[Bug]: PDF previews don't work after upgrade to 27 - Error 400

[Chartman123]

⚠️ 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

On one of my instances PDF previews do no longer work after upgrading to NC 27. On both my other instances it works as expected.

The failing one is using the official Docker images. The other two instances are classic installations at shared web hosters. Other differences: DB (pgsql <-> mariadb, redis <-> non redis)

PDF previews work with Imaginary disabled, so I think it's related to Imaginary.

Also, preview generation works for x >= 257 and y >= 257

Steps to reproduce

1. Browse to folder with PDF files
2. No previews, just the PDF logo

Expected behavior

See previews of files

Installation method

Community Docker image

Nextcloud Server version

27

Operating system

Other

PHP engine version

PHP 8.2

Web server

Apache (supported)

Database engine version

PostgreSQL

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

Upgraded to a MAJOR version (ex. 22 to 23)

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

{
    "system": {
        "htaccess.RewriteBase": "\/",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "apps_paths": [
            {
                "path": "\/var\/www\/html\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/var\/www\/html\/custom_apps",
                "url": "\/custom_apps",
                "writable": true
            }
        ],
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "cloud.tsmd.de"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "pgsql",
        "version": "27.0.0.8",
        "overwrite.cli.url": "https:\/\/cloud.tsmd.de",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "app_install_overwrite": [
            "occweb",
            "forms",
            "groupfolders",
            "announcementcenter",
            "metadata",
            "polls",
            "integration_whiteboard",
            "bruteforcesettings",
            "issuetemplate",
            "onlyoffice",
            "suspicious_login",
            "collectives",
            "impersonate",
            "approval"
        ],
        "maintenance": false,
        "loglevel": "2",
        "theme": "",
        "mail_smtpmode": "smtp",
        "mail_smtpsecure": "ssl",
        "mail_sendmailmode": "smtp",
        "mail_from_address": "***REMOVED SENSITIVE VALUE***",
        "mail_domain": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpauthtype": "LOGIN",
        "mail_smtpauth": 1,
        "mail_smtphost": "***REMOVED SENSITIVE VALUE***",
        "mail_smtpport": "465",
        "mail_smtpname": "***REMOVED SENSITIVE VALUE***",
        "mail_smtppassword": "***REMOVED SENSITIVE VALUE***",
        "forwarded_for_headers": [
            "X-Forwarded-For",
            "HTTP_X_FORWARDED_FOR"
        ],
        "overwritehost": "cloud.tsmd.de",
        "overwriteprotocol": "https",
        "default_language": "de",
        "default_locale": "de_DE",
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***",
        "skeletondirectory": "\/var\/www\/html\/data\/skeleton",
        "updater.release.channel": "stable",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 6379
        },
        "trashbin_retention_obligation": "auto,30",
        "versions_retention_obligation": "auto,30",
        "default_phone_region": "DE",
        "simpleSignUpLink.shown": false,
        "data-fingerprint": "681e3987b71dbcf8a80c491511dce9f8",
        "ldapProviderFactory": "OCA\\User_LDAP\\LDAPProviderFactory",
        "onlyoffice": {
            "jwt_header": "Jwt-Authorization"
        },
        "activity_use_cached_mountpoints": true,
        "enabledPreviewProviders": [
            "OC\\Preview\\PNG",
            "OC\\Preview\\JPEG",
            "OC\\Preview\\GIF",
            "OC\\Preview\\BMP",
            "OC\\Preview\\XBitmap",
            "OC\\Preview\\MP3",
            "OC\\Preview\\TXT",
            "OC\\Preview\\MarkDown",
            "OC\\Preview\\OpenDocument",
            "OC\\Preview\\Krita",
            "OC\\Preview\\Imaginary"
        ],
        "preview_imaginary_url": "http:\/\/imaginary:9000",
        "debug": false
    }
}

