GCS - Python download blobs with directory structure

问题

I'm using a combination of the GCS python SDK and google API client to loop through a version-enabled bucket and download specific objects based on metadata.

from google.cloud import storage
from googleapiclient import discovery
from oauth2client.client import GoogleCredentials

def downloadepoch_objects():
    request = service.objects().list(
        bucket=bucket_name,
        versions=True
    )
    response = request.execute()

    for item in response['items']:
        if item['metadata']['epoch'] == restore_epoch:
            print(item['bucket'])
            print(item['name'])
            print(item['metadata']['epoch'])
            print(item['updated'])
            blob = source_bucket.blob(item['name'])
            blob.download_to_filename(
                '/Users/admin/git/data-processing/{}'.format(item))


downloadepoch_objects()

The above function works properly for a blob that is not within a directory (gs://bucketname/test1.txt) as the item that gets passed in is simply test1.txt. The issue I am running into is when trying to download files from a complex directory tree (gs://bucketname/nfs/media/docs/test1.txt) The item that gets passed is nfs/media/docs/test1.txt. Is it possible to have the .download_to_file() method to create directories if they are not present?

回答1:

GCS does not have a notion of "directories," although tools like gsutil do a good job of pretending for convenience. If you want all of the objects under the "nfs/media/docs/" path, you can specify that as a prefix, like so:

request = service.objects.list(
    bucket=bucket_name,
    versions=True,
    prefix='nfs/media/docs/',  # Only show objects beginning like this
    delimiter='/'  # Consider this character a directory marker.
)
response = request.execute()
subdirectories = response['prefixes']
objects = response['items']

Because of the prefix parameter, only objects that begin with 'nfs/media/docs' will be returned in response['items']. Because of the delimiter parameter, "subdirectories" will be returned in response['prefixes']. You can get more details in the Python documentation of the objects.list method.

If you were to use the newer google-cloud Python library, which I'd recommended for new code, the same call would look pretty similar:

from google.cloud import storage

client = storage.Client()
bucket = client.bucket(bucket_name)
iterator = bucket.list_blobs(
    versions=True,
    prefix='nfs/media/docs/',
    delimiter='/'
)
subdirectories = iterator.prefixes
objects = list(iterator)

回答2:

Below is the working solution. I ended up stripping away the path from the object name and creating the directory structure on the fly. A better way might be as @Brandon Yarbrough suggested using 'prefix + response['prefixes'][0]' but I couldn't quite figure that out. Hope this helps others out.

#!/usr/local/bin/python3

from google.cloud import storage
from googleapiclient import discovery
from oauth2client.client import GoogleCredentials
import json
import os
import pathlib

bucket_name = 'test-bucket'
restore_epoch = '1519189202'
restore_location = '/Users/admin/data/'

credentials = GoogleCredentials.get_application_default()
service = discovery.build('storage', 'v1', credentials=credentials)

storage_client = storage.Client()
source_bucket = storage_client.get_bucket(bucket_name)


def listall_objects():
    request = service.objects().list(
        bucket=bucket_name,
        versions=True
    )
    response = request.execute()
    print(json.dumps(response, indent=2))


def listname_objects():
    request = service.objects().list(
        bucket=bucket_name,
        versions=True
    )
    response = request.execute()

    for item in response['items']:
        print(item['name'] + ' Uploaded on: ' + item['updated'] +
              ' Epoch: ' + item['metadata']['epoch'])


def downloadepoch_objects():
    request = service.objects().list(
        bucket=bucket_name,
        versions=True
    )
    response = request.execute()

    try:
        for item in response['items']:
            if item['metadata']['epoch'] == restore_epoch:
                print('Downloading ' + item['name'] + ' from ' +
                      item['bucket'] + '; Epoch= ' + item['metadata']['epoch'])
                print('Saving to: ' + restore_location)
                blob = source_bucket.blob(item['name'])
                path = pathlib.Path(restore_location + r'{}'.format(item['name'])).parent
                if os.path.isdir(path):
                    blob.download_to_filename(restore_location + '{}'.format(item['name']))
                    print('Download complete')
                else:
                    os.mkdir(path)
                    blob.download_to_filename(restore_location + '{}'.format(item['name']))
                    print('Download complete')
    except Exception:
        pass


# listall_objects()
# listname_objects()
downloadepoch_objects()

来源：https://stackoverflow.com/questions/48449299/gcs-python-download-blobs-with-directory-structure