Prometheus only scrapes one pod

Question

I'm using Prometheus to scrape metrics from my pods. The application I'm interested in is replicated a couple of times with one service providing access. Prometheus uses this service to scrape the metrics. In my app the metrics are setup as follows:

import * as Prometheus from 'prom-client';

const httpRequestDurationMicroseconds = new Prometheus.Histogram({
    name: 'transaction_amounts',
    help: 'Amount',
    labelNames: ['amount'],
    buckets: [0, 5, 15, 50, 100, 200, 300, 400, 500, 10000],
});

const totalPayments = new Prometheus.Counter('transaction_totals', 'Total payments');

I'm using helm to install Prometheus and the scrape config looks like this:

prometheus.yml:
  rule_files:
    - /etc/config/rules
    - /etc/config/alerts

  scrape_configs:
    - job_name: prometheus
      static_configs:
        - targets:
          - localhost:9090
    - job_name: transactions
      scrape_interval: 1s
      static_configs:
        - targets:
          - transaction-metrics-service:3001

I can see the metrics inside prometheus, but it seems to be from just one pod. For example, in Prometheus, when I query for transaction_totals it gives:

I don't think that the instance label can uniquely identify my pods. What should I do to be able to query all pods?

Answer 1

Instead of using a static_config that scrapes just one host, try using kubernetes_sd_configs Kubernetes Service Discovery as provided by Prometheus. Your config file would look something like this:

- job_name: 'kubernetes-pods'

  kubernetes_sd_configs:
  - role: pod

  relabel_configs:
  # only scrape when annotation prometheus.io/scrape: 'true' is set
  - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_scrape]
    action: keep
    regex: true
  - source_labels: [__meta_kubernetes_pod_annotation_prometheus_io_path]
    action: replace
    target_label: __metrics_path__
    regex: (.+)
  - source_labels: [__address__, __meta_kubernetes_pod_annotation_prometheus_io_port]
    action: replace
    regex: (.+):(?:\d+);(\d+)
    replacement: ${1}:${2}
    target_label: __address__
  - action: labelmap
    regex: __meta_kubernetes_pod_label_(.+)
  - source_labels: [__meta_kubernetes_namespace]
    action: replace
    target_label: kubernetes_namespace
  - source_labels: [__meta_kubernetes_pod_name]
    action: replace
    target_label: kubernetes_pod_name

and then add the annotation to your Kubernetes Deployment yaml config like this:

kind: Deployment

...

spec:
  template:
    metadata:
      annotations:
        prometheus.io/scrape: "true"
        prometheus.io/port: "<< PORT OF YOUR CONTAINER >>"

You can see a full working example here.