I'm trying to display a number from an api, but I want my page to load faster. So, I'd like to get the number from the api every 5 minutes, and just load that number to my page. This is what I have.
get '/' do
x = Numbersapi.new
#number = x.number
:erb home
end
This works fine, but getting that number from the api takes a while so that means my page takes a while to load. I want to look up that number ahead of time and then every 5 minutes. I've tried using threads and processes, but I can't seem to figure it out. I'm still pretty new to programming.
Here's a pretty simple way to get data in a separate thread. Somewhere outside of the controller action, fire off the async loop:
Data = {}
numbers_api = Numbersapi.new
Thread.new do
Data[:number] = numbers_api.number
sleep 300 # 5 minutes
end
Then in your controller action, you can simply refer to the Data[:number], and you'll get the latest value.
However if you're deploying this you should use a gem like Resque or Sidekiq; it will track failures and is probably optimized more
Related
I'm having some trouble with sending batch requests for the pagespeed API. From what I have seen in my google developers console I should have 100 requests per second with a max of 25,000 per day. However, I'm running into a problem even just trying to do 50 per second. I have tried to impose timing into my ruby application and for some reason that doesn't change the error. I still get the rateLimitExceeded Error from google on a decent amount of the results. I'm doing this on arrays containing ~1000 urls if that matters.
Here's my batch function, I call it in a loop from another function, I thought this might work better for timing. But it didn't seem to change anything.
def send_request(urls)
#psservice.batch do |ps|
urls.each do |url|
ps.run_pagespeed(url) do |result, err|
err.nil? ? #data.push(result) : #errors.push("#{url}, #{err}")
end
end
end
end
This gets called from
#urls.each_slice(50).to_a.each do |url_list|
send_request(url_list, options)
sleep(1)
end
Any ideas why this would occur? Thanks in advance
I misread the quota for Google Pagespeed - it's 100 requests / 100 seconds. So one request a second. It seems the more I check that it actually is 1 request / second. I still have trouble trying to run 100 requests then waiting 100 seconds.
I am working on an application where there are read only screens.
To test whether the data is being fetched on screen load, i want to set some wait time till the screen is ready.
I am using python to record the actions. Is there a way to check the static text on the screen and set the time ?
You can simply use
snooze(time in s).
Example:
snooze(5)
If you want to wait for a certain object, use
waitForObject(":symbolic_name")
Example:
type(waitForObject(":Welcome.Button"), )
The problem is more complicated if your objects are created dynamically. As my app does. In this case, you should create a while function that waits until the object exists. Here, maybe this code helps you:
def whileObjectIsFalse(objectID):
# objectID = be the symbolic name of your object.
counter = 300
objectState = object.exists(objectID)
while objectState == False:
objectState = object.exists(objectID)
snooze(0.1)
counter -= 1
if counter == 0:
return False
snooze(0.2)
In my case, even if I use snooze(), doesn't work all the time, because in some cases i need to wait 5 seconds, in other 8 or just 2. So, presume that your object is not created and tests this for 30 seconds.
If your object is not created until then, then the code exits with False, and you can tests this to stop script execution.
If you're using python, you can use time.sleep() as well
I am working on a eventmachine based application that periodically polls for changes of MongoDB stored documents.
A simplified code snippet could look like:
require 'rubygems'
require 'eventmachine'
require 'em-mongo'
require 'bson'
EM.run {
#db = EM::Mongo::Connection.new('localhost').db('foo_development')
#posts = #db.collection('posts')
#comments = #db.collection('comments')
def handle_changed_posts
EM.next_tick do
cursor = #posts.find(state: 'changed')
resp = cursor.defer_as_a
resp.callback do |documents|
handle_comments documents.map{|h| h["comment_id"]}.map(&:to_s) unless documents.length == 0
end
resp.errback do |err|
raise *err
end
end
end
def handle_comments comment_ids
meta_product_ids.each do |id|
cursor = #comments.find({_id: BSON::ObjectId(id)})
resp = cursor.defer_as_a
resp.callback do |documents|
magic_value = documents.first['weight'].to_i * documents.first['importance'].to_i
end
resp.errback do |err|
raise *err
end
end
end
EM.add_periodic_timer(1) do
puts "alive: #{Time.now.to_i}"
end
EM.add_periodic_timer(5) do
handle_changed_posts
end
}
So every 5 seconds EM iterates over all posts, and selects the changed ones. For each changed post it stores the comment_id in an array. When done that array is passed to a handle_comments which loads every comment and does some calculation.
Now I have some difficulties in understanding:
I know, that this load_posts->load_comments->calculate cycle takes 3 seconds in a Rails console with 20000 posts, so it will not be much faster in EM. I schedule the handle_changed_posts method every 5 seconds which is fine unless the number of posts raises and the calculation takes longer than the 5 seconds after which the same run is scheduled again. In that case I'd have a problem soon. How to avoid that?
I trust em-mongo but I do not trust my EM knowledge. To monitor EM is still running I puts a timestamp every second. This seems to be working fine but gets a bit bumpy every 5 seconds when my calculation runs. Is that a sign, that I block the loop?
Is there any general way to find out if I block the loop?
Should I nice my eventmachine process with -19 to give it top OS prio always?
