Forum: CFEngine Help
Subject: Re: renicing a process
Author: sauer
Link to topic: https://cfengine.com/forum/read.php?3,25092,25237#msg-25237
So, apparently this is a tad difficult, as "nice" and "priority" are not the
same thing. Further complicating things, AIX and HP-UX have completely
differnet values for the priority field than Linux (and each other), and RHEL5
has dynamic reprioritization enabled out of the box - so there is a range of
possible priorities for a given nice value.
So, I ended up with this process selection bundle:
body process_select nice_exact(p){
priority => irange("$(g.nice_to_priority[$(p)])",
"$(g.nice_to_priority[$(p)])");
process_result => "priority";
}
And the "g.nice_to_priority" is an array defined per-OS which maps the desired
nice value to a priority value. It doesn't work with the RHEL5 dynamic
prioritization, of course, but I figure that the cost of just running renice
periodically is lower than the cost of re-parsing "ps -o nice" myself. :)
For the record, the rest of the code looks essentially like this:
vars:
"nice" int => "5";
"pidfile" string => "/var/run/randomproc.pid";
"niceprocs" slist => getindices( "nice" );
"can_proc[$(niceprocs)]"
string => canonify( "$(niceprocs)" );
"pid[$(niceprocs)]"
string => readfile( "$(pidfile[$(niceprocs)])", "15");
classes:
"have_pid_$(can_proc[$(niceprocs)])"
expression => fileexists("$(pidfile[$(niceprocs)])");
processes:
"$(niceprocs)"
process_select => nice_exact("$(nice[$(niceprocs)])"),
restart_class => "renice_$(can_proc[$(niceprocs)])",
ifvarclass => "have_pid_$(can_proc[$(niceprocs)])",
action => if_elapsed("$(delay)"),
comment => "Make sure $(niceprocs) has priority $(nice[$(niceprocs)])";
commands:
"$(renice) $(nice[$(niceprocs)]) -p $(pid[$(niceprocs)])"
ifvarclass =>
"have_pid_$(can_proc[$(niceprocs)])&renice_$(can_proc[$(niceprocs)])";
Before I open a feature request to add an additional "nice" process selection
capability (most ps implementations do have a separate "nice" column), am I the
only person who's ever wanted to make a promise as to the nice value of a
process?
PS: it'd be super convenient to have a $(match.pid) or some similar variable
which contains the pid of the process whose name matched in a processes promise
-- but again, I'm hesitant to open the feature request if I'm the only one who
could use this. That's what the have_pid_x class is above; I check to see if
there's a pid file for the process, and that's good enough to tell if it's
running or not (in this situation).
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