Monitoring and Metrics

An updated demo can be found in the james-world/monitoring-demo repo - leaving this here to preserve context from recorded demos, but the new repo uses docker-compose and is much easier to run up.

Demos accompanying the brown bag talk of the same name.

Demo1 - Installing and Running Prometheus

The easiest way to get Prometheus up and running is with it's maintained docker image prom/prometheus. The image looks for a YAML configuration file at /etc/prometheus.yml and stores it's time series database (tsdb) at /prometheus.

This first demo runs up a docker container with local bind mounts to map a simple configuration file and folder for the database.

The minimal configuration sets a global time interval for scraping jobs, and a single job to scrape prometheus itself.

Execute .\run_demo.ps1 from a powershell console to fire up a prometheus container and open a browser an the prometheus UI.

Demo2 - Installing and Running Prometheus in Kubernetes

Here we use a pod spec that uses an emptyDir volume mount for the tsdb. The emptyDir volume type is a folder provisioned in local node storage which is deleted when the pod is destoyed. The configuration is passed via a config map.

Prerequisits: kubectl is installed and pointing to a valid cluster (minikube/docker desktop is fine)

To configure this from the Demo2 folder run:

kubectl create configmap prometheus-config --from-file=prometheus.yml

Then create the pod with:

k apply -f prometheus_pod.yaml

In order to test everything is working, port forward using

kubectl port-forward prometheus 9123:9090

and open http://localhost:9123.

Updating the config map

Use this trick to update a configmap created from a file:

kubectl create configmap prometheus-config --from-file=prometheus.yml --dry-run -o yaml | kubectl apply -f -

Then connect to the prometheus server and send a SIGHUP to the prometheus process to get it to pick up the new config - wait for a minute, because it takes a while for the configmap change to be reflected in the pod (this is a kubernetes limitation).

kubectl exec -it prometheus sh
kill -1 1
exit

Demo3 - Adding a Pod that publishes metrics

Prerequisits: kubectl is installed and pointing to a valid cluster (minikube/docker desktop is fine)

The Demo3 folder contains a simple DotNet web api project - it's the standard starter template created with dotnet new webapi.

To this project the following additions have been made:

• The prometheus client has been added with dotnet add package prometheus-net.AspNetCore.
• A standard asp dotnet core multistage Dockerfile has been created, and an environment variable ENV ASPNETCORE_URLS http://*:80 added publish on the public networks (instead of just localhost)
• A kube pod spec has been added (this has an annotation we'll come back to later)

The startup has been modified as the comments below indicate:

public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    app.UseHttpsRedirection();

    app.UseRouting();
    // capture http metrics
    app.UseHttpMetrics();

    app.UseAuthorization();

    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
        // expose /metrics endpoint
        endpoints.MapMetrics();
    });
}

The WeatherForecastController.cs has been altered to capture a Counter metric.

Build the docker container:

• docker build -t jamesworld\monitoring-dotnetsample:1.0 .\Demo3\src\DotNetSample\.

Demo 4 - A slightly more serious Kuberbetes deployment

Using a monitoring namespace, cluster role and scrape configs.

• prometheus_namespace.yaml defines a monitoring namespace and cluster role and cluster role binding for the prometheus service. Deploy with kubectl apply -f prometheus_namespace.yaml.
• Updated configuration in prometheus.yml ensures only pods carrying the prometheus.io/scrape annotation are collected. Deploy this with kubectl crete configmap prometheus-config -n monitoring --from-file=prometheus.yml --dry-run -o yaml | kubectl apply -f -
• promethues_deployment.yaml is a deployment of the kube pod into the monitoring namespace. kubectl apply -f prometheus_deployment.yaml takes care of that.

Demo 5 - The Stock App, with Prometheus and Grafana

Includes:

• A simple ASP.NET Core 3.1 app that makes use of the prometheus-net.AspNetCore library to expose a metrics endpoint and a custom product_stock_levels Prometheus Gauge
• A grafana instance with pre-configured dashboards drawing from a prometheus instance.
• A jmeter load test to exercise the app.

Prerequists:

• To run the load tests, jmeter should be installed
• To use the SampleApiCalls.rest to send manual requests, include the Visual Studio Code REST Client plugin.
• Docker is installed
• Create a local named docker network with docker network create demo

Build the docker containers:

• docker build -t jamesworld\acme:1.0 .\Demo5\src\Acme\.
• docker build -t jamesworld\acme:1.0 .\Demo5\src\Grafana\.

Run .\Demo5\run_demo.ps1 from a powershell prompt to start the docker containers