Different behavior of varnishd -C in varnish 5

[mookie-]

Expected Behavior

If I run varnishd -C -f /etc/varnish/varnish.vcl -a 127.0.0.1:80 [...] varnishd should ignored the other options except "-C -f"

Current Behavior

On varnishd <5 it works. On varnishd >5 I get Error: Could not get socket 127.0.0.1:80: Address already in use

Possible Solution

Make it like before or note it in the changes/upgrade documentation.

Steps to Reproduce (for bugs)

1. Start varnishd with -a $ip:$port
2. execute varnishd -C -f /etc/varnish/varnish.vcl -a $ip:$port
3. get Error: Could not get socket $ip:$port: Address already in use

Context

varnishd -C -f $all_other_varnish_options is used as configuration check in (some/many) init scripts.
Did work at least for varnish 3 and 4.

Your Environment

• Version used: 5.1.2
• Operating System and version: Gentoo
• Source of binary packages used (if any): used source from http://repo.varnish-cache.org/source/varnish-5.1.2.tar.gz

[nigoroll]

Ref #2141 #2217

[nigoroll]

@bsdphk I'm tempted to leave this with you due to your work on #2141.At first sight I'd think we need to pull the VSS_resolver() call out of MAC_Arg()

[mookie-]

Something to add. Probably not all other options should be ignored. If you e.g. specify vcl_path with varnishd -p vcl_path=[...] this option is needed for -C. It's probably enough to just ignore the -as.

[nigoroll]

Thanks @mookie-. That should be clear and was already discussed. See the other issues I referenced.

[denisbr]

Is there any update on this? Will this be fixed in next release?

[dridi]

This is a more complex problem than it looks, I'll try to summarize it here:

Some of the symbols available in VCL depend on the varnishd command line. Currently only the storage.<name> variables named after -s options, and in the future possibly new symbols for the -a options.

Those options are needed on the varnishd -C command line, so that for example -s small=malloc gives you a proper storage.small symbol in VCL and the associated storage.small.* variables (see man vcl).

One possibility we discussed was to ignore the options, and even allow to omit them. The -C mode would assume any storage to be valid. The flip side is that typos like storage.smalll would pass unnoticed.

So the next solution would be to require the same command line, but in -C mode this option would need to be the very first one (like -x when used) and the other options would avoid side effects outside of the working directory (eg. binding sockets, creating storage files etc).

I believe this is what we are supposed to do, but at this point I don't know our progress. I may have missed further discussions during the holidays season but to my knowledge this hasn't been discussed in a while. Current master doesn't enforce -C to be the first parameter when used.

[denisbr]

After @dridi explained the nitty gritty details, we agreed that if varnishd -C still doesn't work if there is a running varnishd, when the release is cut, we'll just put the "configtest before restart" logic on ice for now. It's better to have packages with a working restart than insisting on keeping this logic around (when it doesn't really work).

[bsdphk]

I am going to kill this ticket, because what is being asked for is patently not possible in general and would lead to tons and tons of ugly workarounds.

It would for instance be easy to add "pretend" code to -a arguments, but it would be wrong, because only by binding the socket do we actually get its IP and port number in the weird corner cases of FreeBSD-jails or :0

-C is for test-compiling VCL code (and seeing the resulting C source) it is not a flag for testing the rest of the arguments.