I have these rake tasks that will occasionally fail. I want to use monit to monitor them and to restart them if necessary.
I have read the other ruby/monit threads on StackOverflow. My case is different in that these programs require my Rails environment in order to work. That's why I have them as rake tasks now.
Here is one of the tasks I need to monitor, in it's entirety:
task(process_updates: :environment) do
`echo "#{Process.pid}" > #{Rails.root}/log/process_alerts.pid`
`echo "#{Process.ppid}" > #{Rails.root}/log/process_alerts.ppid`
SynchronizationService::process_alerts
end
My question is, do I leave this as a rake task, since SynchronizationService::process_alerts requires the Rails environment to work? Or is there some other wrapper I should invoke and then just run some *.rb file?
Monit can check for running pid, since you're creating pid when you run task you can create a monit config which should look something like this:
check process alerts with pidfile RAILSROOT/log/process_alerts.pid
start program = "cd PATH_TO_APP; rake YOURTASK" with timeout 120 seconds
alert your#mail.com on { nonexist, timeout }
Of course RAILSROOT, PATH_TO_APP, YOURTASK should correspond to your paths/rake task.
Monit then will check for running process in system using the pidfile value and will start the process using start program command if it can't find running process.
Related
I have a rake task :
task :kill_process do
system %q(ps -ef | awk '{if($8~"java" || $8~"glassfish" || $8~"ruby" || $8~"god" || $8~"couch"){printf("Killing : %s \n",$2);{system("kill -9 "$2)};}}')
end
This is basically killing processes. And this task is a part of another rake task :
desc "stop the entire system"
task :stop => [...., :kill_process]
There's another task:
desc "start the entire system"
task :start => [....]
When I am doing rake stop && rake start
stop task is executed successfully. but rake start is not executing.
If i execute both tasks separately, then it works fine. but not in rake stop && rake start
What will be better to use here exec function or system or any other, please suggest me.
My only requirement is to kill these mentioned processes at the end of rake stop. But also it should not effect other things like rake stop && rake start should work fine.
As mentioned in the comments, the exit code is 137 which evaluates to false and therefore the other part of the && does not get executed. The reason for this is probably kill -9.
There are a few options now.
Return 0 from your rake task, something like exit(0)
Don't use kill -9
Create restart command which does execute stop and start but without logically depending on each other (&&).
Exit code 137 indicates that a process has received a SIGKILL signal and was thus killed from the outside.
This happens since a Rake task is also executed by Ruby. As such, your stop task is sending a SIGKILL to its own process too (along with all other Ruby processes on the system). Now, since you have specified that you only want to execute the rake start process if the previous process was successful (i.e. had a exit code of 0), your shell doesn't start the rake task.
To quickly fix this, you can instead run rake stop; rake start, i.e run the two processes regardless of their individual exit codes (by default).
However, a better idea would probably to make your stop task more explicit and only kill the specific processes you need rather than everything in sight which looks slightly like a related process. This will likely result in a more stable system overall too when you don't kill potentially unrelated processes all the time.
Based on an external redis queue, I want a Sinatra application to run a script like this:
ruby fetch_vin.rb vin_number_123
This will fire up watir-webdriver and report to the queue appropriately. When the script is finished, everything but the Sinatra app should close.
It seems however that Thread, as well as exec and spawn are all blocking when ran from inside ruby.
How do I fire & forget?
You can use Process#spawn:
pid = Process.spawn("ruby fetch_vin.rb vin_number_123")
Process.detach(pid)
I think the bit you were missing was calling detach after the process was spawned. This will detach and let both processes continue to run. Will work for any command, not just a ruby script.
See Process Ruby Docs for more details.
How do I launch a thread within a rake task then kill the tread when the task is complete.
