Varnish High Availability
Varnish High Availability is a high-performance content replicator.
It is all about ensuring uptime for business-critical websites and applications and maximizing performance by aiming to eliminate cache misses and protect backend infrastructure from overload if the cache fails. The basic idea is: make sure your content is available and accessible 24/7 across a global distribution of servers.
To do this, Varnish High Availability turns pairs of Varnish Cache servers into ‘highly available’ caching clusters to ensure cached content remains available for your customers. As well as providing an extra layer of resilience, Varnish High Availability increases website performance through reduced cache misses. This also lowers the risk of backend traffic surges and page load time spikes, which are major speed bumps and leading causes of users’ losing interest and leaving the page or site.
Varnish High Availability features
- Cross-server content replication: Greater resilience and boosted performance for your backend setup. Performance is enhanced by cutting cache miss rates in half.
- Lightweight high-performance architecture: Requires minimal configuration and resources. The overhead from the replication stream is low, meaning that you get the benefits of more resilience and performance at a low cost.
- SSL/TLS support: Protected connections using TLS. All your data transfers can be encrypted, including those between data centers.
- Cluster support: VHA can replicate its cache to a potentially infinite number of nodes.
- Simpler VCL: All VHA in a replicated cluster can share the same configuration, making management easier and opening up the ability to use VHA in conjunction with Varnish Administration Console.
Automated VCL: VCL is now more consistent across nodes, and can be generated from cluster definition, which reduces human errors with more automation.
Bandwidth load reduction: VHA will now issue HEAD requests rather than GET requests, which effectively halves the network replication load.
Varnish High Availability benefits
- Increased resilience: reduced danger of sudden increases in miss rates, backend traffic surges and page load time spikes if a cache fails
- Simple configuration, stability: minimal business resources required
Who should use Varnish High Availability?
If your website or application is business critical - particularly large-scale enterprises - high availability is a no-brainer. High availability improves overall performance and protects costly origin servers. Fundamentally, high availability is all about scalability, reliability and guarding against outages while continuing to provide continuous service even in a failure. High availability functions as a first line of defense while also delivering performance enhancements and value in its everyday capacity of providing resilience.
Varnish High Availability has been designed for use with any multi-cache Varnish Cache setup, including two/three node CDN POP installations.
Find out more about how Varnish High Availability is being used by Surfline for real-time replication and load balancing.