Introduction

Varnish High Availability (VHA) is a content replicator for Varnish Enterprise. The latest version, Varnish High Availability 6, performs direct API-based cache-to-cache transfers without needing VCL context. VHA6 is available in the varnish-plus-ha package starting in Version 6.0.3r6.

For the legacy version of VHA, click here.

Architecture

VHA6 is an API-based content replication system. It requires no knowledge of the underlying user VCL. VHA6 works by broadcasting a replication request from an origin Varnish node to any number of Varnish peer nodes. The peers then fetch the object back from the origin node. All object attributes are exported from the origin and reimported on the peer.

The VHA6 replication API requires every request and object to be signed with a time-based HMAC-SHA256 signature. This signature is unique per object and secured against the configured VHA6 security token.

VHA6 Flow