Connect SFTP to Google Cloud Storage
Setup in 15 minutes with code or no code!
Video instructions below.

import os
import paramiko
import io
import pandas as pd
import stat
from google.cloud import storage, secretmanager
from flask import jsonify
from datetime import datetime
from dotenv import load_dotenv
import logging

# Load environment variables from .env file
load_dotenv()

# Setup logging
logging.basicConfig(level=logging.DEBUG)

def get_secret(secret_id):
logging.debug(f”Retrieving secret for secret_id: {secret_id}”)
try:
client = secretmanager.SecretManagerServiceClient()
project_id = os.getenv(“GOOGLE_CLOUD_PROJECT”)
logging.debug(f”Project ID: {project_id}”)

secret_name = f”projects/{project_id}/secrets/{secret_id}/versions/latest”
logging.debug(f”Secret name: {secret_name}”)

response = client.access_secret_version(request={“name”: secret_name})
logging.debug(f”Secret response received: {response}”)

secret_value = response.payload.data
logging.debug(f”Secret value (raw): {secret_value}”)

if isinstance(secret_value, bytes):
secret_value = secret_value.decode(‘utf-8’)
logging.debug(f”Secret value decoded: {secret_value}”)
return secret_value
except Exception as e:
logging.error(f”Error retrieving secret {secret_id}: {e}”)
return None

def normalize_private_key(private_key):
logging.debug(“Normalizing private key”)
lines = private_key.strip().split(“\\n”)
normalized_key = “\n”.join(lines)
logging.debug(f”Normalized private key: {normalized_key}”)
return normalized_key

def create_sftp_connection(host, username, private_key_pem):
logging.debug(f”Creating SFTP connection to host: {host} with username: {username}”)
try:
ssh_client = paramiko.SSHClient()
ssh_client.load_system_host_keys()
ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())

if private_key_pem is None:
raise ValueError(“The private key is None. Check the secret retrieval.”)

logging.debug(f”Private key PEM type: {type(private_key_pem)}”)
private_key_pem = normalize_private_key(private_key_pem)
if isinstance(private_key_pem, str):
private_key_bytes = private_key_pem.encode(‘utf-8’)
else:
private_key_bytes = private_key_pem

logging.debug(f”Keyfile type: {type(private_key_bytes)}, length: {len(private_key_bytes)}”)

private_key_file = io.StringIO(private_key_pem)
private_key = paramiko.RSAKey.from_private_key(private_key_file)
logging.debug(“Private key loaded successfully”)

logging.debug(f”Attempting to connect to SFTP server {host} as {username}”)
ssh_client.connect(host, username=username, pkey=private_key, banner_timeout=200)
sftp_client = ssh_client.open_sftp()
logging.debug(‘SFTP Connection Successful’)

return sftp_client, ssh_client
except paramiko.ssh_exception.SSHException as e:
logging.error(f”SSHException creating SFTP connection: {e}”)
except Exception as e:
logging.error(f”Error creating SFTP connection: {e}”)
return None, None

def retrieve_sftp_files(sftp_client, base_directory, relative_path=”, file_details=None):
logging.debug(f”Retrieving SFTP files from base_directory: {base_directory}, relative_path: {relative_path}”)
if file_details is None:
file_details = []

current_directory = os.path.join(base_directory, relative_path)
logging.debug(f”Current directory: {current_directory}”)

try:
for entry in sftp_client.listdir_attr(current_directory):
logging.debug(f”Entry: {entry.filename}, is directory: {stat.S_ISDIR(entry.st_mode)}”)
if stat.S_ISDIR(entry.st_mode): # if folder
new_path = os.path.join(relative_path, entry.filename)
retrieve_sftp_files(sftp_client, base_directory, new_path, file_details)
else: # if file
filename = entry.filename
filepath = os.path.join(relative_path, filename)
last_modified = datetime.fromtimestamp(entry.st_mtime)
days_since_modified = (datetime.now() – last_modified).days
file_details.append({‘filename’: filename, ‘filepath’: filepath, ‘days_since_modified’: days_since_modified})
logging.debug(f”File: {filename}, Path: {filepath}, Days since modified: {days_since_modified}”)

logging.info(f”Retrieved {len(file_details)} file details.”)
except Exception as e:
logging.error(f”Error retrieving SFTP files: {e}”)

return file_details

def fetch_file(sftp_client, remote_filepath, local_filepath):
logging.debug(f”Fetching file from remote_filepath: {remote_filepath} to local_filepath: {local_filepath}”)
try:
sftp_client.get(remote_filepath, local_filepath)
logging.info(f”Fetched file from {remote_filepath} to {local_filepath}.”)
except Exception as e:
logging.error(f”Error fetching file {remote_filepath}: {e}”)

