[GitHub] [airflow] turbaszek commented on a change in pull request #12814: Add Apache Beam operators

[GitBox <gi...@apache.org>]

turbaszek commented on a change in pull request #12814:
URL: https://github.com/apache/airflow/pull/12814#discussion_r536431621



##########
File path: airflow/providers/apache/beam/hooks/beam.py
##########
@@ -0,0 +1,234 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""This module contains a Apache Beam Hook."""
+import json
+import select
+import shlex
+import subprocess
+import textwrap
+from tempfile import TemporaryDirectory
+from typing import List, Optional
+
+from airflow.exceptions import AirflowException
+from airflow.hooks.base_hook import BaseHook
+from airflow.utils.log.logging_mixin import LoggingMixin
+from airflow.utils.python_virtualenv import prepare_virtualenv
+
+
+class _BeamRunner(LoggingMixin):
+    def __init__(
+        self,
+        cmd: List[str],
+    ) -> None:
+        super().__init__()
+        self.log.info("Running command: %s", " ".join(shlex.quote(c) for c in cmd))
+        self._proc = subprocess.Popen(
+            cmd,
+            shell=False,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+            close_fds=True,
+        )
+
+    def _process_fd(self, fd):
+        """
+        Prints output to logs.
+
+        :param fd: File descriptor.
+        """
+        if fd == self._proc.stderr:
+            while True:
+                line = self._proc.stderr.readline().decode()
+                if not line:
+                    return
+                self.log.warning(line.rstrip("\n"))
+
+        if fd == self._proc.stdout:
+            while True:
+                line = self._proc.stdout.readline().decode()
+                if not line:
+                    return
+                self.log.info(line.rstrip("\n"))
+
+        raise Exception("No data in stderr or in stdout.")
+
+    def wait_for_done(self) -> None:
+        """Waits for Apache Beam pipeline to complete."""
+        self.log.info("Start waiting for Apache Beam process to complete.")
+        reads = [self._proc.stderr, self._proc.stdout]
+        while True:
+            # Wait for at least one available fd.
+            readable_fds, _, _ = select.select(reads, [], [], 5)
+            if readable_fds is None:
+                self.log.info("Waiting for Apache Beam process to complete.")
+                continue
+
+            for readable_fd in readable_fds:
+                self._process_fd(readable_fd)
+
+            if self._proc.poll() is not None:
+                break
+
+        # Corner case: check if more output was created between the last read and the process termination
+        for readable_fd in reads:
+            self._process_fd(readable_fd)
+
+        self.log.info("Process exited with return code: %s", self._proc.returncode)
+
+        if self._proc.returncode != 0:
+            raise Exception(f"Apache Beam process failed with return code {self._proc.returncode}")
+
+
+class BeamHook(BaseHook):
+    """
+    Hook for Apache Beam.
+
+    All the methods in the hook where project_id is used must be called with
+    keyword arguments rather than positional.
+    """
+
+    def __init__(
+        self,
+        runner: str,
+    ) -> None:
+        self.runner = runner
+        super().__init__()
+
+    def _start_pipeline(
+        self,
+        variables: dict,
+        command_prefix: List[str],
+    ) -> None:
+        cmd = command_prefix + [
+            f"--runner={self.runner}",
+        ]
+        if variables:
+            cmd.extend(self._options_to_args(variables))
+        _BeamRunner(cmd=cmd).wait_for_done()

Review comment:
       Should we allow async mode (op + sensor)? So the running pipeline is not blocking worker slot? I suppose this may be hard as we are running a subprocess




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