List of activated Apps

Enabled:
  - activity: 2.19.0
  - announcementcenter: 6.6.1
  - approval: 1.0.12
  - bruteforcesettings: 2.7.0
  - calendar: 4.4.2
  - circles: 27.0.0
  - cloud_federation_api: 1.10.0
  - collectives: 2.5.0
  - comments: 1.17.0
  - contacts: 5.3.1
  - dashboard: 7.7.0
  - dav: 1.27.0
  - deck: 1.10.0
  - federatedfilesharing: 1.17.0
  - federation: 1.17.0
  - files: 1.22.0
  - files_automatedtagging: 1.17.0
  - files_pdfviewer: 2.8.0
  - files_rightclick: 1.6.0
  - files_sharing: 1.19.0
  - files_trashbin: 1.17.0
  - files_versions: 1.20.0
  - firstrunwizard: 2.16.0
  - forms: 3.3.0
  - groupfolders: 15.0.0
  - impersonate: 1.14.0
  - integration_giphy: 1.0.6
  - integration_openstreetmap: 1.0.5
  - integration_whiteboard: 0.0.14
  - integration_youtube: 0.1.4
  - logreader: 2.12.0
  - lookup_server_connector: 1.15.0
  - mail: 3.2.2
  - nextcloud_announcements: 1.16.0
  - notifications: 2.15.0
  - notify_push: 0.6.3
  - oauth2: 1.15.0
  - onlyoffice: 8.1.0
  - password_policy: 1.17.0
  - polls: 5.0.5
  - privacy: 1.11.0
  - provisioning_api: 1.17.0
  - recommendations: 1.6.0
  - related_resources: 1.2.0
  - serverinfo: 1.17.0
  - settings: 1.9.0
  - sharebymail: 1.17.0
  - spreed: 17.0.0
  - survey_client: 1.15.0
  - suspicious_login: 5.0.0
  - systemtags: 1.17.0
  - tables: 0.5.1
  - text: 3.8.0
  - theming: 2.2.0
  - twofactor_backupcodes: 1.16.0
  - twofactor_nextcloud_notification: 3.7.0
  - twofactor_totp: 9.0.0
  - updatenotification: 1.17.0
  - user_ldap: 1.17.0
  - user_status: 1.7.0
  - viewer: 2.1.0
  - weather_status: 1.7.0
  - workflowengine: 2.9.0
Disabled:
  - admin_audit: 1.17.0
  - contactsinteraction: 1.8.0 (installed 1.7.0)
  - encryption: 2.15.0
  - files_external: 1.19.0
  - issuetemplate: 0.7.0 (installed 0.7.0)
  - libresign: 7.1.1 (installed 7.1.1)
  - photos: 2.3.0 (installed 1.0.0)
  - support: 1.10.0 (installed 1.1.0)

Nextcloud Signing status

No errors have been found.

Nextcloud Logs

Couldn't find anything in the logs, even with Debug mode

Additional info

https://cloud.domain.tld/core/preview?fileId=280976&c=bb75d279726eb8ef826eb9764852a2a1&x=250&y=250&forceIcon=0&a=1

Response code: 400
Response: []

[muchachagrande]

I'm having this issue but on a Hansson IT VM.
I can see that the preview is being generated because it is visible on the details panel of the file, but on the file list a PDF default icon is shown.

[muchachagrande]

I think that the problem is with the "preview" parameters "x" and "y".

When I enter a folder with PDFs Nextcloud tries to get a preview icon for each PDF.

The call is this:
GET /core/preview?fileId=3313142&c=628d0015278b2&x=250&y=250&forceIcon=0&a=1

If I test this call manually I get an empty json content-type.

But if I execute the call changing "x" and "y" for some bigger number like 512 x 512 or more I get the right icon with image/png content-type.

Also if you open the PDF detail view of the PDF it shows the correct preview image in the upper corner.
The call is different:
GET /core/preview?fileId=3313142&x=1920&y=1080&a=true

This call has x=1920 and y=1080 and it works fine.

[FarisZR]

I am also facing this issue with the official docker image.
Previews show up in the info panel, just not while browsing on the web or in apps, can confirm @muchachagrande analysis, just upping the size 512 fixes it.

I am using imaginary if that affects anything.

[Chartman123]

I just tried to find the numbers for x and y where the preview starts to work: its 257.

However, the image file in the response always has 793 x 793 pixels, regardless of the provided x and y values.

[JanisPlayer]

Yes, the previews of .HEIC files also do not load with the parameters &x=250&y=250&forceIcon=0&a=1.
.WebP also does not load without my PR changes to OC_Image.php.
This is likely because a different preview generator is being used for these files, not DG.
I was completely surprised by this bug and even reinstalled Nextcloud to then realize that the problem existed before.

[Chartman123]

At least for me this only happens with Imaginary enabled (see #40652 (comment))

[JanisPlayer]

At least for me this only happens with Imaginary enabled (see #40652 (comment))

Yes, I can confirm. Thank you for pointing me in the right direction. I checked my standard config again, and I forgot to remove "preview_imaginary_url" . Everything is working again now. Thanks, you've been a great help; I wouldn't have looked so closely otherwise.

[solracsf]

What are your Imaginary docker compose params?

[Chartman123]

@solracsf

  imaginary:
    image: nextcloud/aio-imaginary:latest
    deploy:
      update_config:
        order: start-first
    networks:
      - nextcloud

Just the basics. So the Entrypoint from the Dockerfile. I just added the other recommendations from your other post:

    entrypoint:
      - "imaginary"
      - "-return-size"
      - "-max-allowed-resolution"
      - "222.2"
      - "-concurrency" 
      - "50"
      - "-enable-url-source"
      - "log-level" 
      - "debug"
    cap_add:
      - sys_nice

I'm now testing it...

Edit:

No changes... As soon as I re-enable Imaginary in my config, the calls for the previews start to fail again with error code 400. In my debug output of the imaginary service, I don't see any requests.