Issues during size scaling of images (mostly occurs with jpeg)

[hyatt03]

I have a hard time describing the issue, so I've attached an example instead:

As you can see, it seems an issue occurs while scaling jpeg images, however it's not a consistent issue, and libvips throws warnings when it happens. For example

vips warning: VipsJpeg: read gave 2 warnings
vips warning:
Assertion failed: (loop->watchers[w->fd] == w), function uv__io_stop, file ../deps/uv/src/unix/core.c, line 864.
Program node main.js exited with code null

If I can listen for these warnings, that would be sufficient.
Here is the original image:

It seems to occur in about 0.6% of scaling jobs, for reference here is the code I use to scale the image (edited for brevity):

let imageObject = sharp(fileobj.name);
        imageObject.metadata().then((metadata) => {
          if (metadata.orientation) {
            imageObject.rotate();
          }

          return imageObject;
        }).then((image) => {
          imageObject = image;

          if (width && height) {
            imageObject.resize(width, height).withoutEnlargement();
          }
          else {
            imageObject.resize(width).max().withoutEnlargement();
          }

          imageObject.toBuffer()
            .then(function (outputBuffer) {
              logger.info('finished image transcoding job', {
                    size: width && height ? `${width}x${height}` : `${width}x${width}`,
                    data: job.data
                  });
                }
              );
            })
            .catch(function (err) {
              done();
              logger.error('an error occurred while transcoding image', {job: job.data, error: err});
            });
        }).catch((err) => {
          done();
          logger.error('an error occurred while transcoding image', {job: job.data, error: err});
        });

[lovell]

"Assertion failed: (loop->watchers[w->fd] == w), function uv__io_stop, file ../deps/uv/src/unix/core.c, line 864."

Hello, this is an error I've not seen before.

The vips warning messages and the truncated JPEG suggest there might have been an unclean thread shutdown, possibly based on a fatal error in another thread.

Could main.js be dependent on any other modules that deal with file watching or hot-reloading? Are you able to share a list of the other (native) modules upon which it depends?

[lovell]

There are quite a few other modules with similar reports for this problem https://github.com/search?o=desc&q=Assertion+failed%3A+%28loop-%3Ewatchers%5Bw-%3Efd%5D+%3D%3D+w%29%2C+function+uv__io_stop&s=created&type=Issues&utf8=%E2%9C%93

[lovell]

If this is caused by libvips writing to stderr (rather than that being a side-effect of another problem) then nodejs/node#3422 looks relevant with mscdex/node-mariasql@f777a0e being the fix referred to.

sharp doesn't directly use any of libuv's file handling logic so my best guess remains that another module is doing so - if not MariaDB then perhaps a logging or monitoring library that's trying to watch stderr.

[hyatt03]

Thank you for the response!

I've looked at our logs, and it turns out the assertion error doesn't always happen in conjunction with a read error, in fact, most of the time the read error happens with an assertion error.

The process continues nontheless, without reporting an error, and that's our primary concern.

[lovell]

Are you able to set the VIPS_WARNING=0 environment variable to silence these warnings? This will (temporarily, at least) help separate what might be two different problems interfering with each other.

[lovell]

Were you able to solve this? If so, are you able to share details in case others have the same problem? Thanks!

[hyatt03]

Thank you for trying to help me. I was not able to solve it, and I had to replace the library as it caused a sigabort (I think libvips -> imagemagick), which crashed my application (forever detected the sigabort and killed the process). If I get the time to look into the cause, I will, but for now I must leave you without an answer.