It can happen that pcp-htop is presented multiple definitions
of the same dynamic meter, e.g. if /etc/pcp/htop/meters has a
definition matching one in ~/.config/htop/meters - instead of
exiting with a duplicate metric error provide more meaningful
diagnostics (on close) and also just skip over such entries.
System files override home directories which overrides those
found below the current working directory.
Also fix the derived metric error diagnostic; because this is
using CRT_fatalError, which is like perror(3), we must give a
meaningful prefix (like program name) at the string end.
Several improvements to the way values are displayed in the
PCP platform DynamicMeter implementation:
- handle the initial 'caption' setting as with regular meters,
this required a new meter callback because we no longer have
just a single meter caption for the DynamicMeter case
- if no label is provided for a metric in a configuration file
use the short form metric name as a fallback
- honour the suffix setting in the configuration file
- convert metric values to the canonical units for htop (kbyte
and seconds), and use Meter_humanUnit when it makes sense to
do so.
Also improves the handling of fatal string error messages in a
couple of places, thanks to BenBE for the review feedback.
This commit is based on exploratory work by Sohaib Mohamed.
The end goal is two-fold - to support addition of Meters we
build via configuration files for both the PCP platform and
for scripts ( https://github.com/htop-dev/htop/issues/526 )
Here, we focus on generic code and the PCP support. A new
class DynamicMeter is introduced - it uses the special case
'param' field handling that previously was used only by the
CPUMeter, such that every runtime-configured Meter is given
a unique identifier. Unlike with the CPUMeter this is used
internally only. When reading/writing to htoprc instead of
CPU(N) - where N is an integer param (CPU number) - we use
the string name for each meter. For example, if we have a
configuration for a DynamicMeter for some Redis metrics, we
might read and write "Dynamic(redis)". This identifier is
subsequently matched (back) up to the configuration file so
we're able to re-create arbitrary user configurations.
The PCP platform configuration file format is fairly simple.
We expand configs from several directories, including the
users homedir alongside htoprc (below htop/meters/) and also
/etc/pcp/htop/meters. The format will be described via a
new pcp-htop(5) man page, but its basically ini-style and
each Meter has one or more metric expressions associated, as
well as specifications for labels, color and so on via a dot
separated notation for individual metrics within the Meter.
A few initial sample configuration files are provided below
./pcp/meters that give the general idea. The PCP "derived"
metric specification - see pmRegisterDerived(3) - is used
as the syntax for specifying metrics in PCP DynamicMeters.
