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A cron job for rails: best practices?

What's the best way to run scheduled tasks in a Rails environment? Script/runner? Rake?

Node.js as a background service

Since this post has gotten a lot of attention over the years, I've listed the top solutions per platform at the bottom of this post.

Original post:

I want my Node.js server to run in the background, i.e.: when I close my terminal I want my server to keep running. I've googled this and came up with this tutorial, however it doesn't work as intended. So instead of using that daemon script, I thought I just used the output redirection (the 2>&1 >> file part), but this too does not exit - I get a blank line in my terminal, like it's waiting for output/errors.

I've also tried to put the process in the background, but as soon as I close my terminal the process is killed as well.

So how can I leave it running when I shut down my local computer?

Top solutions:

• Systemd (Linux)
• Launchd (Mac)
• node-windows (Windows)
• PM2 (Node.js)

Logging in Linux

So I have a daemon running on a linux system, and I want to have a record of its activities: a log. The question is, what is the "best" way to accomplish this?

My first idea is to simply open a file and write to it.

FILE* log = fopen("logfile.log", "w");
/* daemon works...needs to write to log */
fprintf(log, "foo%s\n", (char*)bar);
/* ...all done, close the file */
fclose(log);

Is there anything inherently wrong with logging this way? Is there a better way, such as some framework built into linux?

How can I run a Perl script as a system daemon in linux?

What's a simple way to get a Perl script to run as a daemon in linux?

Currently, this is on CentOS. I'd want it to start up with the system and shutdown with the system, so some /etc/rc.d/init.d integration would also be nice, but I could always add a custom line to /etc/rc.d/rc.local.

How do you create a daemon in Python?

Searching on Google reveals x2 code snippets. The first result is to this code recipe which has a lot of documentation and explanation, along with some useful discussion underneath.

However, another code sample, whilst not containing so much documentation, includes sample code for passing commands such as start, stop and restart. It also creates a PID file which can be handy for checking if the daemon is already running etc.

These samples both explain how to create the daemon. Are there any additional things that need to be considered? Is one sample better than the other, and why?

How do I run a Node.js application as its own process?

What is the best way to deploy Node.js?

I have a Dreamhost VPS (that's what they call a VM), and I have been able to install Node.js and set up a proxy. This works great as long as I keep the SSH connection that I started node with open.

How to start a background process in Python?

I'm trying to port a shell script to the much more readable python version. The original shell script starts several processes (utilities, monitors, etc.) in the background with "&". How can I achieve the same effect in python? I'd like these processes not to die when the python scripts complete. I am sure it's related to the concept of a daemon somehow, but I couldn't find how to do this easily.

Run php script as daemon process

I need to run a php script as daemon process (wait for instructions and do stuff). cron job will not do it for me because actions need to be taken as soon as instruction arrives. I know PHP is not really the best option for daemon processes due to memory management issues, but due to various reasons I have to use PHP in this case. I came across a tool by libslack called Daemon (http://libslack.org/daemon) it seems to help me manage daemon processes, but there hasn't been any updates in the last 5 years, so I wonder if you know some other alternatives suitable for my case. Any information will be really appreciated.

How to Daemonize a Java Program?

I have a Java program that I'd like to daemonize on a linux system. In other words, I want to start running it in a shell and have it continue running after I've logged out. I also want to be able to stop the program cleanly.

I found this article which uses a combination of shell scripting and Java code to do the trick. It looks good, but I'd like something simpler, if possible.

What's your preferred method to daemonize a Java program on a Linux system?

How do I daemonize an arbitrary script in unix?

I'd like a daemonizer that can turn an arbitrary, generic script or command into a daemon.

There are two common cases I'd like to deal with:

1. I have a script that should run forever. If it ever dies (or on reboot), restart it. Don't let there ever be two copies running at once (detect if a copy is already running and don't launch it in that case).

2. I have a simple script or command line command that I'd like to keep executing repeatedly forever (with a short pause between runs). Again, don't allow two copies of the script to ever be running at once.

Of course it's trivial to write a "while(true)" loop around the script in case 2 and then apply a solution for case 1, but a more general solution will just solve case 2 directly since that applies to the script in case 1 as well (you may just want a shorter or no pause if the script is not intended to ever die (of course if the script really does never die then the pause doesn't actually matter)).

Note that the solution should not involve, say, adding file-locking code or PID recording to the existing scripts.

More specifically, I'd like a program "daemonize" that I can run like

% daemonize myscript arg1 arg2

or, for example,

% daemonize 'echo `date` >> /tmp/times.txt'

which would keep a growing list of dates appended to times.txt. (Note that if the argument(s) to daemonize is a script that runs forever as in case 1 above, then daemonize will still do the right thing, restarting it when necessary.) I could then put a command like above in my .login and/or cron it hourly or minutely (depending on how worried I was about it dying unexpectedly).

NB: The daemonize script will need to remember the command string it is daemonizing so that if the same command string is daemonized again it does not launch a second copy.

Also, the solution should ideally work on both OS X and linux but solutions for one or the other are welcome.

