[Hawkular-dev] About configuration

[Thomas Segismont]

Hi everyone,

Yesterday Lukas asked on IRC if there was a discussion about 
configuration. AFAIK, there wasn't, hence I'm sharing how we support 
configuration in metrics.

# Metrics REST server

The REST server runs on top of Wildfly.

Configuration is a set of key/value pairs (configuration properties) 
defined by the following sources, in order of precedence:

* system properties (-Dkey=value)
* external java.util.Properties file, which path is defined by the 
metrics.conf system property; by default, <user.home>/.metrics.conf is 
used (if it exists)
* internal java.util.Properties file (META-INF/metrics.conf)

The rationale behind is that the system should be able to:

1. start with reasonable defaults
2. switch to another configuration easily

# pTrans

pTrans is different because it's a standalone application, so it's much 
easier to follow the daemon configuration habits.

pTrans takes a path to a properties configuration file as a program 
argument. This argument is mandatory.

# Configuration file format.

metrics started with properties file and I think it's fine.

But if we feel the need for a more structured format, we should pick 
something which can be easily parsed by a variety of programming 
languages, especially languages widely used for administration (Python 
and Ruby).


Regards,
Thomas