I am trying to find a way to check for a given queue, how many threads are running at a given moment ( I am using sidekiq limit fetch gem https://github.com/brainopia/sidekiq-limit_fetch , and I would like to be sure the limits I have set up in my config file are respected).
I had a look at workers = Sidekiq::Workers.new which is supposed to hold informations about threads but it doesnt show anything about the number of threads actually.
Is there a way to find out how many threads are running for a specific queue at a given moment in sidekiq ?
I think you are interested into Sidekiq::ProcessSet.new. From the docs:
Sidekiq::ProcessSet gets you access to near real-time (updated every 5 sec) info about the current set of Sidekiq processes running. You can remotely control the processes also:
ps = Sidekiq::ProcessSet.new
ps.size # => 2
ps.each do |process|
p process['busy'] # => 3
p process['hostname'] # => 'myhost.local'
p process['pid'] # => 16131
p process['concurrency'] # => 10 <- this is the number of threads per process
end
I am using Sidekiq (on Heroku with Puma) to send emails asynchronously and would like to use Redis to keep counters and cache models.
RedisCloud's free plan includes 30 connections to Redis. It is not clear to me how to manage:
redis connections used by Sidekiq
redis connections used in models (caching and counters)
Sidekiq Client size is configured like this:
Sidekiq.configure_client do |config|
config.redis = {url: ENV["REDISCLOUD_URL"], size: 3}
end
If I understood this correctly, Puma forks multiple processes, 2 in my case, which will result in:
2 (Puma Workers) * 3 (size) * 1 (Web Dyno) = 6 connections to redis used to push jobs.
Sidekiq Server
With Sidekiq taking 2 connections (or 5 in version 4), setting a concurrency of 10 would default in a server size of 12 or 15.
If I wanted to use all the remaining available connections (30 - 6 = 24), I could set :
Sidekiq.configure_client do |config|
config.redis = { size: 19 }
end
Total redis connections would be 19 + 5 (Sidekiq 4) = 24, and use the default concurrency of 25 would be ok.
As Mike Perham stated generally the concurrency must not be more than (server pool size - 2) * 2.
Now, where it starts to get confusing for me is the use of Redis out of Sidekiq.
# initializers/redis.rb
$redis = Redis.new(:url => uri)
Whenever I use Redis in a model or controller I call like so:
$redis.hincrby("mycounter", "key", 1)
As I understand it, all the puma threads wait on each other on a single Redis connection when $redis.whateverFunction is called.
In this answer What is the best way to use Redis in a Multi-threaded Rails environment? (Puma / Sidekiq), the recommended approach is using the connection_pool gem, related to the Sidekiq Wiki https://github.com/mperham/sidekiq/wiki/Advanced-Options#connection-pooling
require 'connection_pool'
$redis = ConnectionPool.new(size: 10) { Redis.new }
If I understand it right, it that case $redis.whateverFunction would have its own connection pool of 10, and sidekiq its own connection workers pool which would now be set out a new total of 20 redis connections ( 30 (available total) - 10 (redis model connections ), and Sidekiq client and server size would need to be changed.
How do you determine the size of the connection pool (here 10) needed for model/controller redis connections? Since Redis is single-threaded, how does increasing the connection pool actually increases redis operations performance?
Any thoughts on this would be of great help.
Thx!
Redis is single-threaded, but written in pure C, uses an event loop inside and handles connections asynchronously, so connection count does not affect it by much provided the same number of requests. It is capable of handling requests faster than your application can generate them because of network delay, ruby being slower than compiled and optimized C, etc, so you do not need to worry about it being single-threaded.
Increasing number of connections is beneficial for concurrent requests from different threads because there's no need to wait for response to be delivered over network to unlock connection, plus ruby can do parallel IOs.
Also you can tell if pool is too small when connection checkout times become worse than you expect/tolerate and corresponding thread/worker is idling while waiting for it, so benchmark your code and have a good look on your actual usage and behavior patterns.
On the other side i'd advise against using all of the connection count limit, there're times when you might need these extra connections. For example:
for graceful/"zero downtime" dyno restarts ("preboot") you need twice the connections, since old processes are still running for some time
keep at least one free connection for emergency debug as you may want to be able to connect from console/directly and see what data is inside when some unexpected highload comes
I built a small web crawler implemented in two Sidekiq workers: Crawler and Parsing. The Crawler worker will seek for links while Parsing worker will read the page body.
I want to trigger an alert when the crawling/parsing of all pages is complete. Monitoring only the Crawler job is not the best solution since it may have finished but there might be several Parser jobs running.
