503 backend fetch failed common bugfix does not work - path not applicable

Keywords: Magento - AWS - Technical issue - Other
Hi community,

I get the 503 Backend fetch failed error when I try to connect to my Magento backend that is hosted on a AWS Lightsail Instance - 2 GB RAM, 1 vCPU, 60 GB SSD. I found the general tutorial on how to fix it https://devdocs.magento.com/guides/v2.3/config-guide/varnish/tshoot-varnish-503.html, but the path described there does not exist on my instance.

However, I found another tutorial Error 503 Backend fetch failed Megenta after installation extension that states it would also work to take the path /opt/bitnami/varnish/scripts/ctl.sh (that applied to my configuration), open the file and add to the VARNISH_OPTIONS parameter string i.e. “-p http_resp_hdr_len=65536”. Still, I get the 503 Backend fetch failed error. This seems to be a common problem, I would appreciate any help with it!

I cannot even SSH into my console as the connectivity is so weak (or lost) that I cannot run the bitnami support tool.

Hi @maximilian.brueckner

We have a guide on how to configure and use Varnish at https://docs.bitnami.com/aws/apps/magento/administration/configure-use-varnish/ and a guide on troubleshooting Magento issues at https://docs.bitnami.com/aws/how-to/troubleshoot-magento-issues/. You can also try to check the Apache logs ot identify the source of the error, see https://docs.bitnami.com/aws/apps/magento/troubleshooting/debug-errors-apache/.

Could you have a look at these and see if they help?


Hi Vikram,

thank you for your quick reply!

I started three different versions of instances from Lightsail:

  • 512MB memory (3.50$/month)
  • 1GB memory (5$/month)
  • 2GB memory (10$/month)

I followed the general doc to start the Lightsail Instances and connect to the backend. For each instance, I was able to connect one time to the magento backend. After that, each instance slowed down until I could not even SSH into the console anymore.

I started a new instance with 2GB memory and tried to configure varnish https://docs.bitnami.com/aws/apps/magento/administration/configure-use-varnish/, but even when I disabled varnish and rebooted, the 503 backend fetch failed error appeared again.

I believe that many users must face this problem as I installed the lightsail instance as described in the bitnami docs. https://www.reddit.com/r/aws/comments/8mztfv/should_i_use_a_lightsail_instance_or_deploy_my/ Since more than one year there seems to be no stable fix for this issue.

We will configure an EC2 instance by ourself, as we spent several hours fixing this problem now.

However, I would be happy if you keep me updated about fixes, as (if it would work) Lightsail Magento with the Bitnami configuration would be a convenient and fast way to deliver shop systems to our customers.

Kind regards,


Hi @maximilian.brueckner

We have a Support Tool that will gather relevant information for us to analyze your configuration and logs. Could you please execute it on the machine where the stack is running by following the steps described in the guide below?

How to Run the Bitnami Support Tool

Please note that you need to paste the code ID that is shown at the end.



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