def transfer_to_gcs(bucket_name, local_filepath, remote_blob_name):
logging.debug(f”Transferring file to GCS bucket: {bucket_name}, local_filepath: {local_filepath}, remote_blob_name: {remote_blob_name}”)
try:
storage_client = storage.Client()
bucket = storage_client.bucket(bucket_name)
blob = bucket.blob(remote_blob_name)
blob.upload_from_filename(local_filepath)
logging.info(f”Transferred file {local_filepath} to GCS bucket {bucket_name} as {remote_blob_name}.”)
except Exception as e:
logging.error(f”Error transferring file to GCS: {e}”)

def identify_new_files(sftp_client, base_directory, days_threshold):
logging.debug(f”Identifying new files in base_directory: {base_directory} with days_threshold: {days_threshold}”)
try:
sftp_files = retrieve_sftp_files(sftp_client=sftp_client, base_directory=base_directory, relative_path=”, file_details=None)
sftp_files_df = pd.DataFrame(sftp_files)
logging.debug(f”SFTP files dataframe: {sftp_files_df}”)

if days_threshold:
sftp_files_df = sftp_files_df[sftp_files_df[‘days_since_modified’] <= days_threshold]

bucket_name = os.getenv(“GCS_BUCKET_NAME”)
storage_client = storage.Client()
bucket = storage_client.bucket(bucket_name)

blobs = bucket.list_blobs()
gcs_files = [(blob.name.split(‘/’)[-1], blob.name) for blob in blobs]
gcs_files_df = pd.DataFrame(gcs_files, columns=[‘gcs_filename’, ‘gcs_filepath’])
logging.debug(f”GCS files dataframe: {gcs_files_df}”)

merged_df = sftp_files_df.merge(gcs_files_df, how=’left’, left_on=[‘filepath’], right_on=[‘gcs_filepath’])
merged_df = merged_df[merged_df[‘gcs_filepath’].isna()]
merged_df.sort_values(by=’days_since_modified’, inplace=True, ascending=True)

logging.info(f”Identified {len(merged_df)} new files to be processed.”)
return merged_df[[‘filename’, ‘filepath’]]
except Exception as e:
logging.error(f”Error identifying new files: {e}”)
return pd.DataFrame(columns=[‘filename’, ‘filepath’])

def process_request(request):
logging.debug(“Processing request”)
try:
base_directory = os.getenv(“BASE_DIRECTORY”)
logging.debug(f”Base directory: {base_directory}”)

sftp_host = os.getenv(“SFTP_SERVER”)
sftp_user = os.getenv(“SFTP_USER”)
sftp_private_key_secret_name = os.getenv(“SFTP_KEY_SECRET”)
logging.debug(f”SFTP host: {sftp_host}, SFTP user: {sftp_user}, SFTP key secret name: {sftp_private_key_secret_name}”)

sftp_private_key = get_secret(sftp_private_key_secret_name)
if sftp_private_key is None:
logging.error(“Failed to retrieve the SFTP private key”)
return jsonify({‘error’: ‘Failed to retrieve the SFTP private key’}), 500

gcs_bucket = os.getenv(“GCS_BUCKET_NAME”)
logging.debug(f”GCS bucket: {gcs_bucket}”)

request_json = request.get_json(silent=True)
request_args = request.args

if request_json and ‘days_threshold’ in request_json:
days_threshold = request_json[‘days_threshold’]
elif request_args and ‘days_threshold’ in request_args:
days_threshold = request_args[‘days_threshold’]
else:
logging.warning(‘Days Parameter Error, Selecting Default (1)’)
days_threshold = 1

days_threshold = int(days_threshold)
logging.debug(f”Processing with days_threshold: {days_threshold}”)

sftp_client, ssh_client = create_sftp_connection(host=sftp_host, username=sftp_user, private_key_pem=sftp_private_key)

if sftp_client is None or ssh_client is None:
logging.error(“Failed to create SFTP connection”)
return jsonify({‘error’: ‘Failed to create SFTP connection’}), 500

new_files_df = identify_new_files(sftp_client, base_directory, days_threshold)

logging.info(f”{len(new_files_df)} new files are ready to download.”)

for filename, filepath in new_files_df[[‘filename’, ‘filepath’]].values:
fetch_file(sftp_client, base_directory + “/” + filepath, ‘/tmp/’ + filename)
transfer_to_gcs(gcs_bucket, ‘/tmp/’ + filename, filename) # Ensure the blob name is appropriate for your use case

sftp_client.close()
ssh_client.close()

return jsonify({‘message’: ‘Process completed successfully’, ‘files’: new_files_df.to_dict(orient=’records’)})

except Exception as e:
logging.error(f”Error in processing request: {e}”)
return jsonify({‘error’: str(e)}), 500