sftp_to_wasb.py

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"""This module contains SFTP to Azure Blob Storage operator."""
import os
import sys
from collections import namedtuple
from tempfile import NamedTemporaryFile
from typing import Dict, List, Optional, Tuple

if sys.version_info >= (3, 8):
    from functools import cached_property
else:
    from cached_property import cached_property

from airflow.exceptions import AirflowException
from airflow.models import BaseOperator
from airflow.providers.microsoft.azure.hooks.wasb import WasbHook
from airflow.providers.sftp.hooks.sftp import SFTPHook

WILDCARD = "*"
SftpFile = namedtuple('SftpFile', 'sftp_file_path, blob_name')


class SFTPToWasbOperator(BaseOperator):
    """
    Transfer files to Azure Blob Storage from SFTP server.

    .. seealso::
        For more information on how to use this operator, take a look at the guide:
        :ref:`howto/operator:SFTPToWasbOperator`

    :param sftp_source_path: The sftp remote path. This is the specified file path
        for downloading the single file or multiple files from the SFTP server.
        You can use only one wildcard within your path. The wildcard can appear
        inside the path or at the end of the path.
    :type sftp_source_path: str
    :param container_name: Name of the container.
    :type container_name: str
    :param blob_prefix: Prefix to name a blob.
    :type blob_prefix: str
    :param sftp_conn_id: The sftp connection id. The name or identifier for
        establishing a connection to the SFTP server.
    :type sftp_conn_id: str
    :param wasb_conn_id: Reference to the wasb connection.
    :type wasb_conn_id: str
    :param load_options: Optional keyword arguments that
        ``WasbHook.load_file()`` takes.
    :type load_options: dict
    :param move_object: When move object is True, the object is moved instead
        of copied to the new location. This is the equivalent of a mv command
        as opposed to a cp command.
    :param wasb_overwrite_object: Whether the blob to be uploaded
        should overwrite the current data.
        When wasb_overwrite_object is True, it will overwrite the existing data.
        If set to False, the operation might fail with
        ResourceExistsError in case a blob object already exists.
    :type move_object: bool
    """

    template_fields = ("sftp_source_path", "container_name", "blob_prefix")

    def __init__(
        self,
        *,
        sftp_source_path: str,
        container_name: str,
        blob_prefix: str = "",
        sftp_conn_id: str = "sftp_default",
        wasb_conn_id: str = 'wasb_default',
        load_options: Optional[Dict] = None,
        move_object: bool = False,
        wasb_overwrite_object: bool = False,
        **kwargs,
    ) -> None:
        super().__init__(**kwargs)

        self.sftp_source_path = sftp_source_path
        self.blob_prefix = blob_prefix
        self.sftp_conn_id = sftp_conn_id
        self.wasb_conn_id = wasb_conn_id
        self.container_name = container_name
        self.wasb_conn_id = wasb_conn_id
        self.load_options = load_options or {"overwrite": wasb_overwrite_object}
        self.move_object = move_object

    def dry_run(self) -> None:
        super().dry_run()
        sftp_files: List[SftpFile] = self.get_sftp_files_map()
        for file in sftp_files:
            self.log.info(
                'Process will upload file from (SFTP) %s to wasb://%s as %s',
                file.sftp_file_path,
                self.container_name,
                file.blob_name,
            )
            if self.move_object:
                self.log.info("Executing delete of %s", file)

    def execute(self, context: Dict) -> None:
        """Upload a file from SFTP to Azure Blob Storage."""
        sftp_files: List[SftpFile] = self.get_sftp_files_map()
        uploaded_files = self.copy_files_to_wasb(sftp_files)
        if self.move_object:
            self.delete_files(uploaded_files)

    def get_sftp_files_map(self) -> List[SftpFile]:
        """Get SFTP files from the source path, it may use a WILDCARD to this end."""
        sftp_files = []

        sftp_complete_path, prefix, delimiter = self.get_tree_behavior()

        found_files, _, _ = self.sftp_hook.get_tree_map(
            sftp_complete_path, prefix=prefix, delimiter=delimiter
        )

        self.log.info("Found %s files at sftp source path: %s", str(len(found_files)), self.sftp_source_path)

        for file in found_files:
            future_blob_name = self.get_full_path_blob(file)
            sftp_files.append(SftpFile(file, future_blob_name))

        return sftp_files

    def get_tree_behavior(self) -> Tuple[str, Optional[str], Optional[str]]:
        """Extracts from source path the tree behavior to interact with the remote folder"""
        self.check_wildcards_limit()

        if self.source_path_contains_wildcard:

            prefix, delimiter = self.sftp_source_path.split(WILDCARD, 1)

            sftp_complete_path = os.path.dirname(prefix)

            return sftp_complete_path, prefix, delimiter

        return self.sftp_source_path, None, None

    def check_wildcards_limit(self) -> None:
        """Check if there are multiple wildcards used in the SFTP source path."""
        total_wildcards = self.sftp_source_path.count(WILDCARD)
        if total_wildcards > 1:
            raise AirflowException(
                "Only one wildcard '*' is allowed in sftp_source_path parameter. "
                f"Found {total_wildcards} in {self.sftp_source_path}."
            )

    @property
    def source_path_contains_wildcard(self) -> bool:
        """Checks if the SFTP source path contains a wildcard."""
        return WILDCARD in self.sftp_source_path

    @cached_property
    def sftp_hook(self) -> SFTPHook:
        """Property of sftp hook to be re-used."""
        return SFTPHook(self.sftp_conn_id)

    def get_full_path_blob(self, file: str) -> str:
        """Get a blob name based on the previous name and a blob_prefix variable"""
        return self.blob_prefix + os.path.basename(file)

    def copy_files_to_wasb(self, sftp_files: List[SftpFile]) -> List[str]:
        """Upload a list of files from sftp_files to Azure Blob Storage with a new Blob Name."""
        uploaded_files = []
        wasb_hook = WasbHook(wasb_conn_id=self.wasb_conn_id)
        for file in sftp_files:
            with NamedTemporaryFile("w") as tmp:
                self.sftp_hook.retrieve_file(file.sftp_file_path, tmp.name)
                self.log.info(
                    'Uploading %s to wasb://%s as %s',
                    file.sftp_file_path,
                    self.container_name,
                    file.blob_name,
                )
                wasb_hook.load_file(tmp.name, self.container_name, file.blob_name, **self.load_options)

                uploaded_files.append(file.sftp_file_path)

        return uploaded_files

    def delete_files(self, uploaded_files: List[str]) -> None:
        """Delete files at SFTP which have been moved to Azure Blob Storage."""
        for sftp_file_path in uploaded_files:
            self.log.info("Executing delete of %s", sftp_file_path)
            self.sftp_hook.delete_file(sftp_file_path)