webhdfs.py

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"""Hook for Web HDFS."""
from __future__ import annotations

import logging
import socket
from typing import Any

import requests
from hdfs import HdfsError, InsecureClient

from airflow.configuration import conf
from airflow.exceptions import AirflowException
from airflow.hooks.base import BaseHook

log = logging.getLogger(__name__)

_kerberos_security_mode = conf.get("core", "security") == "kerberos"
if _kerberos_security_mode:
    try:
        from hdfs.ext.kerberos import KerberosClient
    except ImportError:
        log.error("Could not load the Kerberos extension for the WebHDFSHook.")
        raise


class AirflowWebHDFSHookException(AirflowException):
    """Exception specific for WebHDFS hook."""


class WebHDFSHook(BaseHook):
    """
    Interact with HDFS. This class is a wrapper around the hdfscli library.

    :param webhdfs_conn_id: The connection id for the webhdfs client to connect to.
    :param proxy_user: The user used to authenticate.
    """

    def __init__(self, webhdfs_conn_id: str = "webhdfs_default", proxy_user: str | None = None):
        super().__init__()
        self.webhdfs_conn_id = webhdfs_conn_id
        self.proxy_user = proxy_user

    def get_conn(self) -> Any:
        """
        Establishes a connection depending on the security mode set via config or environment variable.

        :return: a hdfscli InsecureClient or KerberosClient object.
        """
        connection = self._find_valid_server()
        if connection is None:
            raise AirflowWebHDFSHookException("Failed to locate the valid server.")
        return connection

    def _find_valid_server(self) -> Any:
        connection = self.get_connection(self.webhdfs_conn_id)
        namenodes = connection.host.split(",")
        for namenode in namenodes:
            host_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            self.log.info("Trying to connect to %s:%s", namenode, connection.port)
            try:
                conn_check = host_socket.connect_ex((namenode, connection.port))
                if conn_check == 0:
                    self.log.info("Trying namenode %s", namenode)
                    client = self._get_client(
                        namenode,
                        connection.port,
                        connection.login,
                        connection.get_password(),
                        connection.schema,
                        connection.extra_dejson,
                    )
                    client.status("/")
                    self.log.info("Using namenode %s for hook", namenode)
                    host_socket.close()
                    return client
                else:
                    self.log.warning("Could not connect to %s:%s", namenode, connection.port)
            except HdfsError as hdfs_error:
                self.log.info("Read operation on namenode %s failed with error: %s", namenode, hdfs_error)
        return None

    def _get_client(
        self, namenode: str, port: int, login: str, password: str | None, schema: str, extra_dejson: dict
    ) -> Any:
        connection_str = f"http://{namenode}"
        session = requests.Session()
        if password is not None:
            session.auth = (login, password)

        if extra_dejson.get("use_ssl", "False") == "True" or extra_dejson.get("use_ssl", False):
            connection_str = f"https://{namenode}"
            session.verify = extra_dejson.get("verify", False)

        if port is not None:
            connection_str += f":{port}"

        if schema is not None:
            connection_str += f"/{schema}"

        if _kerberos_security_mode:
            return KerberosClient(connection_str, session=session)
        proxy_user = self.proxy_user or login
        return InsecureClient(connection_str, user=proxy_user, session=session)

    def check_for_path(self, hdfs_path: str) -> bool:
        """
        Check for the existence of a path in HDFS by querying FileStatus.

        :param hdfs_path: The path to check.
        :return: True if the path exists and False if not.
        """
        conn = self.get_conn()

        status = conn.status(hdfs_path, strict=False)
        return bool(status)

    def load_file(
        self, source: str, destination: str, overwrite: bool = True, parallelism: int = 1, **kwargs: Any
    ) -> None:
        r"""
        Uploads a file to HDFS.

        :param source: Local path to file or folder.
            If it's a folder, all the files inside of it will be uploaded.
            .. note:: This implies that folders empty of files will not be created remotely.

        :param destination: PTarget HDFS path.
            If it already exists and is a directory, files will be uploaded inside.
        :param overwrite: Overwrite any existing file or directory.
        :param parallelism: Number of threads to use for parallelization.
            A value of `0` (or negative) uses as many threads as there are files.
        :param kwargs: Keyword arguments forwarded to :meth:`hdfs.client.Client.upload`.
        """
        conn = self.get_conn()

        conn.upload(
            hdfs_path=destination, local_path=source, overwrite=overwrite, n_threads=parallelism, **kwargs
        )
        self.log.debug("Uploaded file %s to %s", source, destination)

    def read_file(self, filename: str) -> bytes:
        """Read a file from HDFS.

        :param filename: The path of the file to read.
        :return: File content as a raw string
        """
        conn = self.get_conn()

        with conn.read(filename) as reader:
            content = reader.read()
        return content