Thumbor throws this error when trying to thumbnail this image. This bug exists on old (metal) and new (k8s) thumbor and was only caught due to the new logging.
2023-01-16 11:11:32,081 ???? thumbor:ERROR [BaseHander.finish_request] Failed to convert image b"convert: no images defined `png:-' @ error/convert.c/ConvertImageCommand/3258.\n"
Traceback (most recent call last):
File "/opt/lib/python/site-packages/thumbor/handlers/__init__.py", line 567, in finish_request
operation=functools.partial(self._load_results, context),
File "/opt/lib/python/site-packages/thumbor/threadpool.py", line 53, in queue
return await self._execute_in_foreground(operation, *args)
File "/opt/lib/python/site-packages/thumbor/threadpool.py", line 45, in _execute_in_foreground
return operation(*args)
File "/opt/lib/python/site-packages/thumbor/handlers/__init__.py", line 486, in _load_results
results = context.request.engine.read(image_extension, quality)
File "/srv/service/wikimedia_thumbor/engine/proxy/proxy.py", line 139, in read
ret = self.__getattr__('read')(extension, quality)
File "/srv/service/wikimedia_thumbor/engine/imagemagick/imagemagick.py", line 330, in read
raise ImageMagickException('Failed to convert image %s' % stderr) # pragma: no cover
wikimedia_thumbor.engine.imagemagick.imagemagick.ImageMagickException: Failed to convert image b"convert: no images defined `png:-' @ error/convert.c/ConvertImageCommand/3258.\n"
2023-01-16 11:11:32,090 ???? thumbor:WARNING Error while trying to fetch the image: Failed to convert image b"convert: no images defined `png:-' @ error/convert.c/ConvertImageCommand/3258.\n"Annoyingly we don't get the same command output here as in T327937, but this is a more complex case. Based on a reading of the code, this is the result of the thumbnail generation failing and then failing completely as opposed to partially. Worryingly we have found a case that this line references # Haven't been able to find a test file that meets this criteria.
It appears that this isn't related to our code itself but actually in the behaviour of convert as regards the file in question. The error seen above is what happens when insufficient arguments are given to convert, and the same can be seen here:
runuser@70658a454946:/tmp$ convert -resize 300 Earth_Impact_Database_world_map.svg # note missing argument here convert-im6.q16: no images defined `Earth_Impact_Database_world_map.svg' @ error/convert.c/ConvertImageCommand/3258. runuser@70658a454946:/tmp$ convert -resize 300 "UitlitéVsPénibilité-François-Dominique.png" abcd.png # sufficient arguments provided here, weird? convert-im6.q16: no images defined `abcd.png' @ error/convert.c/ConvertImageCommand/3258.
Note the reference to png:- is expected - this is us hoping to emit the image via stdout:
By default, the image format of `file' is determined by its magic number. To specify a particular image format, precede the filename with an image format name and a colon (i.e. ps:image) or specify the image type as the filename suffix (i.e. image.ps). Specify 'file' as '-' for standard input or output.