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 is of type Real-Time Protocol (RTP & RTCP), the following additional statistics are collected from the RTP receiption 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 packtes lost.
rtp.jitter	seconds?	Interarrival jitter

For each of the metrics the following moments / attrbributes 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://git.rwth-aachen.de/acs/public/villas/node/blob/master/lib/hooks/stats.cpp

Configuration

format (string: "json" | "matlab" | "human") = "human"

The output format used to print the statistics at shutdown.

buckets (integer) = 20

The number of buckets which should be used for the underlying histograms.

warmup (integer) = 500

Use the first warmup samples to estimate the bucket range of the underlying histograms.

verbose (boolean) = false

Include full dumps of the histogram buckets into the output.

output (string: uri)

The file where you want to write the report to. If omitted, stdout (the terminal) will be used.

Example

nodes = {
        udp_node = {
                type = "socket"

                in = {
                        address = "*:12000"

                        hooks = (
                                {
                                        type = "stats"

                                        verbose = true
                                        warmup = 100
                                        buckets = 25

                                        output = "stats.log"
                                        format = "json"
                                }
                        )
                }
                out = {
                        address = "127.0.0.1:12000"
                }
        }
}