d. Prometheus

Prometheus works by pulling (scraping) metrics from each service endpoint at a configured interval and storing the time-series data locally.

Create the file setup/prometheus/prometheus.yml:

prometheus.yml
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scrape_configs:

  - job_name: 'GatewayMetrics'
    metrics_path: '/gateway/actuator/prometheus'
    scrape_interval: 1s
    static_configs:
      - targets:
        - gateway:8080
        labels:
          application: 'Gateway Application'

  - job_name: 'AuthMetrics'
    metrics_path: '/auth/actuator/prometheus'
    scrape_interval: 1s
    static_configs:
      - targets:
        - auth:8080
        labels:
          application: 'Auth Application'

  - job_name: 'AccountMetrics'
    metrics_path: '/accounts/actuator/prometheus'
    scrape_interval: 1s
    static_configs:
      - targets:
        - account:8080
        labels:
          application: 'Account Application'

Key points:

Field Description
job_name Logical name for the scrape job; appears as a label in all collected metrics.
metrics_path Must match the base-path defined in each service's application.yaml.
targets Uses Docker service hostnames (gateway, auth, account) and the internal port 8080.
scrape_interval How often Prometheus pulls fresh metrics from each target.

Once the stack is running, access the Prometheus UI to query metrics directly:

http://localhost:9090/