Open a remote file using paramiko in python slow

Question

I am using paramiko to open a remote sftp file in python. With the file object returned by paramiko, I am reading the file line by line and processing the information. This seems really slow compared to using the python in-built method 'open' from the os. Following is the code I am using to get the file object.

Using paramiko (slower by 2 times) -

client = paramiko.SSHClient()
client.load_system_host_keys()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect(myHost,myPort,myUser,myPassword)
sftp = client.open_sftp()
fileObject = sftp.file(fullFilePath,'rb')

Using os -

import os
fileObject = open(fullFilePath,'rb')

Am I missing anything? Is there a way to make the paramiko fileobject read method as fast as the one using the os fileobject?

Thanks!!

Answer 1

Your problem is likely to be caused by the file being a remote object. You've opened it on the server and are requesting one line at a time - because it's not local, each request takes much longer than if the file was sitting on your hard drive. The best alternative is probably to copy the file down to a local location first, using Paramiko's SFTP get.

Once you've done that, you can open the file from the local location using os.open.

Answer 2

I was having the same issue and I could not afford to copy the file locally because of security reasons, I solved it by using a combination of prefetching and bytesIO:

def fetch_file_as_bytesIO(sftp, path):
    """
    Using the sftp client it retrieves the file on the given path by using pre fetching.
    :param sftp: the sftp client
    :param path: path of the file to retrieve
    :return: bytesIO with the file content
    """
    with sftp.file(path, mode='rb') as file:
        file_size = file.stat().st_size
        file.prefetch(file_size)
        file.set_pipelined()
        return io.BytesIO(file.read(file_size))