[GitHub] [airflow] bolkedebruin commented on a change in pull request #6627: [AIRFLOW-5931] Use os.fork when appropriate to speed up task execution.

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

bolkedebruin commented on a change in pull request #6627: [AIRFLOW-5931] Use os.fork when appropriate to speed up task execution.
URL: https://github.com/apache/airflow/pull/6627#discussion_r349343728
 
 

 ##########
 File path: airflow/task/task_runner/standard_task_runner.py
 ##########
 @@ -17,28 +17,89 @@
 # specific language governing permissions and limitations
 # under the License.
 
+import os
+
 import psutil
+from setproctitle import setproctitle
 
 from airflow.task.task_runner.base_task_runner import BaseTaskRunner
 from airflow.utils.helpers import reap_process_group
 
+CAN_FORK = hasattr(os, 'fork')
+
 
 class StandardTaskRunner(BaseTaskRunner):
     """
     Runs the raw Airflow task by invoking through the Bash shell.
     """
     def __init__(self, local_task_job):
         super().__init__(local_task_job)
+        self._rc = None
 
     def start(self):
-        self.process = self.run_command()
+        if CAN_FORK and not self.run_as_user:
+            self.process = self._start_by_fork()
+        else:
+            self.process = self._start_by_exec()
+
+    def _start_by_exec(self):
+        subprocess = self.run_command()
+        return psutil.Process(subprocess.pid)
+
+    def _start_by_fork(self):
+        pid = os.fork()
+        if pid:
+            self.log.info("Started process %d to run task", pid)
+            return psutil.Process(pid)
+        else:
+            from airflow.bin.cli import get_parser
+            import signal
+            import airflow.settings as settings
+
+            signal.signal(signal.SIGINT, signal.SIG_DFL)
+            signal.signal(signal.SIGTERM, signal.SIG_DFL)
+            # Start a new process group
+            os.setpgid(0, 0)
+
+            # Force a new SQLAlchemy session. We can't share open DB handles between process.
+            settings.engine.pool.dispose()
+            settings.engine.pool.recreate()
+
+            parser = get_parser()
+            args = parser.parse_args(self._command[1:])
+            setproctitle(
+                "airflow task runner: {0.dag_id} {0.task_id} {0.execution_date} {0.job_id}".format(args)
+            )
+            try:
+                args.func(args)
+                os._exit(0)
+            except Exception:
+                os._exit(1)
+
+    def return_code(self, timeout=0):
+        # We call this multiple times, but we can only wait on the process once
+        if self._rc is not None or not self.process:
+            return self._rc
+
+        try:
+            self._rc = self.process.wait(timeout=timeout)
+            self.process = None
+        except psutil.TimeoutExpired:
+            pass
 
-    def return_code(self):
-        return self.process.poll()
+        return self._rc
 
     def terminate(self):
-        if self.process and psutil.pid_exists(self.process.pid):
-            reap_process_group(self.process.pid, self.log)
+        if self.process:
+            if self.process.is_running():
+                reap_process_group(self.process.pid, self.log)
 
 Review comment:
   NIT: process groups are undeterministic. We would be better off using cgroups

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