Re: Cron tasks?

Hello David.

I've got cron to work as expected by doing this:

1 - Create an "extra" image and add the necessary packages (cronie crontabs nss_wrapper uid_wrapper):

https://github.com/getupcloud/sti-ruby-extra/blob/1dfed4ca7ca153e261c880f0b036129c5d9011ca/1.9/Dockerfile#L18

We need to relax security here, otherwise neither crond nor crontab will work, since both are run as regular users:

https://github.com/getupcloud/sti-ruby-extra/blob/1dfed4ca7ca153e261c880f0b036129c5d9011ca/1.9/Dockerfile#L24-L26

2 - Create an script to activate nss_wrapper and (optionally) uid_wrapper:

https://github.com/getupcloud/sti-ruby-extra/blob/master/1.9/nss-wrapper-setup

libuid_wrapper is required by /usr/bin/crontab so it believes to be running as root.

In order to crond start it needs to have the current user in your passwd. You can achieve this by using nss_wrapper with a "fake" passwd file [1] and instruct everyone to use it [2]

3 - From your repo's (.sti|.s2i)/bin/run, "source" the wrapper and start crond.

if [ -x ${STI_SCRIPTS_PATH}/nss-wrapper-setup ]; then
source ${STI_SCRIPTS_PATH}/nss-wrapper-setup -u
crond-start
fi

I choose to run it from the same code container so it can reach the code itself.

Please, feedback is very appreciated.

Best Regards.

[1] https://github.com/getupcloud/sti-ruby-extra/blob/1dfed4ca7ca153e261c880f0b036129c5d9011ca/1.9/nss-wrapper-setup#L22-L27

[2] https://github.com/getupcloud/sti-ruby-extra/blob/1dfed4ca7ca153e261c880f0b036129c5d9011ca/1.9/nss-wrapper-setup#L29-L31

Mateus Caruccio

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On Tue, Feb 23, 2016 at 7:03 AM, Maciej Szulik <maszulik redhat com> wrote:

On 02/23/2016 10:41 AM, David Strejc wrote:

Does anyone have any experience with cron tasks as they were in OS v2?

v3 does not have cron support yet, there was a proposal already accepted
in k8s. In the following weeks/months I'll be working on implementing
such functionality.

I would like to let our developers maintain cron tasks through git .s2i
folder as it was in v2.
Is it good idea to build cron into docker image and link crontab to file
inside .s2i?

I'm not sure this will work as you expect. You'd still need a separate
mechanism that will actually trigger build, or other action when the
right time comes.

What I can suggest as a temporary solution is writing/deploying some
kind of cron scheduler inside of OpenShift.

Maciej

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