redmetrics

RED Metrics Examples

This directory contains OpenSLO examples for RED (Rate, Errors, Duration) metrics, a service-level monitoring methodology focused on request-driven services.

What are RED Metrics?

RED is a monitoring framework introduced by Tom Wilkie at Grafana Labs, designed specifically for monitoring request-driven services (APIs, microservices, web applications). The three pillars are:

• Rate: The number of requests per second your service is handling
• Errors: The number/percentage of those requests that are failing
• Duration: The amount of time those requests take (typically measured as latency percentiles)

Files in this Directory

rate.go

Measures the request rate (throughput) for an API service:

• ExampleRateSLO - Tracks requests per second to ensure the service handles expected traffic volume

error.go

Monitors the error rate of requests:

• ExampleErrorRateSLO - Tracks the ratio of successful responses (2xx, 3xx) vs errors (4xx, 5xx)

duration.go

Tracks request latency and response times:

• ExampleDurationSLO - Measures P95 latency to ensure fast response times
• ExampleDurationP99SLO - Measures P99 latency for tail latency monitoring

red_test.go

Validation tests for all RED metric SLOs

When to Use RED Metrics

RED metrics are ideal for:

• Request-driven services: REST APIs, GraphQL APIs, microservices
• Web applications: Backend services handling HTTP requests
• Service-to-service communication: Internal API calls
• User-facing endpoints: Any service where users make requests

Example Prometheus Queries

The examples use Prometheus as the metric source with queries like:

Rate:

rate(http_requests_total[5m])

Errors:

sum(rate(http_requests_total{status=~"2..|3.."}[5m])) / sum(rate(http_requests_total[5m]))

Duration:

histogram_quantile(0.95, rate(http_request_duration_seconds_bucket[5m]))

Complementary Frameworks

• USE Metrics: For infrastructure/resource monitoring (see ../use-metrics/)
• Four Golden Signals: Google's framework (similar to RED + Saturation)
• DORA Metrics: For measuring DevOps/deployment performance

References

• The RED Method - Tom Wilkie
• Monitoring Distributed Systems - Google SRE Book
• OpenSLO Specification: https://github.com/OpenSLO/OpenSLO