[UI] "canceled - Unable to reach the management server" notification when switching from project to default view on Instances page (4.20.3) #14381

problem

After upgrading to 4.20.3.1, the UI shows an error notification every time I switch from a project view to the default view while the Instances page is open:

"canceled – Unable to reach the management server or a browser extension may be blocking the Network request."

This is not a network issue: nothing is logged in management-server.log at that moment, and the same error is shown when connecting to the management server directly (no reverse proxy). The instance list itself loads correctly after the switch.

The browser console shows that the in-flight listVirtualMachines request is intentionally cancelled by the UI on route change, and the resulting CanceledError is treated as a network failure and reported to the user:

AutogenView.vue:658 DEBUG - Due to route change, ignoring results for any on-going API request listVirtualMachines
CancelToken.js:58 Uncaught (in promise) i {message: 'canceled', name: 'CanceledError', code: 'ERR_CANCELED', ...}
cancel @ request.js:196
beforeRouteLeave @ AutogenView.vue:659
...
push @ vue-router.esm-bundler.js:2986
changeProject @ ProjectMenu.vue:92

versions

ACS: 4.20.3.1 (upgraded from [previous version])
Management servers: 3 nodes, Ubuntu 24.04, behind HAProxy (also reproducible when bypassing the proxy)
Browsers/OS: reproducible in multiple browsers and operating systems Chrome/Windows 11, Firefox/Ubuntu

The steps to reproduce the bug

1. Log in to the UI and select a project in the project selector.
2. Open Compute > Instances (the listing is shown for the project).
3. While on the Instances page, switch from the project view to the default view.
4. The error notification appears.

What to do about it?

The in-flight listVirtualMachines request is cancelled in beforeRouteLeave (AutogenView.vue) when the project is changed (changeProject in ProjectMenu.vue). The resulting CanceledError (ERR_CANCELED) is not filtered out and reaches the global error handler, which shows the "Unable to reach the management server..." notification.

A deliberately cancelled request should probably be silently ignored instead of being reported as a network error.