Is there a way to assign a custom name to a process started using the command below
~lein run
The process stared by the above command is as displayed below -
~lsof -i tcp:8082
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
java 96029 <username> 89u IPv6 0xa04954e1ea972891 0t0 TCP *:us-cli (LISTEN)
It's possible though it gets a bit ugly and likely not worth the trouble
You would need to make a symlink to java with an alternate name, and modify lein to call that instead of calling java. You could do this by writing a lein plugin for instance. When Linux starts a process the name of the process it uses the name of the file from which the process was run as the name of the process thereafter, so you need to change the name of the file that gets run to create the process that will open the port, in this case "java".
If all you needed was an easy way to find either the process that opened the port or it's parent process then you could just make a script with a good name that called lein run. This would show up in the output from ps though not from lsof.
Related
Is it possible to write a bash script that opens a remote node (i.e. through ssh and/or slurm) and starts an interactive session there after running some commands? I'm trying to automate the process of starting a jupyter session on a remote computing cluster, which currently looks like this:
ssh into a login node of the remote cluster, using a specific port
use slurm to request an interactive session on one of the compute nodes, including x11 forwarding through that port
change directory to the working directory
activate conda environment for my project
open jupyter from the command line, specifying the port I used previously
It's a lengthy process, and if I get something wrong at any step I usually have to go back and start from the beginning because the port I'm using is still tied up. So I'm looking for a way I can run a single script (possibly with arguments) from my local machine that jumps through all the hoops to get me a working jupyter session with a link I can paste to my browser.
Like #Diego Torres Milano said, you would need to write a script locally that could do the interactive part, then invoke that via a remote script.
But since your process is interactive, this gets tricky. Luckily, linux has a tool which can easily be installed via a package manager called expect which has the ability to write logic to execute multi-step interactive scripts.
So you would write an expect script which would "expect" certain prompts, then it can read those prompts and use conditional logic respond to those prompts appropriately.
Once you have this written and it works locally, it's just a matter of executing it via ssh from a remote server as:
ssh user#12.34.56.78 /path/to/script.ex
I've written a TCP Server in ruby running on port 2000 with event machine.
Right now, what I do is ssh to my server and run the command ruby lib/tcp_server.rb to turn on the server, but it shuts down when I log out.
I've tried nohup and using & but nothing seems to stick for the server for a long time.
So my question is, how do I deploy this server on port 2000 and keep it running, like how we deploy Rails to nginx.
It's not a webserver, but an a tcp server for a connected device, if that helps.
Thanks!
Solution 1: tmux or screen
This is the simplest way to approach, you will have to create a tmux or screen session, then start your server in that session.
Solution 2: nohup
nohup ruby lib/tcp_server.rb > stdout.log 2> stderr.log &
You've tried nohup and using &, I suppose you've already known how to do.
Solution 3: daemonize
You can detach from the shell and daemonize the process by forking
it twice, setting the session ID and changing the current working directory.
def daemonize
exit if fork
Process.setsid
exit if fork
Dir.chdir '/'
end
With this approach, you will have to redirect stdout and stderr to keep logs.
Another way to daemonize is to use gems like daemons.
update:
To restart the process automatically after being killed, you need a process manager like god or pm2.
To start the process automatically after booting, you need to compose an init scripts but how it looks like depends on your service management system and operating system. One of the most well-known is System V. If you are using Ubuntu, you might want to take a look at Upstart or systemd.
I noticed that if I set another port number instead of the default one in derby (1527) in the derby.properties with for instance:
derby.drda.portNumber=1528
It will then correctly start up the server on that new port but unfortunately when calling stop script it will still attempt to kill something on the default port and leaving the derby alive. Is that a bug or is there something else that needs to be addressed in the properties file to make it work?
You are probably looking for the -p portnumber argument to stopNetworkServer: http://db.apache.org/derby/docs/10.13/adminguide/tadminconfigshuttingdownthenetworkserver.html
I am trying to do some work on a remote machine and disconnect without terminating the work. I have tried both nohup and screen, unfortunately it is not working out. After I type exit to logout my work also terminates immediately.
I am trying to run 108 simulations on a remote machine. For that purpose I have written a script named batch.sh which runs one simulation after the other until all 108 are done. The program that actually runs a simulation launches 5 programs in 5 different terminals (using xterm -e). I run batch.sh using:
nohup bash batch.sh &
As long as I am connected everything works just fine. If I disconnect and then reconnect to check whether everything is working as it should...no joy :(
Are there any caveats I am overlooking? Possibly because my program launches other programs in external terminals?
UPDATE
If I use the suggestions of adding -oForwardX11=no to ssh and unset DISPLAY before launching my script I get these errors:
nohup: ignoring input and appending output to nohup.out
In nohup.out I have these messages:
xterm Xt error: Can't open display:
xterm: DISPLAY is not set
Apparently your script/program is trying to launch xterm on its own. These days many systems enable X11 forwarding for their SSH client by default - as a result the DISPLAY variable is set in your shell session but becomes invalid once you disconnect. Therefore, as long as you are connected to the remote system, the xterm processes can access the X server on your local machine through the SSH connection, but die once that connection is severed.
I have occasionally encountered the same issue with Java programs that use e.g. the Java AWT subsystem to generate image files, even when there is no actual graphical window. You should first see if your program will somehow adapt if there is no X server available. One option is to disable X11 forwarding with the -oForwardX11=no option to ssh:
$ ssh -oForwardX11=no user#server.host.name
You could also try unsetting the DISPLAY environment variable before starting your script and see what happens.
However, if your program is launching xterm windows indiscriminately then you'd have to make it e.g. use an output file on the server instead - by modifying it, if necessary. As an added advantage, you would get rid off the network load and timing overhead involved with forwarded X connections.
If you cannot change the way your program works and you do not actually care about the output in those xterm windows, then you could try launching a virtual framebuffer X server on the remote system and have your script use that for xterm.
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.