Varnish modules (VMODs) are modules that extend the functionality of Varnish. Many VMODs work on their own to contribute a feature or benefit while others work in conjunction with external resources.
The newest VMODs in Varnish Plus, cookieplus and json, do a bit of both.
VMOD-cookieplus is a powerful cookie VMOD that supports manipulation of both client-side and server-side cookies (whereas the open source cookie VMOD allows only for client-side cookie handling). It is useful when integrating Varnish with cookie-intensive sites, in particular CMSes and e-commerce sites.
VMOD-cookieplus allows greater functionality and ease of use in complex cookie setups typical of large setups (CMSes and e-commerce sites) that employ extensive cookie use. It is designed to interact with request and response cookies and give you more granular control over cookie handling, for example letting you get, add, delete, and keep Cookie and Set-Cookie values. vmod-cookieplus also allows you to remove unused client-side cookies.
vmod-json brings the power of JSON to VCL. This module parses plain JSON strings from headers and can also parse JSON in request and response bodies and is a building block that contributes to creating more advanced functionality in Varnish.
A more in-depth explanation on a possible use for VMOD-json can be found in another recent blog post, Edge Logic: Securing Varnish with Per-User JSON data. It details how edge logic is key to achieving higher levels of performance, scale and security and how several Varnish Plus VMODs, including VMOD-json and VMOD-cookieplus (and VMOD-http), work together to let you create per-user security and access policies.
What do you think?
As always, as we continue to develop new VMODs and features, we welcome your input.
We invite you also to take a look at this brief overview of all the currently available Varnish VMODs.
If you'd like to get started with Varnish Plus and these VMODs, we invite you to sign up for a free trial.