From 0e8b1c8f59bd1b57d31b7d31ba82c4efa6149d0a Mon Sep 17 00:00:00 2001
From: Sofia Kopikova <s.kopikova@postgrespro.ru>
Date: Thu, 23 Mar 2023 13:33:46 +0300
Subject: [PATCH] Catch FileNotFoundError exception

When we want to find some Postgres process in testgres psutils lib first gets list of all system processes (children() function in testgres's auxiliary_processes). Next testgres asks for process name (cmdline() function), so psutils goes to /proc/pid/ in Linux. In case any of processes listed in previous step, we get FileNotFoundError
---
 testgres/enums.py    | 13 +++++++++----
 tests/test_simple.py | 14 ++++++++++++++
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/testgres/enums.py b/testgres/enums.py
index fb68f2bb..d07d8068 100644
--- a/testgres/enums.py
+++ b/testgres/enums.py
@@ -1,5 +1,6 @@
 from enum import Enum, IntEnum
 from six import iteritems
+from psutil import NoSuchProcess
 
 
 class XLogMethod(Enum):
@@ -68,11 +69,15 @@ def from_process(process):
             ],
         }  # yapf: disable
 
+        try:
+            cmdline = ''.join(process.cmdline())
+        except (FileNotFoundError, ProcessLookupError, NoSuchProcess):
+            return ProcessType.Unknown
+
         # we deliberately cut special words and spaces
-        cmdline = ''.join(process.cmdline()) \
-                    .replace('postgres:', '', 1) \
-                    .replace('bgworker:', '', 1) \
-                    .replace(' ', '')
+        cmdline = cmdline.replace('postgres:', '', 1) \
+            .replace('bgworker:', '', 1) \
+            .replace(' ', '')
 
         for ptype in ProcessType:
             if cmdline.startswith(ptype.value.replace(' ', '')):
diff --git a/tests/test_simple.py b/tests/test_simple.py
index 9ddf5baa..d79fa79a 100755
--- a/tests/test_simple.py
+++ b/tests/test_simple.py
@@ -9,6 +9,7 @@
 import time
 import six
 import unittest
+import psutil
 
 import logging.config
 
@@ -48,6 +49,7 @@
 # NOTE: those are ugly imports
 from testgres import bound_ports
 from testgres.utils import PgVer
+from testgres.node import ProcessProxy
 
 
 def pg_version_ge(version):
@@ -965,6 +967,18 @@ def test_child_pids(self):
                 with self.assertRaises(TestgresException):
                     replica.source_walsender
 
+    def test_child_process_dies(self):
+        # test for FileNotFound exception during child_processes() function
+        with subprocess.Popen(["sleep", "60"]) as process:
+            self.assertEqual(process.poll(), None)
+            # collect list of processes currently running
+            children = psutil.Process(os.getpid()).children()
+            # kill a process, so received children dictionary becomes invalid
+            process.kill()
+            process.wait()
+            # try to handle children list -- missing processes will have ptype "ProcessType.Unknown"
+            [ProcessProxy(p) for p in children]
+
 
 if __name__ == '__main__':
     if os.environ.get('ALT_CONFIG'):