TypeError is thrown in preview generator

[nielstron]

2024-09-09T20:48:53+00:00 Scanning folder /anonymized/path
An unhandled exception has been thrown:
TypeError: stream_get_contents(): Argument #1 ($stream) must be of type resource, false given in /var/www/html/lib/private/Preview/ProviderV2.php:93
Stack trace:
#0 /var/www/html/lib/private/Preview/ProviderV2.php(93): stream_get_contents()
#1 /var/www/html/lib/private/Preview/Movie.php(99): OC\Preview\ProviderV2->getLocalFile()
#2 /var/www/html/lib/private/Preview/GeneratorHelper.php(64): OC\Preview\Movie->getThumbnail()
#3 /var/www/html/lib/private/Preview/Generator.php(361): OC\Preview\GeneratorHelper->getThumbnail()
#4 /var/www/html/lib/private/Preview/Generator.php(337): OC\Preview\Generator->generateProviderPreview()
#5 /var/www/html/lib/private/Preview/Generator.php(143): OC\Preview\Generator->getMaxPreview()
#6 /var/www/html/lib/private/PreviewManager.php(211): OC\Preview\Generator->generatePreviews()
#7 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(232): OC\PreviewManager->generatePreviews()
#8 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(214): OCA\PreviewGenerator\Command\Generate->parseFile()
#9 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(212): OCA\PreviewGenerator\Command\Generate->parseFolder()
#10 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(212): OCA\PreviewGenerator\Command\Generate->parseFolder()
#11 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(212): OCA\PreviewGenerator\Command\Generate->parseFolder()
#12 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(212): OCA\PreviewGenerator\Command\Generate->parseFolder()
#13 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(212): OCA\PreviewGenerator\Command\Generate->parseFolder()
#14 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(192): OCA\PreviewGenerator\Command\Generate->parseFolder()
#15 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(138): OCA\PreviewGenerator\Command\Generate->generateUserPreviews()
#16 /var/www/html/lib/private/User/Manager.php(666): OCA\PreviewGenerator\Command\Generate->OCA\PreviewGenerator\Command\{closure}()
#17 /var/www/html/apps/previewgenerator/lib/Command/Generate.php(137): OC\User\Manager->callForSeenUsers()
#18 /var/www/html/3rdparty/symfony/console/Command/Command.php(298): OCA\PreviewGenerator\Command\Generate->execute()
#19 /var/www/html/3rdparty/symfony/console/Application.php(1040): Symfony\Component\Console\Command\Command->run()
#20 /var/www/html/3rdparty/symfony/console/Application.php(301): Symfony\Component\Console\Application->doRunCommand()
#21 /var/www/html/3rdparty/symfony/console/Application.php(171): Symfony\Component\Console\Application->doRun()
#22 /var/www/html/lib/private/Console/Application.php(213): Symfony\Component\Console\Application->run()
#23 /var/www/html/console.php(102): OC\Console\Application->run()
#24 /var/www/html/occ(11): require_once('...')

Already occured several times, trying to generate previews for all files.

Nextcloud: Nextcloud Hub 8 (29.0.6)
Preview generator: 5.6.0

[st3iny]

I think I found the problematic piece of code.

@nielstron Could you please share some more information on the problematic file?

1. Does the error occur on the same file over and over again?
2. Is the file on local storage, S3 primary storage or an external storage?
3. Is the file accessible via e.g. the web interface (in a sense: is it corrupted)?

[nielstron]

1. The error occurs sporadically, on different files
2. The file is on external storage (SFTP)
3. I can not check this point because this file belongs to a user. Its very possible that the file(s) is/are corrupted

[st3iny]

Ok, thanks for the info.

So it seems that the underlying issue is probably caused by a flaky connection to the SFTP server. Hence the call to fopen fails.

I'll create a PR to handle this case gracefully.