Essentially I am writing a rake task to test a jekyll site. I would like be able to launch the server, do some other tasks and then destroy the thread when the task is complete. Here is what I have thus far:
task :test_site do
`ejekyll --server`
`git -Xdn`
if agree( "Clean all ignored files?")
git -Xdf
end
end
but unfortunately the only way I know of to stop the jekyll --server is to use ctrl c. I would be happy to hear of a way to stop a jekyll --server in a manor which does not exit the rake task but please just comment as the question is specifically asking about threading and rake tasks.
You want Process.spawn, not a thread. It's a new process, not a thread of execution within an existing process. You get the PID back, so just send Process.kill(:QUIT, pid) or whatever method you want to use to kill the spawned processed.
pid = Process.spawn(
"ejekyll", "--server",
out: "/dev/null",
err: "/dev/null"
)
# you may need to add a short sleep() here
# other stuff
Process.kill(:QUIT, pid) && Process.wait
If ejekyll has a command line option to run in the foreground, it would be better to use that, otherwise if it self-daemonizes you need to know where it stores its PID file, in order to identify and kill the daemon.
I have a master-workers architecture where the number of workers is growing on a weekly basis. I can no longer be expected to ssh or remote console into each machine to kill the worker, do a source control sync, and restart. I would like to be able to have the master place a message out on the network that tells each machine to sync and restart.
That's where I hit a roadblock. If I were using any sane platform, I could just do:
exec('ruby', __FILE__)
...and be done. However, I did the following test:
p Process.pid
sleep 1
exec('ruby', __FILE__)
...and on Windows, I get one ruby instance for each call to exec. None of them die until I hit ^C on the window in question. On every platform I tried this on, it is executing the new version of the file each time, which I have verified this by making simple edits to the test script while the test marched along.
The reason I'm printing the pid is to double-check the behavior I'm seeing. On windows, I am getting a different pid with each execution - which I would expect, considering that I am seeing a new process in the task manager for each run. The mac is behaving correctly: the pid is the same for every system call and I have verified with dtrace that each run is trigging a call to the execve syscall.
So, in short, is there a way to get a windows ruby script to restart its execution so it will be running any code - including itself - that has changed during its execution? Please note that this is not a rails application, though it does use activerecord.
After trying a number of solutions (including the one submitted by Byron Whitlock, which ultimately put me onto the path to a satisfactory end) I settled upon:
IO.popen("start cmd /C ruby.exe #{$0} #{ARGV.join(' ')}")
sleep 5
I found that if I didn't sleep at all after the popen, and just exited, the spawn would frequently (>50% of the time) fail. This is not cross-platform obviously, so in order to have the same behavior on the mac:
IO.popen("xterm -e \"ruby blah blah blah\"&")
The classic way to restart a program is to write another one that does it for you. so you spawn a process to restart.exe <args>, then die or exit; restart.exe waits until the calling script is no longer running, then starts the script again.
I'm writing a ruby bootstrapping script for a school project, and part of this bootstrapping process is to start a couple of background processes (which are written and function properly). What I'd like to do is something along the lines of:
`/path/to/daemon1 &`
`/path/to/daemon2 &`
`/path/to/daemon3 &`
However, that blocks on the first call to execute daemon1. I've seen references to a Process.spawn method, but that seems to be a 1.9+ feature, and I'm limited to Ruby 1.8.
I've also tried to execute these daemons from different threads, but I'd like my bootstrap script to be able to exit.
So how can I start these background processes so that my bootstrap script doesn't block and can exit (but still have the daemons running in the background)?
As long as you are working on a POSIX OS you can use fork and exec.
fork = Create a subprocess
exec = Replace current process with another process
You then need to inform that your main-process is not interested in the created subprocesses via Process.detach.
job1 = fork do
exec "/path/to/daemon01"
end
Process.detach(job1)
...
better way to pseudo-deamonize:
`((/path/to/deamon1 &)&)`
will drop the process into it's own shell.
best way to actually daemonize:
`service daemon1 start`
and make sure the server/user has permission to start the actual daemon. check out 'deamonize' tool for linux to set up your deamon.