matoski.com

Last time in were exposing some metrics for a golang application, but exposing the data is useless without having a way to visualise it or even store it somewhere in a location so we can analyze it when needed.

Some of the tools that we can use to do this are

• Prometheus
• cAdvisor
• Grafana

At this point, I will assume have a docker swarm cluster available and ready to use.

Let’s create a stack file that will allow us to replicate this one on another swarm easily. All the required resources are on github.com/ilijamt/gomeetupamsnov2018

We need some prerequisites first

• Network for the monitoring applications
• Node metrics exporter/prometheus
• Prometheus
• Grafana
• cAdvisor
• Application that will expose metrics

Let’s create a very simple application that will build a small service that will expose various metrics.

main.go

package main

import (
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"net/http"
)

func main() {
	prometheus.MustRegister(prometheus.NewGauge(prometheus.GaugeOpts{
		Name: "version",
		Help: "Version information about this service",
		ConstLabels: map[string]string{
			"version": "v1.1.51",
			"service": "demo",
		},
	}))

	http.Handle("/metrics", promhttp.Handler())
	if err := http.ListenAndServe(":2112", nil); err != nil {
		panic(err)
	}
}

We need to create 2 services off the code and build create the docker images, running these commands will build and tag the images

docker build demo-v1 -t gomeetup-demo-v1:latest
docker build demo-v2 -t gomeetup-demo-v2:latest

I think everyone should be able to understand the stack file bellow.

stack.yaml

version: "3"

networks:
  monitoring:
  api:

services:
  demo_service_v1:
    image: gomeetup-demo-v1:latest
    deploy:
      mode: replicated
      replicas: 6
    networks:
      - monitoring
      - api
  demo_service_v2:
    image: gomeetup-demo-v2:latest
    deploy:
      mode: replicated
      replicas: 4
    networks:
      - monitoring
      - api
  cadvisor:
    image: google/cadvisor:latest
    deploy:
      mode: global
    ports:
      - "8080:8080"
    volumes:
      - /var/lib/docker/:/var/lib/docker
      - /dev/disk/:/dev/disk
      - /sys:/sys
      - /var/run:/var/run
      - /:/rootfs
      - /dev/zfs:/dev/zfs
    networks:
      - monitoring
  grafana:
    image: grafana/grafana
    ports:
      - "3000:3000"
    volumes:
      - ./data/grafana:/var/lib/grafana:rw
    deploy:
      mode: replicated
      replicas: 1
    environment:
      - GF_SECURITY_ADMIN_PASSWORD=admin
      - GF_USERS_ALLOW_SIGN_UP=false
    networks:
      - monitoring
  prometheus:
    image: prom/prometheus:latest
    ports:
      - '9090:9090'
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml:ro
      - ./data/prometheus:/prometheus:rw
    deploy:
      mode: replicated
      replicas: 1
    networks:
      - monitoring

We also need to create the configuration for prometheus so we can get the data automatically off the services.

global:
  evaluation_interval: 15s
  scrape_interval: 15s

scrape_configs:
  - job_name: services
    metrics_path: "/metrics"
    scrape_interval: 10s
    dns_sd_configs:
      - names:
          - 'tasks.demo_service_v1'
          - 'tasks.demo_service_v2'
        type: 'A'
        port: 2112
  - job_name: cadvisor
    metrics_path: /metrics
    scrape_interval: 30s
    dns_sd_configs:
      - names:
          - "tasks.cadvisor"
        type: 'A'
        port: 8080

What this will do is create 2 jobs that will collect the metrics, at their specified periods, the tasks.is something you can use in docker swarm to get all the IP addresses associated with the service so the node exporter/prometheus can get all the data without us having to manually configure it.

Now to deploy this stack we can just issue the command bellow.

docker stack deploy gomeetupamsnov -c stack.yml

This will spin up all the necessary services required for this to work, after which we will be able to access.

• cAdvisor on port 8080
• Prometheus on port 9090
• Grafana on port 3000

Load up some dashboards, there are plenty available on grafana’s page.

And voila we have some dashboards with information relevant to us.

Golang process data regarding cAdvisor

Golang process data regarding the demo services

Docker data from cAdvisor

Next steps

• Automatic configuration of jobs, we can use consul for this, so anytime a new service is added we pick it up right away
• Adding node exporter instead of full prometheus inside the swarm (done for simplicity)
• Setting up alerting based on our parameters