Magento varnish 6 Too many restarts

Preconditions (*)

Magento 2.4-develop;
Production mode;
Sample Data;
Php 7.3;
Varnish v. 6.2

We tried 8823790#diff-2f64f6171deecba61bea147539cf72ec

However it results in too many restarts after a while.

Steps to reproduce (*)

1. Configure Varnish and Web server (Apache 2 in my case) devdocs;
2. Configure Magento to use Varnish

Go to Admin->Stores->Configuration->System->Full Page Cache:

• set Cache Application to Varnish Cache;
• set TTL for public content to 120 sec;
  

3. Export Varnish 6 VCL, configure and restart varnish service;
4. Run varnishlog in console;
5. Go to Storefront and try browsing the site for longer than 10min.

Use the VCL on production site with varnish 6.2, after a while certain objects get into a restart loop.

Expected result (*)

We expect no 503 errors caused by restart

Actual result (*)

✖️ VCL keeps restarting forever resulting in: - VCL_Error Too many restarts after a few tries
503 Response status and VCL error: Too many restarts

Varnish logs

[m2-assistant]

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

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• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

@magento give me 2.3-develop instance - upcoming 2.3.x release

For more details, please, review the Magento Contributor Assistant documentation.

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

• yes
• no

---

• Join Magento Community Engineering Slack and ask your questions in #github channel.

PS: We read the information here: https://varnish-cache.org/docs/6.2/whats-new/upgrading-6.2.html#whatsnew-upgrading-2019-03

and added in vcl_recv:

if (req.restarts > 0) { set req.hash_always_miss = true; }

Which improved the situation, although were not sure this is resolved properly & 100% supported

Update: We did further tests and it looks properly solved.

[ihor-sviziev]

Hi @HOSTED-POWER,
Thank you for report!

Could you add steps to reproduce to make sure that we'll be able to reproduce this issue?

That's really good that you already found solution for your issue. Could you create Pull Request with suggested fix?

Hello

To reproduce, install any Magento site (we had 2.3.1 and some 2.x versions) and wait for it to happen:

You can see the log like this:

varnishlog -q 'RespStatus == 503' -g request

Probably after a few minutes already you will see the 503 on certain objects and Varnish which goes into guru meditation error :)

We've seen it on all sites we tried it on, so it will be hard to not notice it.

To be on the safe side, we added this on top in vcl_recv:

sub vcl_recv {

    if (req.restarts > 0) {
        set req.hash_always_miss = true;
    }

    if (req.method == "PURGE") {
...

[hostep]

@Stepa4man: can you maybe also take a look at this to see if this proposed fix is ok?

HostedPower helped us solve this issue yesterday on one of our shops which is hosted with them, where we ran into unexplainable 503 Varnish errors. Their change seems to have fixed it 👍

[ihor-sviziev]

@engcom-Alfa @engcom-Bravo @engcom-Charlie,
Could you verify this issue?

[m2-assistant]

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[engcom-Delta]

Hi @HOSTED-POWER thank you for your report. I am not able to reproduce issue by steps you described on 2.3-develop.

If you'd like to update the issue, please reopen it.

Hello @engcom-Delta

Did you enable

varnishlog -q 'RespStatus == 503' -g request

And then crawled the whole site? Try that again after 30 min and again after 2 hours, it should really start happning :/

Used varnish 6.2 btw, not sure that would matter