Magento2: Varnish VCL - bin/magento varnish:vcl:generate command generates vcl with deprecated value

[shkoliar]

Preconditions (*)

1. PHP 7.2, MariaDB 10.3, Varnish 5.2.1
2. Tested with Magento 2.3.2 and Magento 2.3.1

Steps to reproduce (*)

1. Run command
   bash bin/magento varnish:vcl:generate --access-list localhost --backend-host localhost --backend-port 8080 --output-file var/default.vcl
2. Run commands
   bash varnishadm vcl.load default var/default.vcl varnishadm vcl.use default

Expected result (*)

1. Contents of generated var/default.vcl file, pay attention to correct row return (miss);
   ````
   ...

sub vcl_hit {
if (obj.ttl >= 0s) {
# Hit within TTL period
return (deliver);
}
if (std.healthy(req.backend_hint)) {
if (obj.ttl + 300s > 0s) {
# Hit after TTL expiration, but within grace period
set req.http.grace = "normal (healthy server)";
return (deliver);
} else {
# Hit after TTL and grace expiration
return (miss);
}
} else {
# server is not healthy, retrieve from cache
set req.http.grace = "unlimited (unhealthy server)";
return (deliver);
}
}
````

1. Varnish varnishadm command loads and activates config.

Actual result (*)

1. Contents of generated var/default.vcl file, pay attention to deprecated return (fetch);
   ````
   ...

sub vcl_hit {
if (obj.ttl >= 0s) {
# Hit within TTL period
return (deliver);
}
if (std.healthy(req.backend_hint)) {
if (obj.ttl + 300s > 0s) {
# Hit after TTL expiration, but within grace period
set req.http.grace = "normal (healthy server)";
return (deliver);
} else {
# Hit after TTL and grace expiration
return (fetch);
}
} else {
# server is not healthy, retrieve from cache
set req.http.grace = "unlimited (unhealthy server)";
return (deliver);
}
}
````

1. Varnish varnishadm commands results with error
   ````
   Message from VCC-compiler:
   Invalid return "fetch"
   ...
   return (fetch);
   --------------------#####--

...in subroutine "vcl_hit"
...
sub vcl_hit {
----#######--

...which is the "vcl_hit" method
Legal returns are: "deliver" "fail" "miss" "pass" "restart" "synth"
Running VCC-compiler failed, exited with 2
VCL compilation failed
Command failed with error code 106
````

[m2-assistant[bot]]

Hi @shkoliar. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• [ ] Summary of the issue
• [ ] Information on your environment
• [ ] Steps to reproduce
• [ ] Expected and actual results

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@shkoliar do you confirm that you were able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• [ ] yes
• [ ] no

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[shkoliar]

FYI, varnish VCL config generated from Magento admin panel has correct values. The issue is related only to bin/magento varnish:vcl:generate command.

[m2-assistant[bot]]

Hi @engcom-Bravo. Thank you for working on this issue.
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[engcom-Bravo]

@magento give me 2.2-develop instance

[magento-engcom-team]

Hi @engcom-Bravo. Thank you for your request. I'm working on Magento 2.2-develop instance for you

[magento-engcom-team]

Hi @engcom-Bravo, here is your Magento instance.
Admin access: https://i-23670-2-2-develop.instances.magento-community.engineering/admin
Login: admin Password: 123123q
Instance will be terminated in up to 3 hours.

[magento-engcom-team]

:white_check_mark: Confirmed by @engcom-Bravo
Thank you for verifying the issue. Based on the provided information internal tickets MC-18131, MC-18132 were created

Issue Available: @engcom-Bravo, _You will be automatically unassigned. Contributors/Maintainers can claim this issue to continue. To reclaim and continue work, reassign the ticket to yourself._

[shkoliar]

After digging in the source code for bin/magento varnish:vcl:generate cli command, I've found out that command line parameter --export-version responsible for vcl version output.

To sum up, --export-version parameter, when omitted, defaults to Varnish 4, and to get vcl config for Varnish 5 we need to include that parameter with corresponding version value.

It would be good to add more information about varnish:vcl:generate command to dev docs.

[shkoliar]

Dev docs have a note about actual command and its parameters, but no detailed description and defaults like for other commands.

https://devdocs.magento.com/guides/v2.2/reference/cli/magento.html
https://devdocs.magento.com/guides/v2.3/reference/cli/magento.html

[pniel-cohen]

FYI: I managed to reproduce the issue on Magento 2.3.2 when I exported the vcl file from the admin panel (Varnish 4). Solved it manually by editing the file & replacing the fetch with miss on sub vcl_hit{...}.