How can I view the contents of Varnish's hash_data()?

Question

I know that in Varnish you can add data to the cache hash using hash_data() within vcl_hash, as per the docs.

For debugging purposes, I would like to be able to see the entire contents of whatever is making up the hash.

For example, it would be really useful if we could do:

 # This won't work:
 set req.http.X-DEBUG = "HASH-DATA:" + hash_data();

Does anyone know if this is possible?

`varnishlog` properly explains what hash data is used for that specific request. Is that not sufficient - gathering the data from there? — Debreczeni András, Jul 17 '15 at 08:14
@debreczeni-andrás Yes that worked nicely for me, thanks. If you add this as an answer, I'll mark it as the accepted answer. — rangfu, Jul 20 '15 at 10:18

score 10 · Answer 1 · answered Dec 17 '17 at 22:31

10

You can usually see it with the varnishlog command.

However, since varnish 5 you need to enable the hash specifically in the log output. This can be done with the varnishadm utility:

Execute varnishadm and on the prompt it starts, type:

varnish> param.set vsl_mask +Hash

you can exit the shell by typing quit, and then run varnishlog again, it should display the hash used on each request now.

answered Dec 17 '17 at 22:31

ciencia

And in an oneliner: `sudo varnishadm param.set vsl_mask +Hash` – cherouvim Jan 15 '21 at 11:12

score 1 · Accepted Answer · answered Jul 20 '15 at 11:02

1

varnishlog properly explains what hash data is used for a specific request.

You can redirect the varnishlog output to your custom file for further review:

varnishlog > my-log.log

answered Jul 20 '15 at 11:02

4

This doesn't seem to be the case anymore with Varnish 5. Am I supposed to see Hash data with varnishlog because I don't see anything other than the VCL_call to HASH and the VCL_return hash. There is no tag named Hash available. – Yanick Girouard Jul 19 '17 at 19:16

2 Answers2