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The vast majority of custom metrics will be part of custom compiled devices. As an example, let’s assume you’re a device author and your device sends messages to a web service. You’d like to track the duration of the web service call, the upload volume (bytes uploaded) and rate (bytes per second) as well as the same metrics on the download side. You also want to track the message size sent to the service.
For tracking operation duration, you will need a histogram. You will also need a histogram to track the message size, transfer rate, and total transfer volume (one histogram for upload, and one for download).
Connexion’s BaseDevice class, from which all custom devices derive, contains scaffolding for declaring metrics. There are three methods exposed for creating metrics: GetOrCreateCounter, GetOrCreateGauge, and GetOrCreateHistogram. The MetricsProvider is also exposed should you need more advanced functionality.
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Connexion’s metrics implementation is closely related to the prometheus-net library. Many of our conventions and signatures mimic those of this library. |
Your metrics should be created in the InitializeMetrics() override. By using this method, your metrics will automatically be updated as users enable and disable metrics via the UI. Let’s look at an example device class:
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public class MetricSample : BaseDevice<MetricSampleConfiguration>
{
private IHistogram m_SendDurationHistogram; // measure the time taken to send the payload
public override void Start()
{
// make sure you call InitializeMetrics
InitializeMetrics();
}
protected override void InitializeMetrics()
{
// construct your metrics here
m_SendDurationHistogram = GetOrCreateHistogram("MyDevice.send_duration_in_s", // name of your metric. See notes about X.y syntax
"The duration (in seconds) to send to the foo service", // description
new HistogramConfiguration // configuration
{
LabelNames = new[] { "Group", "Tab", "Channel", "ChannelKey" }, // associate this metric with the owner channel
Buckets = new double[] { 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10 } // buckets (in seconds)
}).WithLabels(MessageChannel.GroupName, MessageChannel.TabName, MessageChannel.ChannelName, MessageChannel.ChannelKeyString);
}
public override Task ProcessMessageAsync(IMessageContext context, CancellationToken cancellationToken)
{
// ...your code
using (m_SendDurationHistogram.NewTimer()) // the Histogram.NewTimer() method is used to measure the wrapped methods duration.
{
await SendToFooServiceAsync(...).ConfigureAwait(false);
}
// ... your code
}
} |