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 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.
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.
At E2E, we monitor Varnish performance for CloudOps customers using Instana which collects the following
The excellent Varnish Book mentions several other uses for Varnish
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).