This error indicates that the website’s server could not communicate effectively with the back-end services. It is commonly triggered by updates to plugins, server OS, or extensions. Because it’s a server-side problem, clients can only attempt to refresh the website in their browsers.
Basic Troubleshooting
3. Check the Website Health and Resources
Insufficient storage or resources on a website can cause the backend fetch failed issue due to the inability to carry out necessary operations.
4. Check the Resource Availability
Attempting to access an absent resource on the backend server will result in an error message. Your reverse proxy might report this as a 503 backend fetch failed error.
5. Change the Cloudflare Settings
Suboptimal Cloudflare settings can cause an error 503 by restricting access to backend server resources. Changing these settings can rectify the issue.
6. Increase the Server Time-Out Limit
If the backend server’s response time is longer than what the reverse proxy is set to wait for (timeout), a backend fetch error will occur. Increasing the server’s time-out limit can address this problem. This may vary, but in Varnish, it can be done by:
7. Edit the Health Check Settings of the Website
The backend error may arise if the reverse proxy cache, like Varnish, is unable to access, or perceives the backend server health check information as faulty. The resolution is to repair the health check settings of the website:
8. Revert the PHP Version of the Server
If a recent PHP version upgrade is incompatible with your website’s backend, a 503 error may be triggered. Reverting to a prior PHP version can solve the issue. For example, on Bluehost with WordPress:
9. Disable Plugins, Utilities, Extensions, and Themes
When a plugin, utility, extension, or theme is incompatible with a server setup, a 503 error may result. Mitigate the error by disabling them and re-enabling one at a time to pinpoint the troublesome element. For instance, to disable GZip on the Jira Service Desk, which has been known to cause a 503 error:
10. Disable the CSP Module on Magento
The Content Security Policies (CSP) module provides security for Magento applications. If the CSP module is incompatible with your current setup, it can trigger a 503 error. Disabling the CSP Module on Magento could solve the issue:
11. Change Host Header, Child Tag, and Port Configurations
Backend fetch errors can also stem from overly large host headers, improperly configured child tags, or incorrect port configurations. Editing these settings might rectify the error.
Add a .host_header Property
Remove Child Tags from Magento
Remove Ports from the Docker Compose
12. Use a Systematic Approach
If all previous steps have failed, a systematic approach should be employed to isolate the cause of the error 503.
Check Logs
Do a Full Conflict Test
Perform a full conflict test if your setup permits, to discover any potential conflicts. If any conflicts arise, resolve them to clear the backend fetch error.
Directly Access the Backend Server
If you are utilizing a reverse proxy like Varnish, bypass it and try directly accessing the backend server. If this method works, the issue likely lies with the reverse proxy setup. Consider the following steps if direct access is successful: If these methods are ineffective, strip down the website to its most fundamental elements, such as an index file with some placeholder content. Gradually reintroduce features to determine which one triggers the error 503. If the problem continues, reach out to the appropriate support channels for assistance, be it WordPress Support, Magento Support, or the hosting provider’s customer service team, such as Hostinger Support.
