Overview
This is an Erlang application which allows metrics to be sent to Mondemand.
Configuration
Mondemand requires the setting of one or more LWES channels to send stats and other events to. This is configured as an application variable. Either directly as
{ lwes_channel, {1, [ {"127.0.0.1", 20602} ] } }
or via a config located on the system somewhere
{ config_file, "/etc/mondemand/mondemand.conf" }
In addition if you want to collect stats from the erlang VM itself you can enable this with
{ vmstats, [ { program_id, erlang_vm } ] }
By default the vmstats will include scheduler utilization which can cause some increased CPU utilization under light loads, so if you wish to disable that you can as
{ vmstats, [ { program_id, erlang_vm }, {disable_scheduler_wall_time, true } ] }
Usage
Mondemand has the concept of two types of metrics
- Counters - values which typically increase until rolling back to 0
- Gauges - instantaneous values such as temperature (or more regularly a reseting counter or non-mondemand held counter).
Clients will typically add calls like
mondemand:increment (ProgramName, CounterName, AmountToIncrementBy).
for manipulating counters, and
mondemand:set (ProgramName, GaugeName, AmountToSetGaugeTo).
for setting gauges.
In addition both calls above accept an optional 4th parameter of a list of Key/Value pairs representing the context of the call.
Mondemand will add the hostname to all metrics sent to the central mondemand-server.