Removing cookies with vmod_cookie | All About

Did you know that the vmod_cookie is a Varnish Cache module?

It allows us to manipulate and modify cookies in incoming requests and outgoing responses. In other words, it lets us add, modify, or remove cookies from the request or response headers.

Furthermore, this enables us to implement different caching strategies and customize the behavior of our Varnish cache according to the cookie information.

Let’s take a quick look at how to use the vmod_cookie module to remove cookies from requests or responses in Varnish:

1. First, we have to install the vmod_cookie module.
2. Then. We have to head to the VCL configuration and load the module. This will make its functions available in our VCL code. This is usually done in the vcl_init subroutine:

   import cookie;

How to use vmod_cookie Functions

After we import the vmod_cookie module, we can use its functions to manipulate cookies as seen here:

• Removing Cookies:

  We can remove a specific cookie from incoming requests or outgoing responses with the cookie.remove function.

  For example, the following code in our VCL can remove a cookie named “session_id” from incoming requests:

  
sub vcl_recv {
cookie.remove(req.http.Cookie, "session_id");
}
• Removing Cookies from Responses:

  In case we want to prevent some cookies from being set in outgoing responses, we can use the cookie.remove function in the vcl_backend_response subroutine:

  
sub vcl_backend_response {
cookie.remove(beresp.http.Set-Cookie, "tracking_cookie");
}

Once we make changes to our VCL configuration with vmod_cookie, we have to test the configuration in a controlled environment before deploying it to production. Hence, we have to monitor the cache’s behavior and make sure the cookies are removed as intended.

Let us know in the comments if you need further help with removing cookies with vmod_cookie.

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Conclusion

In brief, our Support Techs demonstrated how to remove cookies with vmod_cookie.