Bitbucket Data Center Mirror Page Stuck on "Loading add-on Mirror" Error

Platform Notice: Data Center Only - This article only applies to Atlassian products on the Data Center platform.

Note that this KB was created for the Data Center version of the product. Data Center KBs for non-Data-Center-specific features may also work for Server versions of the product, however they have not been tested. Support for Server* products ended on February 15th 2024. If you are running a Server product, you can visit the Atlassian Server end of support announcement to review your migration options.

*Except Fisheye and Crucible

Summary

In the Bitbucket Server administration panel a message is displayed saying "Loading add-on Mirror" indefinitely when performing one of these activities:

  • Trying to select which projects to mirror to a Bitbucket Smart Mirror:

    "Loading add-on Mirror" shows indefinitely when selecting which projects to mirror to a Bitbucket Smart Mirror.

  • Trying to access the Atlassian Troubleshooting and Support Tools for a Bitbucket Smart Mirror:

    "Loading add-on Mirror" shows indefinitely when accessing the Atlassian Troubleshooting and Support Tools for a Bitbucket Smart Mirror

Environment

The solution has been validated in Bitbucket Data Center 8.9.3 but may be applicable to other versions.

Diagnosis

No errors will be logged in the atlassian-bitbucket.log of either the mirror or the upstream node, indicating that this is not a server-side issue. However, when you inspect the network request in the browser, the following error will be logged.

  • Issue 1: While loading projects on the mirror page, the main GET request to the /plugins/servlet/admin/mirror endpoint will show a status of "blocked:other," even though the related request in the Bitbucket mirror log will be marked as successful.

    Network tab in browser's developer tools, the request to the /plugins/servlet/admin/mirror endpoint shows a status of "blocked:other"

  • Issue 2: While loading projects on the mirror page, the main GET request to the /plugins/servlet/admin/mirror endpoint will show a status of "(failed)net::ERR_CONNECTION_REFUSED", and the related request in the Bitbucket mirror log won't be seen.

    Network tab in browser's developer tools, the request to the /plugins/servlet/admin/mirror endpoint shows a status of "(failed)net::ERR_CONNECTION_REFUSED"

Cause

Cause 1:

The reverse proxy server is setting an HTTP response header that prevents the content rendered by the mirroring add-on from being displayed.

The user interface used to select which projects to synchronize to a Smart Mirror or to display the Atlassian Troubleshooting and Support Tools is embedded into the administration panel via an iframe. If the reverse proxy has been configured to send the X-Frame-Options header with the value SAMEORIGIN, the browser will not load any content embedded via iframes, and as a result the required user interface elements will not be displayed correctly.

For instance, Apache HTTP Server can be configured to behave in this way (i.e. set this header) with the following directive:

Header always append X-Frame-Options SAMEORIGIN

Cause 2:

The Bitbucket mirror isn’t accessible from the user's machine.

Solution

Resolution 1:

To resolve this problem, adjust the configuration of the load balancer so it no longer sets the X-Frame-Options header with SAMEORIGIN as its value.

Resolution 2:

Enable network connectivity from the user's machine to the Bitbucket mirror Base URL. After enabling the connection, verify it by accessing the Mirror URL from any browser.

Updated on June 30, 2025

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