[Bug]: Timeouts due to large number of synchronous requests by OnlyOffice

⚠️ This issue respects the following points: ⚠️

• This is a bug, not a question or a configuration/webserver/proxy issue.
• This issue is not already reported on Github OR Nextcloud Community Forum (I've searched it).
• Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
• I agree to follow Nextcloud's Code of Conduct.

Bug description

Nextcloud server ending up in timeouts (Error 504 Gateway Time-out) when OnlyOffice is requesting thumbnails. Already contacted OnlyOffice support who came to the following conclusion:

While working on the bug, we came to the conclusion that the solution needs to be deployed on the Nextcloud side and here is why:

The mechanism for converting thumbnails is implemented on the Nextcloud side and ONLYOFFICE works here as a tool by converting the thumbnail of the defined size from the exact file. Conversion requests are synchronised, Nextcloud triggers the method and waits for the result as a response.

The conversion request has a timeout of 2 minutes https://github.com/ONLYOFFICE/onlyoffice-nextcloud/blob/9da6d31f7d3b0610474890bbf89a5b65360fb8a6/lib/DocumentService.php#L172 The queue can be loaded and with a large number of requests the response time can reach the timeout time. Changing the timeout time will not solve the problem, so we cannot change the behaviour on our side.

It looks like handling a large number of synchronous requests should be implemented in the core of Nextcloud, as errors occur there due to overload.

Please contact the Nextcloud support team and describe the problem. If necessary, you can ask them to get in touch with us directly.

Steps to reproduce

1. Install OnlyOffice app and connect OnlyOffice server
2. Activate the document previews option under /settings/admin/onlyoffice

Expected behavior

OnlyOffice should properly generate document previews while Nextcloud is up and running.

Nextcloud Server version

30

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

Running a managed Nextcloud server hosted by Hetzner.

Start by reproducing the timeout with OnlyOffice document previews enabled under /settings/admin/onlyoffice, then review the linked OnlyOffice lib/DocumentService.php timeout behavior and the corresponding Nextcloud request path. The issue provides no Nextcloud file, test, logs, or configuration report, so the affected entry point and an appropriate regression test still need to be identified. Done means previews continue to generate without 504 timeouts under a large request load.