Error 503 Backend Fetch Failed: What It Means & How to Fix It

PDF download Download Article
Common solutions for the backend fetch failed error
PDF download Download Article

Are you getting the "Error 503 backend fetch failed" message when you try to access a website? This error, also known as the "Guru Meditation" error, is caused by the Varnish cache server and indicates a problem on the website or server's end. Read on to learn the meaning of error 503 and what you can do to fix it, whether you're the website owner or just browsing the web.

Error 503 Backend Fetch Failed: Fast Facts

If you come across error 503 when viewing a website, the server is having issues and can't fetch, or load, the website for you. If you're the website's owner, the error comes from the Varnish cache server and typically indicates a configuration issue.

Section 1 of 2:

What is Error 503?

PDF download Download Article
  1. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/5\/51\/Error-503-Backend-Fetch-Failed-Step-1-Version-2.jpg\/v4-460px-Error-503-Backend-Fetch-Failed-Step-1-Version-2.jpg","bigUrl":"\/images\/thumb\/5\/51\/Error-503-Backend-Fetch-Failed-Step-1-Version-2.jpg\/v4-728px-Error-503-Backend-Fetch-Failed-Step-1-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>License: <a target=\"_blank\" rel=\"nofollow noreferrer noopener\" class=\"external text\" href=\"https:\/\/en.wikipedia.org\/wiki\/Fair_use\">Fair Use<\/a> (screenshot)<br>\n<\/p><\/div>"}
    If you're browsing the web and come across this error, something is wrong with the website you're trying to view. This doesn't mean there's a problem with your computer, phone, browser, or internet connection, but you won't be able to access the website until its owner fixes it.
  2. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/c\/c3\/Error-503-Backend-Fetch-Failed-Step-2-Version-2.jpg\/v4-460px-Error-503-Backend-Fetch-Failed-Step-2-Version-2.jpg","bigUrl":"\/images\/thumb\/c\/c3\/Error-503-Backend-Fetch-Failed-Step-2-Version-2.jpg\/v4-728px-Error-503-Backend-Fetch-Failed-Step-2-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>License: <a target=\"_blank\" rel=\"nofollow noreferrer noopener\" class=\"external text\" href=\"https:\/\/en.wikipedia.org\/wiki\/Fair_use\">Fair Use<\/a> (screenshot)<br>\n<\/p><\/div>"}
    You may see this error when installing or using a plugin or module (such as for WordPress or Drupal) on your website and are using the Varnish cache server to improve your website speed. [1] The error means some aspect of your website is unable to retrieve needed data from another application, which can be due to:
    • The server the application is trying to connect to is unavailable. [2]
    • The IP address , hostname, or port for the web or application server is incorrect in your Varnish configuration file. [3]
    • The backend server is improperly defined in the relevant VCL file. [4]
    • Memory issues on the server.
    • Network problems between applications.
    3. Advertisement
Section 2 of 2:

How to Fix 503 Backend Fetch Failed

PDF download Download Article
  1. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/7\/74\/Error-503-Backend-Fetch-Failed-Step-3.jpg\/v4-460px-Error-503-Backend-Fetch-Failed-Step-3.jpg","bigUrl":"\/images\/thumb\/7\/74\/Error-503-Backend-Fetch-Failed-Step-3.jpg\/v4-728px-Error-503-Backend-Fetch-Failed-Step-3.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>License: <a target=\"_blank\" rel=\"nofollow noreferrer noopener\" class=\"external text\" href=\"https:\/\/en.wikipedia.org\/wiki\/Fair_use\">Fair Use<\/a> (screenshot)<br>\n<\/p><\/div>"}
    If you can't load a website because of error 503, the error is not on your end. To be extra sure, try going to a different website, such as wikihow.com or Google.com, and make sure you're not getting an error there. You can also try clearing your cache and cookies , though this will not usually fix error 503 backend fetch errors.
    • If you're supposed to be able to access the site, contact the admin to inform them of the error.
  2. {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/6\/64\/Error-503-Backend-Fetch-Failed-Step-4-Version-2.jpg\/v4-460px-Error-503-Backend-Fetch-Failed-Step-4-Version-2.jpg","bigUrl":"\/images\/thumb\/6\/64\/Error-503-Backend-Fetch-Failed-Step-4-Version-2.jpg\/v4-728px-Error-503-Backend-Fetch-Failed-Step-4-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><p>License: <a target=\"_blank\" rel=\"nofollow noreferrer noopener\" class=\"external text\" href=\"https:\/\/en.wikipedia.org\/wiki\/Fair_use\">Fair Use<\/a> (screenshot)<br>\n<\/p><\/div>"}
    The fix for error 503 depends on the cause, so you'll need to dig around in the logs to determine what prompted the error. Check your Varnish logs to assess the health of the backend server using the command sudo varnishlog -g raw -i backend_health .
    • If you cannot determine the cause of the error, run the command sudo varnishlog -g request -q "RespStatus == 503" to see which transactions resulted in the 503 backend fetch failed error. [5]
    • Depending on the application, plugin, or module you're using, you may need to make changes to the Varnish configuration file .
    3. Advertisement

Expert Q&A

Ask a Question
200 characters left
Include your email address to get a message when this question is answered.
Submit
      Advertisement

      Tips

      Submit a Tip
      All tip submissions are carefully reviewed before being published
      Name
      Please provide your name and last initial
      Submit
      Thanks for submitting a tip for review!

      You Might Also Like

      How to
      Clear Your Web Browser Cache on Any Platform
      How to
      Download Any Video for Free: 5 Step-by-Step Methods
      How to
      Allow Pop–ups
      How to
      Enable Cookies in Your Internet Web Browser
      How To Refresh a Webpage: Desktop & Mobile
      How to
      Turn on Cookies and JavaScript: Quick & Easy Guide
      Clear Your Web Browser Cache and Cookies on Any Platform
      How to
      Block Cookies in Chrome, Safari, & More
      3 Simple Ways to Make the Taskbar Transparent in Windows 10/11
      How to
      View Your Web Browser History
      How to
      Set a Specific Country in a Tor Browser
      8 Easy Ways to Fix reCAPTCHA Not Working in All Browsers
      Duplicate a Web Browser Tab in Chrome, Edge, + More
      How to
      Bookmark a Website in Any Browser
      Advertisement

      References

      1. ↑ https://www.drupal.org/forum/support/module-development-and-code-questions/2024-03-15/error-503-backend-fetch-failed-backend-fetch-failed-guru-meditation-varnish-cache-server
      2. ↑ https://stackoverflow.com/questions/70608310/varnish-503-backend-fetch-failed
      3. ↑ https://varnish-cache.org/docs/7.5/tutorial/starting_varnish.html
      4. ↑ https://varnish-cache.org/docs/7.4/users-guide/vcl-backends.html
      5. ↑ https://stackoverflow.com/questions/70608310/varnish-503-backend-fetch-failed

      About This Article

      Thanks to all authors for creating a page that has been read 756 times.

      Is this article up to date?

      Advertisement