How to extract files in S3 on the fly with boto3? - amazon-web-services

Question

I'm trying to find a way to extract .gz files in S3 on the fly, that is no need to download it to locally, extract and then push it back to S3.
With boto3 + lambda, how can i achieve my goal?
I didn't see any extract part in boto3 document.

Answer 1

You can use BytesIO to stream the file from S3, run it through gzip, then pipe it back up to S3 using upload_fileobj to write the BytesIO.
# python imports
import boto3
from io import BytesIO
import gzip
# setup constants
bucket = '<bucket_name>'
gzipped_key = '<key_name.gz>'
uncompressed_key = '<key_name>'
# initialize s3 client, this is dependent upon your aws config being done
s3 = boto3.client('s3', use_ssl=False) # optional
s3.upload_fileobj( # upload a new obj to s3
Fileobj=gzip.GzipFile( # read in the output of gzip -d
None, # just return output as BytesIO
'rb', # read binary
fileobj=BytesIO(s3.get_object(Bucket=bucket, Key=gzipped_key)['Body'].read())),
Bucket=bucket, # target bucket, writing to
Key=uncompressed_key) # target key, writing to
Ensure that your key is reading in correctly:
# read the body of the s3 key object into a string to ensure download
s = s3.get_object(Bucket=bucket, Key=gzip_key)['Body'].read()
print(len(s)) # check to ensure some data was returned

Answer 2

The above answers are for gzip files, for zip files, you may try
import boto3
import zipfile
from io import BytesIO
bucket = 'bucket1'
s3 = boto3.client('s3', use_ssl=False)
Key_unzip = 'result_files/'
prefix = "folder_name/"
zipped_keys = s3.list_objects_v2(Bucket=bucket, Prefix=prefix, Delimiter = "/")
file_list = []
for key in zipped_keys['Contents']:
file_list.append(key['Key'])
#This will give you list of files in the folder you mentioned as prefix
s3_resource = boto3.resource('s3')
#Now create zip object one by one, this below is for 1st file in file_list
zip_obj = s3_resource.Object(bucket_name=bucket, key=file_list[0])
print (zip_obj)
buffer = BytesIO(zip_obj.get()["Body"].read())
z = zipfile.ZipFile(buffer)
for filename in z.namelist():
file_info = z.getinfo(filename)
s3_resource.meta.client.upload_fileobj(
z.open(filename),
Bucket=bucket,
Key='result_files/' + f'{filename}')
This will work for your zip file and your result unzipped data will be in result_files folder. Make sure to increase memory and time on AWS Lambda to maximum since some files are pretty large and needs time to write.

Answer 3

Amazon S3 is a storage service. There is no in-built capability to manipulate the content of files.
However, you could use an AWS Lambda function to retrieve an object from S3, decompress it, then upload content back up again. However, please note that there is default limit of 500MB in temporary disk space for Lambda, so avoid decompressing too much data at the same time.
You could configure the S3 bucket to trigger the Lambda function when a new file is created in the bucket. The Lambda function would then:
Use boto3 to download the new file
Use the gzip Python library to extract files
Use boto3 to upload the resulting file(s)
Sample code:
import gzip
import io
import boto3
bucket = '<bucket_name>'
key = '<key_name>'
s3 = boto3.client('s3', use_ssl=False)
compressed_file = io.BytesIO(
s3.get_object(Bucket=bucket, Key=key)['Body'].read())
uncompressed_file = gzip.GzipFile(None, 'rb', fileobj=compressed_file)
s3.upload_fileobj(Fileobj=uncompressed_file, Bucket=bucket, Key=key[:-3])