Statistic Collection

The stats hook collects statistics about nodes. Currently the following metrics are collected:

Identifier	Unit	Description
skipped	samples	Skipped samples and the distance between them
reordered	samples	Reordered samples and the distance between them
gap_sent	seconds	Inter-message timestamps (as sent by remote)
gap_received	seconds	Inter-message arrival time (as received by this instance)
owd	seconds	One-way-delay (OWD) of received messages

If the node to which this hook is attached an rtp node-type, the following additional statistics are collected from the RTP reception reports. The contains details about the quality of service as seen be the receiver.

Identifier	Unit	Description
rtp.loss_fraction	percent	Fraction lost since last RTP SR/RR.
rtp.pkts_lost	packets	Cumulative number of packets lost.
rtp.jitter	seconds?	Inter-arrival jitter

For each of the metrics the following moments / attributes are collected:

Moment	Type	Description
last	float	The last collected value.
highest	float	The highest/largest collected value.
lowest	float	The lowest/smallest collected value.
mean	float	The mean across all collected values.
var	float	The variance across all collected values.
stddev	float	The standard deviation across all collected values.
total	integer	The total number of collected values.

Implementation

The source code of the hook is available here: https://github.com/VILLASframework/node/blob/master/lib/hooks/stats.cpp

Configuration

	Format Object (object) or Format Name (string) (format_spec)
buckets	integer Default: 20 The number of buckets which should be used for the underlying histograms.
warmup	integer Default: 500 Use the first warmup samples to estimate the bucket range of the underlying histograms.
verbose	boolean Default: false Include full dumps of the histogram buckets into the output.
output	string Default: "/dev/stdout" The file where you want to write the report to. If omitted, stdout (the terminal) will be used.
enabled	boolean Default: true An optional field which can be used to disable a hook.
priority	integer Default: 99 The priority of this hook which determines the order in which hooks are executed. Hooks with a lwoer priority are executed before ones with a higher priority. If no priority is configured, hooks are executed in the order they are configured in the configuration file.

{

• "format": "villas.human",
• "buckets": 20,
• "warmup": 500,
• "verbose": false,
• "output": "/dev/stdout",
• "enabled": true,
• "priority": 99

}

Example

node/etc/examples/hooks/stats.conf

stats = 1

nodes = {
    signal_node = {
        type = "signal"
        signal = "mixed"
        values = 5
        rate = 50

        in = {
            hooks = (
                {
                    type = "stats"

                    verbose = true
                    warmup = 10
                    buckets = 25
                }
            )
        }
    }
}

paths = (
    {
        in = "signal_node"
    }
)