Varnish Cache Accelerator

 

Caching dynamic content is essential for any server receiving moderate to high traffic. The basic principle involves caching dynamic content periodically and offloading all requests to the high performance caching server.The same infrastructure is thus able to serve many times the number of requests a traditional web or application server would have otherwise.

 

Varnish Cache Accelerator - Functioning

Varnish cache Accelerator is a high-performance HTTP/web accelerator written in C programming language, to cache web content that maximizes cloud performance and reduce origin server load.

Reduced Response Time

Fulfill Requests

Load Balancing

CLI Tools

Acting as a reverse HTTP proxy, it stores cached content in memory to decrease the server response time and hence improves web page load times for visitors. Varnish’s Grace and Saint modes help to ensure graceful degradation by way of serving stale content if the backend server is unhealthy, down or throwing errors. Varnish can load balance between health-checked backends using roundrobin, fallback, random, hash and shard “directors” (load balancing algorithms). Varnish comes with a number of useful command line tools like varnishstat, varnishtop, varnishhist, varnishlog and varnishncsa.

 

 

User Experience Monitoring

At E2E, we monitor Varnish performance for CloudOps customers using Instana which collects the following

Metrics

  • Clients
  • Cache
  • Cached Objects
  • Threads
  • Backend

Health Signatures

  • Back-end Health
  • Hit Rate
  • Thread health and capacity
  • Thread creation

Benefits of Varnish

The excellent Varnish Book mentions several other uses for Varnish

  • Web application firewall
  • DDoS attack defender
  • Hotlinking protector
  • Integration point
  • Single sign-on gateway
  • Authentication and authorization policy mechanism
  • Quick fix for unstable backends
  • HTTP router

Our Varnish Appliance Plans on fast SSD storage come pre-installed with the enhanced varnish dashboard to view metrics, logs, stats, VCL and manage the varnish server (restart, update VCL, purge URLs, etc).