Re: Problems with GNU Parallel and ulimit

[ericbavier@openmailbox.org]

> On 08/15/2017 at 00:14 Arun Isaac writes:
> 
>> Leo Famulari writes:
>>
>>> On Mon, Aug 14, 2017 at 12:46:25PM +1000, Ben Woodcroft wrote:
>>>> On 14/08/17 12:31, Arun Isaac wrote:
>>>> > Does `parallel' work for anybody? When I run
>>>> > 
>>>> > $ ls | parallel echo
>>>> > 
>>>> > I get the following error message, and nothing happens.
>>>> It works fine for me using Guix on a foreign OS, and has since I can
>>>> remember.
>>>> ben
>>>
>>> Same here. Arun, can you give some more details about your system?
>>
>> This is probably a problem only on GuixSD systems. Could you try on
>> GuixSD instead of using Guix on a foreign distro?
> 
> I think you are correct. I run GuixSD and, after installing parallel I
> get ...
> 
> ***
> g1@g1 ~$ ls | parallel echo
> ...
> parallel: Warning: No more processes: Decreasing number of running jobs to 7.
> parallel: Warning: Raising ulimit -u or /etc/security/limits.conf may help.

The problem appears if you do not have 'perl' available in $PATH.  GNU parallel calls it recursively for a few tasks:

$ guix package -I | grep "perl"
$ echo $?
1
$ parallel echo ::: 1 2 3
...
parallel: Warning: Raising ulimit -u or /etc/security/limits.conf may help.
parallel: Error: No more processes: cannot run a single job. Something is wrong at 1.
$ guix environment --ad-hoc perl
[dev]$ parallel echo ::: 1 2 3
1
2
3

There is some path patching that goes on in the package recipe, but it must have gone out of sync in latest versions.  The 'post-install-test' phase wouldn't catch this particular error without '(setenv "PATH" "")'.

I wouldn't feel quite comfortable doing a "blind" update of the regex, since some mentions of "perl" I think are meant to be executed by remote hosts and so shouldn't be patched to absolute store references.

It might be useful to get Ole's opinion on this.

`~Eric

> I am not a parallel user so I can't comment further.
> 
> HTH - George