collector

Overview ¶

Package collector is the core instrumentation package. Modifications shouldnt be needed. The purpose of LPM is to easily integrate a propagation measurement app with the prometheus project. Collector doesn't provide any measurment methods, but it provides an abstraction layer where adding own custom network metrics is easier than ever.

It provides a singleton instance of LPMInstance, which itself has the metric data taken from the measurements, the information of the neighbor nodes and the prometheus registry. Collector takes care of creating the necesary prometheus collectors, running the measurements in the specified intervals between the specified nodes and serving them over http in localhost:8090/metrics.

Using Collector ¶

Three main things should be implemented when using Collector. Here we provide an example of usage:

## Implementing measurement methods As Collector doesnt provide any measurement method, an implementation must be added for every metric that you want to take. The measurement methods should have the following syntax: 'func measureMetric(neighborIP string) float64' Where measureMetric is the unique name of the method you are implementing (for example measureRtt or measureJitter) As argument it should provide only one, as a string, that it should be used for specifying the ip we want to run the test against, as Collector will later call this method by using that field. The return should be a float64 always, which contains the result of the final test. Errors should be managed inside the method. If an error occur, an invalid value should be used. For example, if while measuring rtt you get an error, you may return a negative value so when the metric is logged, the value can be interpreted as such. Here a basic example of a measuring method:

------------------------------------------------------- func measureRtt(neighborIP string) float64 {

log.Infof("Measuring rtt")

out, err := exec.Command("ping", neighborIP, "-c", "10", "-q").Output()

if err != nil {
	log.Errorf("Could not measure Rtt. Ping responds: %v", err)
	return -1
}

// Regular expression pattern pattern := `rtt min/avg/max/mdev = [0-9.]+/([0-9.]+)/`

// Compile the regular expression re := regexp.MustCompile(pattern)

// Find the first match in the input string match := re.FindStringSubmatch(string(out[:]))

if len(match) < 2 {
	log.Errorf("Could not measure Rtt. Check the connection between the two nodes.")
	return -1
}

// Print the result log.Infof("Rtt between two links: %s", match[1])

rtt, _ := strconv.ParseFloat(match[1], 64) return rtt } ------------------------------------------------------------------

HTTP Exposition ¶

The Registry implements the Gatherer interface. The caller of the Gather method can then expose the gathered metrics in some way. Usually, the metrics are served via HTTP on the /metrics endpoint. That's happening in the example above. The tools to expose metrics via HTTP are in the promhttp sub-package.

Code structure: ¶

The main singleton can be found in the lpminstance.go file, along its initiation methods.

In collector.go the methods that run the instance are defined.

In collector.go you can find the implementation of the methods that define the prometheus collectors saved in the registry

All exported functions and methods are safe to be used concurrently unless specified otherwise.