Having a look at sidekiq-status gem it seems that I cannot dynamically add new jobs to the container for monitoring. E.g. it would be nice to have a "add" method in the following context:
#container = SidekiqStatus::Container.new
# ... for each page url found:
jid = ParserWorker.perform_async(page_url)
#container.add(jid)
The closest to this is to use "SidekiqStatus::Container.load" or "SidekiqStatus::Container.load_multi" however, it is not possible to add new jobs in the container a posteriori.
One solution would be to create as many SidekiqStatus::Container instances as the number of ParserJobs and check if all of them have status == "finished", but I wonder if a more elegant solution exists using these tools.
Any help is appreciated.
You are describing Sidekiq Pro's Batches feature exactly. You can spend a lot of time or some money to solve your problem.
https://github.com/mperham/sidekiq/wiki/Batches
OK, here's a simple solution. Using the sidekiq-status gem, the Crawler worker keeps track of the jobs IDs for the Parser jobs and halts if any Parser job is still busy (using the SidekiqStatus::Container instance to check job status).
def perform()
# for each page....
#jids << ParserWorker.perform_async(page_url)
# end
# crawler finished, parsers may still be running
while parsers_busy?
sleep 5 # wait 5 secs between each check
end
# all parsers complete, trigger notification...
end
def parsers_busy?
status_containers = SidekiqStatus::Container.load_multi(#jids)
for container in status_containers
if container.status == 'waiting' || container.status == 'working'
return true
end
end
return false
end
I've got a small little ruby script that pours over 80,000 or so records.
The processor and memory load involved for each record is smaller than a smurf balls, but it still takes about 8 minutes to walk all the records.
I'd though to use threading, but when I gave it a go, my db ran out of connections. Sure it was when I attempted to connect 200 times, and really I could limit it better than that.. But when I'm pushing this code up to Heroku (where I have 20 connections for all workers to share), I don't want to chance blocking other processes because this one ramped up.
I have thought of refactoring the code so that it conjoins the all the SQL, but that is going to feel really really messy.
So I'm wondering is there a trick to letting the threads share connections? Given I don't expect the connection variable to change during processing, I am actually sort of surprised that the thread fork needs to create a new DB connection.
Well any help would be super cool (just like me).. thanks
SUPER CONTRIVED EXAMPLE
Below is a 100% contrived example. It does display the issue.
I am using ActiveRecord inside a very simple thread. It seems each thread is creating it's own connection to the database. I base that assumption on the warning message that follows.
START_TIME = Time.now
require 'rubygems'
require 'erb'
require "active_record"
#environment = 'development'
#dbconfig = YAML.load(ERB.new(File.read('config/database.yml')).result)
ActiveRecord::Base.establish_connection #dbconfig[#environment]
class Product < ActiveRecord::Base; end
ids = Product.pluck(:id)
p "after pluck #{Time.now.to_f - START_TIME.to_f}"
threads = [];
ids.each do |id|
threads << Thread.new {Product.where(:id => id).update_all(:product_status_id => 99); }
if(threads.size > 4)
threads.each(&:join)
threads = []
p "after thread join #{Time.now.to_f - START_TIME.to_f}"
end
end
p "#{Time.now.to_f - START_TIME.to_f}"
OUTPUT
"after pluck 0.6663269996643066"
DEPRECATION WARNING: Database connections will not be closed automatically, please close your
database connection at the end of the thread by calling `close` on your
connection. For example: ActiveRecord::Base.connection.close
. (called from mon_synchronize at /Users/davidrawk/.rvm/rubies/ruby-1.9.3-p448/lib/ruby/1.9.1/monitor.rb:211)
.....
"after thread join 5.7263710498809814" #THIS HAPPENS AFTER THE FIRST JOIN.
.....
"after thread join 10.743254899978638" #THIS HAPPENS AFTER THE SECOND JOIN
See this gem https://github.com/mperham/connection_pool and answer, a connection pool might be what you need: Why not use shared ActiveRecord connections for Rspec + Selenium?
The other option would be to use https://github.com/eventmachine/eventmachine and run your tasks in EM.defer block in such a way that DB access happens in the callback block (within reactor) in a non-blocking way
Alternatively, and a more robust solution too, go for a light-weight background processing queue such as beanstalkd, see https://www.ruby-toolbox.com/categories/Background_Jobs for more options - this would be my primary recommendation
EDIT,
also, you probably don't have 200 cores, so creating 200+ parallel threads and db connections doesn't really speed up the process (slows it down actually), see if you can find a way to partition your problem into a number of sets equal to your number of cores + 1 and solve the problem this way,
this is probably the simplest solution to your problem