What Is The Job Label In Prometheus?

The job label in Prometheus organizes monitored instances or endpoints into logical groups. It is automatically added to metrics scraped from targets defined in the same scrape configuration block in prometheus.yml.

Overview

The job label groups instances (e.g., servers, containers) with similar functionality. Each target in a job is uniquely identified by its instance label (host and port). Defined using the job_name field in prometheus.yml, this label is frequently used in PromQL queries to filter or group metrics.

Example

In the following scrape configuration:

scrape_configs:
  - job_name: 'api-servers'
    static_configs:
      - targets: ['192.168.1.101:8080', '192.168.1.102:8080']
  - job_name: 'db-servers'
    static_configs:
      - targets: ['192.168.1.201:5432', '192.168.1.202:5432']

Metrics scraped from these targets include:

• API Servers:
  http_requests_total{job="api-servers", instance="192.168.1.101:8080"} 42 http_requests_total{job="api-servers", instance="192.168.1.102:8080"} 56

• Database Servers:
  db_queries_total{job="db-servers", instance="192.168.1.201:5432"} 120
db_queries_total{job="db-servers", instance="192.168.1.202:5432"} 98

Common Uses

The job label is integral for filtering and aggregating metrics in PromQL. For example, to fetch metrics from all API servers:

http_requests_total{job="api-servers"}

To sum requests across all API server instances:

sum(http_requests_total{job="api-servers"})

It also helps in alerting configurations. For instance, you can alert when no API server targets are available:

alert: NoTargetsAvailable
expr: up{job="api-servers"} == 0
for: 5m
labels:
  severity: critical
annotations:
  summary: "No targets available for API servers"

In tools like Grafana, the job label can group or filter metrics for dashboards.

Best Practices

Choose clear, descriptive names for job_name (e.g., api-servers or db-cluster). Group targets logically—avoid mixing unrelated instances. Use the instance label alongside job for precise monitoring.

The job label simplifies metric organization, queries, and alerting, making it a cornerstone of effective monitoring in Prometheus.

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