I am trying to integrate some node.js code with my Rails application. Basically its a js file with some code that process will keep running in background.
I have followed the following steps:
Added code in root of rails app in some test_node.js file.
Now what I do is pass a value to my system using exec function of ruby, e.g exec "node test_node.js".
This works perfectly fine but it chop my server from processing any requests.
To pass it to background i tried using nohup e.g: exec "nohup node test_node.js".
When I run this code my server crashes.
I am Rails developer and never worked on node app so have no idea if I taking it right way or not.
exec replaces the currently running process with a new one. Thus, to run something in the background you should fork and exec in the child.
fork { exec('node', 'test_node.js', ...) }
nohup is not needed.
See also Ruby, Difference between exec, system and %x() or Backticks
Related
I want to start a process from inside a controller.
I've tried the usual
pid = fork do
code
end
Process.detach(pid)
But nothing is happening. When I try with eval(code) in the fork block the code runs but it's the actual rails server/puma running it. This means that when I kill the process I also shut down the whole server.
I had some code before that I lost that worked and I'm nearly sure it used exec or eval or something like this that created a process(and therefore returned a pid to be able to kill it later) and I remember checking with ps that it was run by something of rails but not the actual whole server.
Why isn't the fork do block enough for it to work? What's the way to do it?
And, for non-testing purposes and actual implementation, how can I make it run totally independent from the rails server?
You can execute a shell command from inside your Rails controller using exec.
I hope you are looking for the same. The process you start on the system will be totally independent of the Rails server and will be visible under ps command if it is running when you hit the command.
Documentation: http://ruby-doc.org/core-2.5.1/Kernel.html#method-i-exec
I have a simple shell script (happy.sh) that I am currently running by hand (. ./happy.sh) every time I restart a rails server. It sets some environment variables that I need because of various APIs I'm using. However, I was wondering if there's some way of having rails run the script itself whenever I run "guard" or "rails s"
Thanks
If you use foreman, you can define all processes you needed started on application start into a Procfile. (including bbundle exec rails server -p $PORT)
By calling foreman start, all the process starts up.
More information can be gotten here on this cast
Proper way of setting ENV variables is putting them in bash_proflle or bashrc depending of linux distro.
vi ~/.bash_proflle
And then add something like
export MY_RAILS_VAR=123
Then you don't need to run any ENV initialization scripts on rails start.
With my large application, the Rails console takes a while to load up. Is there a way to single commands more easily?
I'd also like to be able to automate stuff, and echo "query" | rails console isn't a great way to do things.
Thoughts?
EDIT: What about a long-running process that I can ping queries to whenever I have need?
There are two main ways to run commands outside console:
Rake task which depends on :environment
rails runner (previously script/runner), eg:
$ rails runner "query"
Both are pretty well documented on the rails guide: https://guides.rubyonrails.org/command_line.html#bin-rails-runner
Both of these methods will still take the same time as a console to fire up, but they are useful for non-interactive tasks.
Just pipe it in:
echo 'puts Article.count' | bundle exec rails c
It should now be a lot faster than when then the question was originally asked, because of Spring. It's not immediate, but still a lot faster than spinning up the whole app. Use this for the fast lane, it should run in under a second (assuming your required command is fast):
echo 'puts Article.count' | spring rails c
If you really want a single long-running process, you could easily do it by creating a controller action that simply runs whatever you POST to it, then send commands to it using curl behind an alias. The action would of course be completely insecure and should be triple-guarded against running anywhere near production, but it would be easy to setup.
Solution: bundle exec command allows us to run an executable script in the specific context of the project's bundle - making all gems specified in the Gemfile available to require in Ruby application. In addition it eventually avoids any conflicts with other versions of rake installed globally.
echo '<command>' | bundle exec rails c
for more information look at the documentation of bundler
example:
configuration_item=$(echo 'ConfigurationManager.getKey("authentication_method")' | bundle exec rails c )
echo $configuration_item
#output:
MFA_authentication
I finally got the DelayedJobs plugin working for Rails 2, and it does indeed work fine...as long as I run:
rake jobs:work
Just like the readme says, to be fair.
BUT, this doesn't fit my requirements...what kind of background task requires you to have a shell open, and a command running? That'd be like having to say script/server to run my rails app, and never getting that -d option so it'll keep running even after I close my shell.
Is there ANY way to keep the workers getting processed in the backgroun, or in daemon mode, or whatever?
I had a ray of hope when I saw the
You can also run by writing a simple
#script/job_runner#, and invoking it
externally:
Line in the readme...but...that just does the exact same thing the rake task does, you just call it a different way.
What I want:
I want to start my rails app, then start whatever will process the workers, and have BOTH of them run invisibly in the background, without the need for me to babysit it and keep the shell that started it running.
(My server is something I SSH into, so I don't want to have that shell that SSHed into it running 24/7 (especially since I like to turn off my local computer now and again)).
Is there any way to acomplish this?
You can make any *nix command run on the background by appending an & to its end:
rake jobs:work &
Just make sure you exit the shell (or use the disown command) to detach the process from your login session... Otherwise, if your session disconnects, the processes you own will be killed with it.
Perhaps Beanstalkd and Stalker?
Beanstalk is a fast and easy way to queue background tasks. Stalker provides a nice wrapper interface for creating these jobs.
See the railscast on it for more information
Edit:
You could also run that rake task as a cronjob which would mean the server would run it periodically without you needing to be logged in
Use the collectiveidea fork of delayed_job... It's more actively developed and has support for running the jobs in a daemon without any extra messing about.
My capistrano script calls
RAILS_ENV=production script/delayed_job start
I have a daemon that should run behind my rails app doing db modifications.I implemented that daemon using ruby daemons gem. I want to start that daemon at the start of my app. Whenever my app starts, I need to start that daemon.
How can I do this..?
If you must start it during Rails initialization:
Create a ruby file that will start the daemon. Say invoke_daemon.rb
Put this file in config/initializers/invoke_daemon.rb
However if it isn't mandatory, I would suggest creating a binary executable or a rake task and manually starting it through command line. This way it runs as a separate process. You can simply add it to your deployment scripts for production boxes and on development box run it manually. A few examples would be searchd, the search daemon for sphinx and thinking_sphinx:delayed_delta rake task from thinking_sphinx.
For your knowledge you have to take look of
Rails Life cycle
I have just implemented this thing. I have implemented on Windows7.
I have created one batch file let's say my_batch.bat, which contains ruby command i.e. ruby my_daemon.rb file.
In addition, to execute this file when my app starts , I have just added one statement in environment.rb file which executes that batch file. i.e. system ("my_batch.bat").
But I am not sure that this is a good way to implement this task.