polo -- Prevents a program from running more than one copy at a time
The basic ideas come from the original Perl application solo
polo prevents a program from running more than one copy at a time; it is useful with cron to make sure that a job doesn't run before a previous one has finished.
usage: polo.py [-h] [--address ADDRESS] [--dir DIR] [--port PORT] [--timeout TIMEOUT] [--no-bind] --
command [command ...]
A Python version of solo
positional arguments:
command The command to execute
options:
-h, --help show this help message and exit
--address ADDRESS Address to listen on or to check
--dir DIR Working directory
--port PORT Port to listen on or to check
--timeout TIMEOUT Timeout when checking. Default: 1 second.
--no-bind Do not bind on address:port specified
Below the crontab settings to create some ssh tunnels. If any tunnel is broken due to network issue, cron will try to restart them in within 1 minute. If the tunnel is still work, cron will simply exit.
$ crontab -l
*/1 * * * * python solo.py --port 6432 --address 127.0.0.1 --no-bind -- /usr/bin/ssh zproxydev -fN
*/1 * * * * python solo.py --port 6442 --address 127.0.0.1 --no-bind -- /usr/bin/ssh zproxystaging -fN
*/1 * * * * python solo.py --port 6452 --address 127.0.0.1 --no-bind -- /usr/bin/ssh zproxyproduction -fN