Thread and websocket

[Jean-eric Godard]

Hello,

I'm trying to build a home monitoring system using roda.

I need to monitor a file on my server: when a file is modify I'd like to send a message using a websocket.

I try to implement a solution using the filewatcher gem, as shown below

plugin "faye/websocket", adapter: :thin, ping: 45

route do |r|

if Faye::WebSocket.websocket?(env)

ws = Faye::WebSocket.new(env)

ws.on :message do |event|

client_data = event.data

if client_data.is_json?

 data = JSON.parse(client_data)  

t=Thread.new do

Filewatcher.new(data[:file]).watch do |changes|

ws.send(data[:file]

end

t.join

...

The problem is that the roda doesnt respond anymore.

I imagine this is not the way to implement threads with Roda but didn't find how to proceed.

If someone can help me or teach me how to use threads whithin Roda I'll be very gratefull.

Thanks

Jean-Eric

[Jeremy Evans]

Thin is an event driven webserver, and probably doesn't work well with creating and joining thread at runtime. For what it's worth, I'm not sure what the point of creating a thread just to join it immediately in this case.

Since it sounds like you only need unidirectional communication and not bidirectional communication, you are probably better off using something like message_bus as opposed to websockets.  The roda-message_bus gem provides message_bus integration for Roda.  If you really want to use websockets, you could try the websockets plugin (https://github.com/jeremyevans/roda/blob/2.28.0/lib/roda/plugins/websockets.rb).  It was removed in Roda 3 mostly because it made the tests take much longer and not be as reliable, but should still work fine.  You could just copy and paste the plugin code into your application.

Thanks,

Jeremy

[Luke Stutters]

Dear Jean-Marc,

I am not sure why you want to keep watching these files. Files are not doing anything suspicious, it is the processes that are up to no good. But I know you have a file problem so this might help.

I have been developing something similar using Roda Server Sent Events because I do not like the web sockets. In fact, some of them are very suspicious. I could make a socket but I prefer not to.

The code that watches the suspicious file looks like this:

#!/usr/bin/ruby

# File watcher using Roda and SSE

require 'roda'

require 'filewatcher'

# Use an array of ruby queues to keep track of the connections

# Global variable is best variable

QUEUES = []

class App < Roda

  plugin :streaming # Makes the SSE work

  route do |r|

    # "Upgrade" the connection to an SSE

    response['Content-Type'] = 'text/event-stream'

    response['X-Accel-Buffering'] = 'no' # for nginx (boooooo)

    # Add the connection to the queue array

    q = Queue.new

    QUEUES << q

    stream(loop: true, async: true, callback: proc { QUEUES.delete(q) }) do |out|

      out << "data: #{q.pop}\n\n"

    end

  end

end

# Update all connections in a single thread

Thread.new do

  Filewatcher.new('my_suspicious_file.txt').watch do |changes|

    # Newlines break SSEs, need to do stuff like this:

    puts changes.inspect

    update = changes.gsub(/[\r\n]/, "\ndata: ")

    # Send the update to each SSE connection

    QUEUES.each do |q|

      q.push update

    end

  end

end

# Listen everywherrr

Rack::Handler.default.run(App, Hostname: '0.0.0.0', Port: 8080)

Then I can listen for file changes using this in ruby:

#!/usr/bin/ruby

# Listen for file eventz

require 'ld-eventsource'

sse_client = SSE::Client.new("http://localhost:8080") do |client|

  client.on_event do |event|

    puts "I received an event of type #{event.type}: #{event.data}"

  end

end

while true

  sleep 1

end

If you are a java script:

var evtSource = new EventSource("http://localhost:8080");

evtSource.onmessage = function(event) { console.log(event) }

You will have to install gems, you could use bundler but it makes me confused:

sudo gem install roda filewatcher ld-eventsource

It is not really what you asked for but I enjoyed making it.

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[Jean-Eric Godard]

Thanks Jeremy and Luke for your answers. 

To explain a bit more I’m building an open source cross platform frameworks based on Cordova Ruby and opal that can create applications, be booted and used as gui for FreeBSD  but  also has web mode. 

I chose to test the framework with two use cases : home automation and code learning,/machine scripting.

Both use case imply needs to use background  tasks. 

In the first use case I need to monitor various analog inputs and send a message to connected user when a value is reach. ( ex monitoring température ) so Ruby needs to check inputs every second and refresh the connected user browsers. 

In the second case user create script and when user save it user that subscribe the to the script have their background task refreshed ( ex : a new algorithm for home automation)

Anyway I’ll try both solutions,  maybe roda-message_bus could partially solve the problem. 

Jeremy you talk about websocket plugins isn’t it the one I already used I am a bit confused. 

Luke I’ll examine your answer it’ll take make a bit of time to understand and use it but it maybe an interesting way. 

The frameworks is also used to create websites, interactive video, video games, animations,  and much more..using Ruby. 

The state and code quality of the  project is closer to a proof of concept than a production ready solution for now. 

I’m not an expert programmer’ I just have the will to make it real!

If you are curious here is the link : https://github.com/atomecorp/atome

Thanks for your precious help. 

Cheers 

Jean-Eric 

[Jean-eric Godard]

hi again, 

Luke, after analyzing your solution I succeed to adapt to monitor analog inputs and files change in a separate thread and push the result using websockets,and it works perfectly!! 

Thanks a lot to you all!

Jean-Eric