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troubleshoot-varnish

Diagnose Varnish Cache failures using Netdata MCP metric queries.

1|Updated Apr 17, 2026
Search Tags:#troubleshooting#mcp#observability#varnish#resource exhaustion#operator playbook#cache hit ratio
One-click install
npx skills add https://github.com/netdata/skills --skill troubleshoot-varnish
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: troubleshoot-varnish
Source: https://github.com/netdata/skills/tree/main/skills/troubleshoot-varnish
Command: npx skills add https://github.com/netdata/skills --skill troubleshoot-varnish

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

Troubleshoot Varnish Cache performance and stability problems by identifying likely failure archetypes and confirming them with Netdata MCP metric queries.

Core Features & Use Cases

  • Failure-archetype diagnostic tree: Routes an investigation for thread pool exhaustion, cache stampede (thundering herd), ban list explosion, storage exhaustion, and workspace overflow.
  • Operator-playbook-aligned triage: Uses the same Netdata operator playbook signal domains to drive structured, evidence-based debugging.
  • MCP-based verification loop: Queries and validates Netdata varnish.* contexts (sessions/requests dropped, backend health, saturation/resources, cache hit ratio, thread management) to confirm whether remediation actually moved the signals.

Quick Start

Use the skill when you notice Varnish Cache behaving abnormally and want the agent to query Netdata via MCP, apply the diagnostic tree, and recommend targeted remediation: "Diagnose why our Varnish Cache is dropping sessions and requests, and tell me what to fix based on Netdata MCP metrics."

Frequently Asked Questions about troubleshoot-varnish

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I troubleshoot Varnish Cache dropping sessions and requests?▼

Varnish Cache thread pool exhaustion occurs when worker threads are saturated by high concurrency. Diagnose it by querying Netdata MCP varnish.* contexts for thread management and saturation signals to confirm the failure archetype and apply remediation.

What causes cache stampedes in Varnish and how can I diagnose them?▼

Cache stampedes in Varnish, or thundering herds, happen when expired cached objects trigger massive backend requests. Diagnose them using MCP queries to check cache hit ratio and backend health metrics within an operator-playbook triage framework.

Why is my Varnish ban list growing and causing performance issues?▼

A growing Varnish ban list degrades performance by consuming memory and increasing request processing overhead. Diagnose ban list explosion by querying varnish.* contexts via MCP to identify anomaly patterns and recommend cleanup actions.

Can I use Netdata MCP metrics to verify Varnish storage exhaustion fixes?▼

Yes, you can verify Varnish storage exhaustion fixes by re-running MCP queries for varnish.* contexts. Post-fix verification checks saturation and resource metrics to confirm remediation successfully moved the anomaly signals back to normal.

Does this diagnostic approach work for Varnish workspace overflow errors?▼

Yes, the diagnostic tree explicitly routes investigations for Varnish workspace overflow alongside storage depletion and thread pool issues. It uses rule-based triage ordering with MCP metric queries to confirm workspace overflow and recommend remediation.

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