EDIT: It's fine if you have to invoke it with sudo daemonize myscript myargs.

(If I'm thinking of this all wrong or there are quick-and-dirty partial solutions, I'd love to hear that too.)

PS: In case it's useful, here's a similar question specific to python.

And this answer to a similar question has what appears to be a useful idiom for a quick-and-dirty demonizing of an arbitrary script:

Docker command can't connect to docker daemon

I want to make a move to docker so I've just started to mess around with it. I've installed docker on a virtualbox ubuntu 15.10 installation and as suggested here I then tried running a basic nginx docker image:

$ docker run --name mynginx1 -P -d nginx
Cannot connect to the Docker daemon. Is the docker daemon running on this host?

So I checked out whether docker was running:

$ sudo service docker status
● docker.service - Docker Application Container Engine
   Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
   Active: active (running) since vr 2015-11-06 08:41:48 CET; 15min ago
     Docs: https://docs.docker.com
 Main PID: 7542 (docker)
   CGroup: /system.slice/docker.service
           └─7542 /usr/bin/docker daemon -H fd://

nov 06 08:41:47 kramer65-VirtualBox systemd[1]: Starting Docker Application Container Engine...
nov 06 08:41:47 kramer65-VirtualBox docker[7542]: time="2015-11-06T08:41:47.900410966+01:00" level=info msg="API ...ock"
nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time="2015-11-06T08:41:48.033514149+01:00" level=info msg="Fire...lse"
nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time="2015-11-06T08:41:48.141594321+01:00" level=info msg="Defa...ess"
nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time="2015-11-06T08:41:48.416294436+01:00" level=warning msg="Y...it."
nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time="2015-11-06T08:41:48.565507576+01:00" level=info msg="Load...rt."
nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time="2015-11-06T08:41:48.567907022+01:00" level=info msg="Load...ne."
nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time="2015-11-06T08:41:48.567945214+01:00" level=info msg="Daem...ion"
nov 06 08:41:48 kramer65-VirtualBox docker[7542]: time="2015-11-06T08:41:48.567969891+01:00" level=info msg="Dock....9.0
nov 06 08:41:48 kramer65-VirtualBox systemd[1]: Started Docker Application Container Engine.
Hint: Some lines were ellipsized, use -l to show in full.

This suggests that the docker daemon is actually already running, but to be sure I just started the docker daemon manually:

$ sudo docker daemon
INFO[0000] API listen on /var/run/docker.sock           
INFO[0000] [graphdriver] using prior storage driver "aufs" 
INFO[0000] Firewalld running: false                     
INFO[0000] Default bridge (docker0) is assigned with an IP address XXX.XX.X.X/XX. Daemon option --bip can be used to set a preferred IP address 
WARN[0000] Your kernel does not support swap memory limit. 
INFO[0000] Loading containers: start.                   

INFO[0000] Loading containers: done.                    
INFO[0000] Daemon has completed initialization          
INFO[0000] Docker daemon                                 commit=76d6bc9 execdriver=native-0.2 graphdriver=aufs version=1.9.0

I then tried running the image again, but with the same result:

$ docker run --name mynginx1 -P -d nginx
Cannot connect to the Docker daemon. Is the docker daemon running on this host?

I tried sudo'ing the command, but to no avail. Does anybody know what I'm doing wrong here? All tips are welcome!

What is the minUptime

I am using forever with my project. What do these options do:

• minUptime
• spinSleepTime

I didn't understand from GitHub page.

Getting pids from ps -ef |grep keyword

I want to use ps -ef | grep "keyword" to determine the pid of a daemon process (there is a unique string in output of ps -ef in it).

I can kill the process with pkill keyword is there any command that returns the pid instead of killing it? (pidof or pgrep doesnt work)

What is the de facto library for creating Python Daemons

I am attempting to use the python-daemon library which seemed to me to be the safest way to create a Daemon without forgetting anything. The documentation is quite poor, being just PEP 3143.

On the other hand, I have found a lot of links to Sander Marechal's A simple unix/linux daemon in Python. This looks to be a nicer solution or though I have not yet attempted to use it.

Edit: I have used Sander Marechal's solution and it seems to work nicely.

So what is the de facto way in the Python community to create a Daemon, is it one of these libraries, or simply doing it all yourself (forking twice etc.)?

Also, you would think that any library with a PEP would be a far better choice since it is closer to a comprehensive way of creating a Daemon (or at least a more standard way) than any other solution. So what is the deal with this python-daemon package, would it ever be included in the standard library?

Is it possible to set up MongoDB in a shared hosting environment? [closed]

I'm using GoDaddy and would like to use MongoDB for a pet project. I'm not sure it is possible though, since it has to be running the daemon, but, it doesn't hurt to ask, is there a way?

EDIT: They've closed the question, but if anybody stumbles upon this post with the same question:

While you cannot set up MongoDB in a traditional share environment, thanks to the magic of the Cloud you can now find Free Mongo Hosting in places like:

https://mongolab.com/welcome/

https://www.mongohq.com/home

https://manage.windowsazure.com (via mongolab)