Way to do ":background" without background?

[Carlos Peñas]

Hi I needed to fire a long running and unrelated to deploy task on each deploy (and on demand) And I noticed a :background" method but it says it is deprecated, so it whouldn't work in a future version of SSHKit. 

Is there an alternative to launch a task on background without stop capistrano's processing?

I tried to launch with & but obviously, while there's a  job in the session capistrano won't continue.

[Lee Hambley]

First of all, well read - the `:background => true` is deprecated, because backgrounding things is hard, and unreliable, basically as you might have seen all it does it `nohup` and `&` if memory serves.

So there's two things you can do, the one - as you alluded to is `&` on the end of the line. The other would be `nohup` yourself, it'd be interesting to know *what* you are trying to background, as weird processes refuse to play well in the background in different ways.

Let's see if we can solve this for you :)

[Carlos Peñas]

On Friday, 18 December 2015 17:03:17 UTC+1, Lee Hambley wrote:

First of all, well read - the `:background => true` is deprecated, because backgrounding things is hard, and unreliable, basically as you might have seen all it does it `nohup` and `&` if memory serves.

Yes I noticed :) I Like to be informed before ask 

 

So there's two things you can do, the one - as you alluded to is `&` on the end of the line. The other would be `nohup` yourself, it'd be interesting to know *what* you are trying to background, as weird processes refuse to play well in the background in different ways.

The whole thing is to put "on background" a three line bash script that makes a "aws ec2 wait snapshot-completed" (no loops, no forks, no services, straight and simple thing that can work or not, but doesn't affect the deploy) and inform of the result by slack, for a snapshot that I asked to create in the previous commands of the capistrano task. The task just creates an snapshot of the deployed app EBS, but these snapshots sometimes take a bit to complete, that's why I want to "fire and forget" that script (it gives independent feedback, also)

 

Let's see if we can solve this for you :)

Well I'm very aware of the imitations of nohups, job control and the like, perhaps I can mimic the :background to get my own "non-deprecated" background and do my own tests. I know that fork processes over ssh conections can work for certain use cases, but cannot be guaranteed for all the use cases ;)

Thanks!

[Lee Hambley]

Alright, so sounds good :) At least if you know the risks, you can easily replicate "background => true" functionality yourself, and provided you know what's involved, the reasons we're deprecating it need not apply to you. As well you seem to know, nohup and & together are important, and so can be redirecting stdout/err to a file that isn't bound to the SSH TTY that Capistrano creates.

Lee Hambley

http://lee.hambley.name/

+49 (0) 170 298 5667

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