[rrd-users] Help in need when writing gangnlia python metrics modules

[Robinson Tiemuqinke]

Hi, all,

  I'm writing a ganglia python metrics module to monitor haproxy  software's performance. I'm following the steps at http://ganglia.wiki.sourceforge.net/ganglia_gmond_python_modules. the modules does send data back to gmetad but I still don't understand the following parameters for metrics' descriptors, could you or someone shed a light into this:

The following paragraph is excerpt from the html page:

-----------------------------------------------------------------
name: name of the metric 
call_back: function to call when collecting metric data 
time_max: maximum time in seconds between metric collection calls 
value_type: string | uint | float | double 
units: unit of your metric 
slope: zero | positive | negative | both 
format: format of your metric 
description: description of your metric (which is visible in web frontend if you hover over host metric graph) 
group: group of your metric (metrics in the web frontend hostview is grouped by this)
-----------------------------------------------------------------------

My questions are:

1, how can I specify RRD file's heartbeat rate here?

2, How can I specify a metric's type (COUNTER/GAUGE/DERIVE/etc)? And it value range (min--max)?

3, when the metric has a large int (between 2**32 and 2**64) value, which 'value_type' should I specify? Is the 'uint' -- probably means unsigned int -- good enough?

3.1, If I specify 'uint' for 'value_type', and the metrics has a negative value '-1' to specify the problematic situation where data is not retrievable, then what will happen? 

4, what do the 'slope' values mean? And how to specify it for a particular metric?

Thanks a lot!

--Robinson