CDN Observability with Open Telemetry - Varnish + Oodle AI

This post explores what effective CDN observability looks like. It explains how Varnish, the content-delivery software trusted by Tesla, Walgreens, Emirates, Sky, etc., exposes telemetry through OpenTelemetry and why it built its standard dashboards on Oodle AI (see Varnish’s integration post).
It highlights key metrics, shows how they appear in dashboards, and describes how this integration simplifies observability for distributed CDN and edge environments.

The Challenge of Observability for CDNs

CDN observability isn’t just about tracking requests per second or cache hit ratios. At the edge, engineers deal with high concurrency, global latency variance, backend failures, and dynamic cache churn often all at once.

A small configuration change can shift terabytes of traffic or trigger cache invalidations across multiple points of presence. To manage that safely, you need visibility into every layer: client requests, cache behavior, backend fetches, queue lengths, and resource saturation.

How Varnish Enables Deep Observability by Design

Varnish’s architecture exposes detailed, structured data about its internal state. Its observability isn’t bolted on; it’s built in.

Here's why engineers value Varnish's Observability:

Sustained high-throughput performance: Handles hundreds of TBs of traffic daily with stable tail latency exposing queue depth, thread utilization, and cache efficiency so engineers can tune for consistent speed at scale.

Programmable edge control: Fully programmable caching and routing via VCL, with instant feedback through built-in metrics like backend latency, hit ratio, and invalidation frequency.

Bandwidth efficiency through visibility: Makes origin offload measurable. The detailed cache metrics let teams verify bandwidth savings and detect regressions as workloads change.

Hardware-level insight: Surfaces CPU and NIC counters that power 100 Gbps-class throughput, giving rare visibility into how hardware performance affects edge latency.

Hybrid and private-CDN readiness: Often used as an origin shield or private CDN tier; telemetry spans edge and origin for unified visibility across multi-CDN or hybrid setups.

Together, these characteristics make Varnish observability-ready without additional instrumentation.

From Varnish to OpenTelemetry

Varnish’s built-in tools: varnishstat, varnishlog, and extensions like vmod_accounting  provide deep insight into cache behavior. With the varnish-otel exporter, this data becomes portable and standardized. By emitting metrics, logs, and traces over OpenTelemetry, Varnish gives operators the freedom to choose their observability destination without lock-in or custom agents.

Oodle AI complements that perfectly by natively supporting OpenTelemetry ingestion. This makes observability easier to use, eliminates vendor lock-in, and lets engineers focus on improving their systems rather than managing tools.That flexibility is what makes the Oodle integration so straightforward: you can point varnish-otel at Oodle and start visualizing data immediately - as detailed in Brian Stewart’s blog post.

Why Oodle AI is a Natural Fit

Oodle AI is an AI-native observability platform designed for modern, high-cardinality telemetry, the exact kind of data Varnish generates at scale.It provides enterprise-grade performance at open-source cost, unifying metrics, logs, traces, and anomaly detection in one place.

Here’s why it fits CDN workloads particularly well:

1. Scales effortlessly across distributed caches and POPs without dropping tags or sampling data.
2. AI-native debugging correlates anomalies across metrics, logs and traces in one place. Ex: It can connect a latency spike with backend saturation or cache misses.
3. Familiar Grafana + OpenSearch UI lets engineers explore data instantly with no learning curve.
4. Fast setup: Connect in two commands and get pre-built dashboards in < 5min.

5× cost efficiency: Makes high-cardinality metrics and logs affordable and sustainable. (See pricing calculator) 

Standard Dashboards and Key Metrics

The varnish team created a standard dashboard organized around the five pillars most teams rely on. These sections help SREs and platform engineers focus on the metrics that actually move the needle balancing visibility with clarity.

• Overview: request throughput, cache hit ratio, backend health, panic indicators.
• Traffic: ESI subrequests, invalidations, pass ratio, origin requests.
• Saturation: thread utilization, queue depth, session drops.
• Errors: backend fetch failures, compression or ESI errors, sick backends.
• Latency: client, fetch, and delivery timings across cache layers.

For more details, check out this blogpost by Varnish.

Alerts: Turning Visibility into Action

Dashboards show you what’s happening; alerts make sure you know when it matters. Using Oodle’s native PromQL-based alerting, teams can define precise thresholds or anomaly rules for backend latency, cache efficiency, and error rates scoped by domain, POP, or backend label.

Example: Trigger an alert when avg_over_time(varnish_backend_req_time_seconds[5m]) > 0.5

Because Oodle is AI-native, related anomalies are automatically surfaced so when a latency spike occurs, Oodle can highlight linked metrics such as rising queue length or degraded cache hit ratio.This transforms alerting from simple thresholding into actionable diagnosis.Pro-tip: You can configure alerts through Terraform.[docs]

Trusted for CDN Observability

Oodle is now one of the trusted destinations for Varnish telemetry alongside Datadog, Grafana, Splunk, and New Relic giving CDN and edge operators flexibility without complexity.Our experience with Varnish’s data model and high-cardinality metrics ensures smooth ingestion, clean dashboards, and meaningful alerting from day one.

And for Oodle users exploring caching or edge acceleration, Varnish itself is worth a closer look, it’s one of the rare systems engineered with observability as a core principle.

Get Started in Minutes

Varnish users can explore a preconfigured dashboard and example alerts on Oodle’s playground, or follow the integration guide in Oodle’s documentation to connect varnish-otel.

You can reach us at support@oodle.ai.

Varnish Software is a global leader in high-performance caching and content delivery. Trusted by leading streaming services and enterprises worldwide, Varnish optimizes the delivery of digital content, APIs, and applications. Its customizable platform empowers businesses to scale efficiently, reduce costs, and deliver outstanding user experiences across video, web, and cloud environments.