User information in Cloud functions via GCS triggers

Question

We are processing files automatically via Google cloud functions if any file is uploaded to Google cloud storage. We wrote the code using python.

https://cloud.google.com/functions/docs/calling/storage

def hello_gcs_generic(data, context):
    """Background Cloud Function to be triggered by Cloud Storage.
       This generic function logs relevant data when a file is changed.

    Args:
        data (dict): The Cloud Functions event payload.
        context (google.cloud.functions.Context): Metadata of triggering event.
    Returns:
        None; the output is written to Stackdriver Logging
    """

    print('Event ID: {}'.format(context.event_id))
    print('Event type: {}'.format(context.event_type))
    print('Bucket: {}'.format(data['bucket']))
    print('File: {}'.format(data['name']))
    print('Metageneration: {}'.format(data['metageneration']))
    print('Created: {}'.format(data['timeCreated']))
    print('Updated: {}'.format(data['updated']))

We want to know who uploaded the file for our logging purpose. I don't see any variable in data and context in the above function which provides user information.

Is there any way to find out who uploaded the file in GCF for GCS triggers?

marian.vladoi marian.vladoi · Accepted Answer · 2020-02-14T04:02:43

As you mentioned there is no variable for the owner of the object in data or context. However using the bucket name and the object name you can call Objects: get API which retrieves object metadata.

Using the projection full parameter you will receive the following response object:

{
  "kind": "storage#object",
  "id": string,
  "selfLink": string,
  "name": string,
  "bucket": string,
  "generation": long,
  "metageneration": long,
  "contentType": string,
  "timeCreated": datetime,
  "updated": datetime,
  "timeDeleted": datetime,
  "temporaryHold": boolean,
  "eventBasedHold": boolean,
  "retentionExpirationTime": datetime,
  "storageClass": string,
  "timeStorageClassUpdated": datetime,
  "size": unsigned long,
  "md5Hash": string,
  "mediaLink": string,
  "contentEncoding": string,
  "contentDisposition": string,
  "contentLanguage": string,
  "cacheControl": string,
  "metadata": {
    (key): string
  },
  "acl": [
    objectAccessControls Resource
  ],
  "owner": {
    "entity": string,
    "entityId": string
  },
  "crc32c": string,
  "componentCount": integer,
  "etag": string,
  "customerEncryption": {
    "encryptionAlgorithm": string,
    "keySha256": string
  },
  "kmsKeyName": string
}

Where owner is:

The owner of the object. This will always be the uploader of the object. If iamConfiguration.uniformBucketLevelAccess.enabled is set to true, this field does not apply, and is omitted in responses.

Google Cloud Storage Objects

I used the Api and the owner entity is the service account used to upload the file.

User information in Cloud functions via GCS triggers

2 Answers