kubernetes-training

Prometheus server

1. Retrivial :pull service data
2. Storage : stores metric data
3. HTTP server: accepts queries

   Target and Metrics

• Servers
• application
• database

What units are monitored of those targets?

• CPU status
• Memory disk
• Requests

Metrics

• Metrics entries: TYPE and HELP attributes
• HELP: description of what the metric is
• TYPE: 3 types
  1. Counter type: how many times X happend?
  2. Gauge: what is the current value of X now?
  3. Histogram: how big of a request incoming?

How prometheus pull metrics data from target?

• Data is pulled from the HTTP endpoints, must be in the format the prometheus understands
• For some endpoints, metrics are available by default
• For some others: the exporter (e.g: Elastic search) fetches the metric from the target, convert the metric to the correct format, then expose the metric so that prometheus can scrape them. We then will have to configure prometheus to scrape those endpoints.

  Metrics

Gauges

• Metrics that can go up or down: current measurement
• Set(), Inc(), Dec()

  Counter

• Cumulative counts overtime
• Counter only go up, unless crash
• Inc(), Add()
• PromQL: rate(), irate(), increase()

  Summaries

• Distribution of request latency or set of numeric values

Prometheus operator

1. Custom resources:
   • Alert Manager
   • Prometheus rule
   • Alertmanger config
   • service monitor
   • pod monitor

Exporter

3 components:

• Exporter application (mongodb image instance in a pod)
• Service
• ServiceMonitor : P must know about the endpoint ready to be scraped

helm show values prometheus-community/prometheus-mongodb-exporter > values.yaml

-> command to make edit to the exporter

after making edit, run

helm install mongodb-exporter prometheus-community/prometheus-mongodb-exporter -f values.yaml