The problem to solve
A common way to start up services
Either you are using macOs, FreeBSD, or any Linux variant the idea is to simplify how process/services are keep up and running, without need to worry about special environments or paths.
A single run.yml file should be enough for start and supervise
the services, or used as a template within automation tools like
Saltstack, Ansible, etc.
Follow PID
In some cases it is required to supervise applications that daemonize by default. Normally this kind of applications create a pidfile every time they fork, the one can be used to follow subsequent forks and avoid creating a race condition between the supervisor trying to start again the process and the forks created by the application.
Example of a race condition while trying to supervise unicorn with runit:
In the example given below, after forking (kill -USR2 $PID), The supervisor in use
runit in this case, tries to start up again the application, since the
process that was supervising died, but instead enters into loop
because the application still up and running using the same port.
logging
When working in distributed “cloud” environments, centralized logging becomes a requirement, therefore it is desired to have availability to chose how and where to log, either to a local file, to a local file and to a remote server or only remotely either TCP or UDP.
To achive this, immortal is not only capable to write logs to a defined
file, but is also allows to specify an external logger, by specifying the -l
and -logger options example:
$ immortal -l /tmp/test.log -logger "logger -t test" my-app
In this case -loger is going to pass the Stander output/error to the
logger
Example logging to a file and to the system syslog using logger:
Service dependencies
By defining a require option the service will only start if all the services defined are running.
/usr/local/etc/immortal
|--foo.yml
|--bar.yml
`--www.yml
if www.yml contains:
require:
- foo
- bar
If service foo and bar are not running, the service will not start.