I have been reluctant to answer here since I've got no mongo experience so far, but considering no one is answering and some of the stuff here is general EM stuff I may be able to help:
schedule next scan on first scan's end (resp.callback and resp.errback in handle_changed_posts seem like good candidates to chain next scan), either with add_timer or with next_tick
probably, try handling your mongo trips more often so they handle smaller chunks of data, any cpu cycle hog inside your reactor would make your reactor loop too busy to accept events such as periodic timer ticks
no simple way, no. One idea would be to measure diff of Time.now to next_tick{Time.now}, do benchmark and then trace possible culprits when the diff crosses a threshold. Simulating slow queries (Simulate slow query in mongodb? ?) and many parallel connections is a good idea
I honestly don't know, I've never encountered people who do that, I expect it depends on other things running on that server
To expand upon bbozo's answer, specifically in relation to your second question, there is no time when you run code that you do not block the loop. In my experience, when we talk about 'non-blocking' code what we really mean is 'code that doesn't block very long'. Typically, these are very short periods of time (less than a millisecond), but they still block while executing.
Further, the only thing next_tick really does is to say 'do this, but not right now'. What you really want to do, as bbozo mentioned, is split up your processing over multiple ticks such that each iteration blocks for as little time as possible.
To use your own benchmarks, if 20,000 records takes about 3 seconds to process, 4,000 records should take about 0.6 seconds. This would be short enough to not usually affect your 1 second heartbeat. You could split it up even farther to reduce the amount of blockage and make the reactor run smoother, but it really depends on how much concurrency you need from the reactor.
I need to regulate how often a Mechanize instance connects with an API (once every 2 seconds, so limit connections to that or more)
So this:
instance.pre_connect_hooks << Proc.new { sleep 2 }
I had thought this would work, and it sort of does BUT now every method in that class sleeps for 2 seconds, as if the mechanize instance is touched and told to hold 2 seconds. I'm going to try a post connect hook, but it is obvious I need something a bit more elaborate, but what I don't know what at this point.
Code is more explanation so if you are interested following along: https://github.com/blueblank/reddit_modbot, otherwise my question concerns how to efficiently and effectively rate limit a Mechanize instance to within a specific time frame specified by an API (where overstepping that limit results in dropped requests and bans). Also, I'm guessing I need to better integrate a mechanize instance to my class as well, any pointers on that appreciated as well.
Pre and post connect hooks are called on every connect, so if there is some redirection it could trigger many times for one request. Try history_added which only gets called once:
instance.history_added = Proc.new {sleep 2}
I use SlowWeb to rate limit calls to a specific URL.
require 'slowweb'
SlowWeb.limit('example.com', 10, 60)
In this case calls to example.com domain are limited to 10 requests every 60 seconds.
Here's what I'm trying to accomplish. Let's say I have 100,000 urls stored in a database and I want to check each of these for http status and store that status. I want to be able to do this concurrently in a fairly small amount of time.
I was wondering what the best way(s) to do this would be. I thought about using some sort of queue with workers/consumers or some sort of evented model, but I don't really have enough experience to know what would work best in this scenario.
Ideas?
Take a look at the very capable Typhoeus and Hydra combo. The two make it very easy to concurrently process multiple URLs.
The "Times" example should get you up and running quickly. In the on_complete block put your code to write your statuses to the DB. You could use a thread to build and maintain the queued requests at a healthy level, or queue a set number, let them all run to completion, then loop for another group. It's up to you.
Paul Dix, the original author, talked about his design goals on his blog.
This is some sample code I wrote to download archived mail lists so I could do local searches. I deliberately removed the URL to keep from subjecting the site to DOS attacks if people start running the code:
#!/usr/bin/env ruby
require 'nokogiri'
require 'addressable/uri'
require 'typhoeus'
BASE_URL = ''
url = Addressable::URI.parse(BASE_URL)
resp = Typhoeus::Request.get(url.to_s)
doc = Nokogiri::HTML(resp.body)
hydra = Typhoeus::Hydra.new(:max_concurrency => 10)
doc.css('a').map{ |n| n['href'] }.select{ |href| href[/\.gz$/] }.each do |gzip|
gzip_url = url.join(gzip)
request = Typhoeus::Request.new(gzip_url.to_s)
request.on_complete do |resp|
gzip_filename = resp.request.url.split('/').last
puts "writing #{gzip_filename}"
File.open("gz/#{gzip_filename}", 'w') do |fo|
fo.write resp.body
end
end
puts "queuing #{ gzip }"
hydra.queue(request)
end
hydra.run
Running the code on my several-year-old MacBook Pro pulled in 76 files totaling 11MB in just under 20 seconds, over wireless to DSL. If you're only doing HEAD requests your throughput will be better. You'll want to mess with the concurrency setting because there is a point where having more concurrent sessions only slow you down and needlessly use resources.
I give it a 8 out of 10; It's got a great beat and I can dance to it.
EDIT:
When checking the remove URLs you can use a HEAD request, or a GET with the If-Modified-Since. They can give you responses you can use to determine the freshness of your URLs.
I haven't done anything multithreaded in Ruby, only in Java, but it seems pretty straightforward: http://www.tutorialspoint.com/ruby/ruby_multithreading.htm
From what you described, you don't need any queue and workers (well, I'm sure you can do it that way too, but I doubt you'll get much benefit). Just partition your urls between several threads, and let each thread do each chunk and update the database with the results. E.g., create 100 threads, and give each thread a range of 1000 database rows to process.
You could even just create 100 separate processes and give them rows as arguments, if you'd rather deal with processes than threads.
To get the URL status, I think you do an HTTP HEAD request, which I guess is http://apidock.com/ruby/Net/HTTP/request_head in ruby.
The work_queue gem is the easiest way to perform tasks asynchronously and concurrently in your application.
wq = WorkQueue.new 10
urls.each do |url|
wq.enqueue_b do
response = Net::HTTP.get_response(uri)
puts response.code
end
end
wq.join