For some time I have been using an old Ruby distribution (I think it was 1.8.6) on which I coded with the socket library. The old library had a method called ready?, which checked whether there was still data to be received without blocking. What would be the best replacement for that in 1.9?
The reason why I require it is as I have a program structured like this:
def handle_socket_messages
while true
break unless messages_to_send
sent_messages
end
while #s and #s.ready?
#read messages
readStr = #s.recv(0x1024)
...
end
end
(I then have another loop which keeps executing the handle_socket_messages method and then uses a sleep, so that the loop doesn't spin too fast, along with some other methods.
As you can see, I need to check whether I will receive data using #s.ready? (#s is a socket), otherwise the loops hang at readStr = #s.recv(0x1024), where the socket keeps wanting to receive data which the server doesn't send (It's waiting for data when it shouldn't).
What would be the best replacement for this method?
The solution was:
class Socket
def ready
not IO.select([self], nil, nil, 0) == nil
end
end
I've been using the ready? method successfully in Ruby 2.2.2 by requiring io/wait. There is a bit more info in this SO answer: https://stackoverflow.com/a/3983850/2464
Related
Sorry for such a big question. I do not have much experience with Rails threads and mutex.
I have a class as follow which is used by different controllers to get the license for each customers.
Customers and their licenses gets added and removed every hour. An api is available to get all customers and their licenses.
I plan to create a rake task to call update_set_customers_licenses, run hourly via a cronjob.
I have following questions:
1) Even with a mutex, currently there is a potential for problem, there is a chance that my rake task can occur while updating. Any idea on how to solve this?
2) My design below writes the json out to a file, this is done is for safety as the api is not that reliable. As can be seen, it is not reading the file back, so in essence the file write is useless. I tried to implement a file read but together with mutex and rake task, it gets really confusing. Any pointers will help here.
class Customer
##customers_to_licenses_hash = nil
##last_updated_at = nil
##mutex = Mutex.new
CUSTOMERS_LICENSES_FILE = "#{Rails.root}/tmp/customers_licenses"
def self.cached_license_with_customer(customer)
Rails.cache.fetch('customer') {self.license_with_customer(customer)}
end
def self.license_with_customer(customer)
##mutex.synchronize do
license = ##customers_to_licenses_hash[customer]
if license
return license
elsif(##customers_to_licenses_hash.nil? || Time.now.utc - ##last_updated_at > 1.hours)
updated = self.update_set_customers_licenses
return ##customers_to_licenses_hash[customer] if updated
else
return nil
end
end
end
def self.update_set_customers_licenses
updated = nil
file_write = File.open(CUSTOMERS_LICENSES_FILE, 'w')
results = self.get_active_customers_licenses
if results
##customers_to_licenses_hash = results
file_write.print(results.to_json)
##last_updated_at = Time.now.utc
updated = true
end
file_write.close
updated
end
def self.get_active_customers_licenses
#http get thru api
#return hash of records
end
end
I'm pretty it's the case that every time rails loads, the environment is "fresh" and has no concept of "state" in between instances. That is to say, a mutex in one ruby instance (the one request to rails) has no effect on a second ruby instance (another request to rails or in this case, a rake task).
If you follow the data upstream, you'll find that the common root of every instance that can be used to synchronize them is the database. You could use transactional blocks or maybe a manual flag you set and unset in the database.
I am trying to interact with Matlab.Application.Single win32ole objects in my rails application. The problem I am running into is that while I am developing my application, each separate request reloads my win32ole objects so I loose the connection to my matlab orignal instances and new instances are made. Is there a way to persist live objects between requests in rails? or is there a way to reconnect to my Matlab.Application.Single instances?
In production mode I use module variables to store my connection between requests, but in development mode Module variables are reloaded every request.
here is a snippet of my code
require 'win32ole'
module Calculator
#engine2 = nil
#engine3 = nil
def self.engine2
if #engine2.nil?
#engine2 = WIN32OLE.new("Matlab.Application.Single")
#engine2.execute("run('setup_path.m')")
end
#engine2
end
def self.engine3
if #engine3.nil?
#engine3 = WIN32OLE.new("Matlab.Application.Single")
#engine3.execute("run('setup_path.m')")
end
#engine3
end
def self.load_CT_image(file)
Calculator.engine2.execute("spm_image('Init','#{file}')")
end
def self.load_MR_image(file)
Calculator.engine3.execute("spm_image('Init','#{file}')")
end
end
I am then able to use my code in my controllers like this:
Calculator.load_CT_image('Post_Incident_CT.hdr')
Calculator.load_MR_image('Post_Incident_MRI.hdr')
You can keep an app-wide object in a constant that won't be reset for every request. Add this to a new file in config/initializers/:
ENGINE_2 = WIN32OLE.new("Matlab.Application.Single")
You might also need to include the .execute("run('setup_path.m')") line here as well (I'm not familiar with WIN32OLE). You can then assign that object to your instance variables in your Calculator module (just replace the WIN32OLE.new("Matlab.Application.Single") call with ENGINE_2, or simply refer to them directly.
