ghost
commented
10 years ago I've created something for this that could be included in the package. Just want your feedback before I refactor it into the cfs-storage-adapter.
How can the transformWrite function notify that an error has occured?
- The transformWrite function can throw an error that will be handled by the transformErrorHandler.
- The transformWrite function also receives a fourth argument. A function that can be called when an error occurs in transformWrite. Why?: Throwing errors inside event handlers (.on) doesn't do the right thing.
What will the error handler do?
- Save the error in file.copies[storageName].error. The frontend can check for this property and show the error to the user and/or delete the file for example.
- Emit an error on the writeStream, so the writeStream knows that it should abort.
- Unpipe the readStream. I don't know if this is necessary but it prevents further data transmission to the writeStream and the writeStream can handle the unpipe event.
- Emit the stored event (currently for compability)
Open
- @aldeed wrote
I think we want to ultimately funnel the error back up to an onError handler on the collection.(https://github.com/CollectionFS/Meteor-CollectionFS/issues/297#issuecomment-42769700).
My current transformErrorHandler code
/**
* Wrapper that handles errors that are thrown while transforming.
* It saves the error in the copy and emits stored.
* @param {string} storageName The name of the storage.
* @param {Function} transformFunction The transformation function.
* @returns {Function}
*/
var handleTransformErrors = function (storageName, transformFunction) {
return function (file, readStream, writeStream) {
var handleError = function (error) {
if (_.isObject(error) && error.errorType === 'Meteor.Error') {
error = _.pick(error, 'error', 'reason', 'details');
}
console.log('handleTransformError', error);
file.copies[storageName].error = error;
writeStream.emit('error', error);
readStream.unpipe(writeStream);
writeStream.emit('stored', {
fileKey: '',
size: 0,
storedAt: new Date()
});
};
try {
transformFunction(file, readStream, writeStream, handleError);
} catch (error) {
handleError(error);
}
};
};Usage
var eventPhotos = new FS.Store.S3('eventPhotos', {
// Options...
transformWrite: handleTransformErrors('eventPhotos', function (file, readStream, writeStream, handleError) {
// Transform code.
// Trigger error with throw:
throw new Meteor.Error(500, 'Transform failed');
// Or trigger error with callback:
handleError(new Meteor.Error(500, 'Transform failed');
})
});
aldeed
piyushcoader
cristiandley
RobertLowe
evolross
Issues like #225 are a bit hard to debug, there should be a better error message explaining that the Error toke place inside eg.
transformWriteand hand the error message and trace if available.