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Version: 2.0.x


A MetricLabel metadata represents a key-value pair that allows analyzing metrics at an additional level of granularity. For example, if a metric tracks the response time of a service, labels could be used to create separate versions that track response times for different clients.

ZIO Metrics has a label based dimensional data model where we have a metric name and just a list of key-value pairs attached to that metric name. So labels are the first-class citizen in ZIO Metrics. In monitoring dashboards, we can find or filter metrics using these labels.

For example, we can append following labels (dimensions) to our metric aspects:

  • Endpoint (/api/users, /api/documents)
  • HTTP Method (POST, GET)
  • Deployment Environment (Staging, Production)
  • HTTP Response Code
  • Error code (404, 503)
  • Datacenter Zone (us-east, eu-west)
import zio._
import zio.metrics._

val counter = Metric.counter("http_requests")
MetricLabel("env", "production"),
MetricLabel("method", "GET"),
MetricLabel("endpoint", "/api/users"),
MetricLabel("zone", "ap-northeast"),

By labeling metrics, we can query in a more granular way in monitoring dashboards, such as

  • How many requests have been sent to each endpoint in total?
  • In which zone are we about to violate SLAs?
  • Which endpoint has the most latency?