I know this is beyond the scope of your question, but you have a lot of duplicated code here, and you might want to think about creating a class or module to manage your Matlab instances -- spinning up new ones as needed, and shutting down old ones that are no longer in use.
I'm not sure how to solve this big performance issue of my application. I'm using open-uri to request the most popular videos from youtube and when I ran perftools https://github.com/tmm1/perftools.rb
It shows that the biggest performance issue is Timeout.timeout. Can anyone suggest me how to solve the problem?
I'm using ruby 1.8.7.
Edit:
This is the output from my profiler
https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B4bANr--YcONZDRlMmFhZjQtYzIyOS00YjZjLWFlMGUtMTQyNzU5ZmYzZTU4&hl=en_US
Timeout is wrapping the function that is actually doing the work to ensure that if the server fails to respond within a certain time, the code will raise an error and stop execution.
I suspect that what you are seeing is that the server is taking some time to respond. You should look at caching the response in some way.
For instance, using memcached (pseudocode)
require 'dalli'
require 'open-uri'
DALLI = Dalli.client.new
class PopularVideos
def self.get
result = []
unless result = DALLI.get("videos_#{Date.today.to_s}")
doc = open("http://youtube/url")
result = parse_videos(doc) # parse the doc somehow
DALLI.set("videos_#{Date.today.to_s}", result)
end
result
end
end
PopularVideos.get # calls your expensive parsing script once
PopularVideos.get # gets the result from memcached for the rest of the day
I've crafted a basic TCP client using EventMachine. Code:
# run.rb
EventMachine::run do
EventMachine::connect $config_host, $config_port, Bot
end
# bot.rb
module Bot
def post_init
# log us in and do any other spinup.
sleep(1)
send_data $config_login + "\n"
EventMachine.add_periodic_timer($config_keepalive_duration) { send_data $config_keepalive_str + "\n" }
#valid_command = /^<#{$config_passphrase}:([^>:]+):(#\d+)>(.*)$/
end
def receive_data(data)
if(ma = #valid_command.match(data))
command, user, args = ma[1,3]
args.strip!
command.downcase!
p "Received: #{command}, #{user}, #{args}"
# and.. here we handle the command.
end
end
end
This all works quite well. The basic idea is that it should connect, listen for specially formatted commands, and execute the command; in executing the command, there may be any number of "actions" taken that result in various data sent by the client.
But, for my next trick, I need to add the ability to actually handle the commands that Bot receives.
I'd like to do this using a dynamic library of event listeners, or something similar to that; ie, I have an arbitrary number of plugins that can register to listen for a specific command and get a callback from bot.rb. (Eventually, I'd like to be able to reload these plugins without restarting the bot, too.)
I've looked at the ruby_events gem and I think this makes sense but I'm having a little trouble of figuring out the best way to architect things. My questions include...
I'm a little puzzled where to attach ruby_events listeners to - it just extends Object so it doesn't make it obvious how to implement it.
Bot is a module, so I can't just call Bot.send_data from one of the plugins to send data - how can I interact with the EM connection from one of the plugins?
I'm completely open to any architectural revisions or suggestions of other gems that make what I'm trying to do easier, too.
I'm not sure exactly what you're trying to do, but one common pattern of doing this in EM is to define the command handlers as callbacks. So then the command logic can be pushed up out of the Bot module itself, which just handles the basic socket communication and command parsing. Think of how a web server dispatches to an application - the web server doesn't do the work, it just dispatches.
For example something like this
EM::run do
bot = EM::connect $config_host, $config_port, Bot
bot.on_command_1 do |user, *args|
# handle command_1 in a block
end
# or if you want to modularize it, something like this
# where Command2Handler = lambda {|user, *args| #... }
bot.on_command_2(&Command2Handler)
end
So then you just need to implement #on_command_1, #on_command_2, etc. in your Bot, which is just a matter of storing the procs to instance vars; then calling them once you parse the passed commands out of your receive_data.
A good, very readable example of this in production is TwitterStream.
I have some ruby code (1.9) like
#rd,#wd = IO.pipe
def callback()
puts #wd.class
# do stuff
end
pid = fork do
#rd.close
register_callback(:callback)
end
#wd.close
# do some stuff in parent process
register_callback is a C extension that makes a blocking system call, and upon certain conditions will call the ruby function associated with the symbol passed in.
However, #wd is of type NilClass according to the message I get when I run this program and it tries to access #wd in the callback function, which doesn't make any sense to me. Any help is appreciated.
after you call the register_callback method. The rest of the code continues to execute (as you do the register_callback method call inside fork). So #wd.close runs, before your callback is made. Hence when the callback() method is finally called. #wd is nil (which is the result of #wd.close).