file payload in google cloud function bucket triggered

Question

I have a question about a Google Cloud functions triggered by an event on a storage bucket (I’m developing it in Python).

I have to read the data of the file just finalized (a PDF file) on the bucket that is triggering the event and I was looking for the file payload on the event object passed to my function (data, context) but it seems there is not payload on that object.

Do I have to use the cloud storage library to get the file from the bucket ? Is there a way to get the payload directly from the context of the triggered function ?

Enrico

Frank van Puffelen Frank van Puffelen · Accepted Answer · 2020-05-31T20:39:17

From checking the more complete examplein the Firebase documentation, it indeed seems that the payload of the file is not included in the parameters. That make sense, since there's no telling how big the file is that was just finalized, and if that will even fit in the memory of your Functions runtime.

So you'll have to indeed grab the file from the bucket with a separate call, based on the information in the metadata. The full Firebase example grabs the filename and other info from its context/data with:

exports.generateThumbnail = functions.storage.object().onFinalize(async (object) => {
  const fileBucket = object.bucket; // The Storage bucket that contains the file.
  const filePath = object.name; // File path in the bucket.
  const contentType = object.contentType; // File content type.
  const metageneration = object.metageneration; // Number of times metadata has been generated. New objects have a value of 1.

  ...

I'll see if I can find a more complete example. But I'd expect it to work similarly on raw Google Cloud Functions, which Firebase wraps, even when using Python.

Update: from looking at this Storage/Function/PubSub documentation that the Python binding is apparently based on, it looks like the the path should be available as data['resource'] or as data['name'].

file payload in google cloud function bucket triggered

1 Answers