Measure latency #

We’ll use the go-demo-5 application to measure latency, so our first step is to install it.

GD5_ADDR=go-demo-5.$LB_IP.nip.io

kubectl create namespace go-demo-5

helm install go-demo-5 \
    https://github.com/vfarcic/go-demo-5/releases/download/0.0.1/go-demo-5-0.0.1.tgz \
    --namespace go-demo-5 \
    --set ingress.host=$GD5_ADDR

We generated an address that we’ll use as an Ingress entry-point, and we deployed the application using Helm. Now we should wait until it rolls out.

kubectl -n go-demo-5 \
    rollout status \
    deployment go-demo-5

Before we proceed, we’ll check whether the application is indeed working correctly by sending an HTTP request.

curl "http://$GD5_ADDR/demo/hello"

The output should be the familiar hello, world! message.

Get the duration of requests entering the system #

Now, let’s see whether we can, for example, get the duration of requests entering the system through Ingress.

open "http://$PROM_ADDR/graph"

If you click on the - insert metrics at cursor - drop-down list, you’ll be able to browse through all the available metrics. The one we’re looking for is nginx_ingress_controller_request_duration_seconds_bucket. As its name implies, the metric comes from NGINX Ingress Controller, and provides request durations in seconds and grouped in buckets.

Please type the expression that follows and click the Execute button.

nginx_ingress_controller_request_duration_seconds_bucket

In this case, seeing the raw values might not be very useful, so please click the Graph tab.

You should see graphs, one for each Ingress. Each is increasing because the metric in question is a counter. Its value is growing with each request.

🔍 A Prometheus counter is a cumulative metric whose value can only increase, or be reset to zero on restart.

Calculate the rate of requests #

What we need is to ...