Add NoSuchProcess exception handling (#20059)

* Add NoSuchProcess exception handling

* Add changelog

* lint

* Add log validation in tests

Author: Kyle-Neale

gunicorn/changelog.d/20059.added

@@ -0,0 +1 @@
+Add NoSuchProcess exception handling during initial proc search

gunicorn/datadog_checks/gunicorn/gunicorn.py

@@ -151,6 +151,8 @@ def _get_master_proc_by_name(self, name):
             try:
                 if p.cmdline()[0] == master_name:
                     master_procs.append(p)
+            except psutil.NoSuchProcess:
+                self.log.debug("Process %s disappeared while scanning", p.name())
             except (IndexError, psutil.Error) as e:
                 self.log.debug("Cannot read information from process %s: %s", p.name(), e, exc_info=True)
         self.log.debug("There are %s master process(es) with the name %s", len(master_procs), name)

gunicorn/tests/test_unit.py

@@ -1,7 +1,10 @@
 # (C) Datadog, Inc. 2019-present
 # All rights reserved
 # Licensed under a 3-clause BSD style license (see LICENSE)
+import logging
+
 import mock
+import psutil
 import pytest
 
 from datadog_checks.gunicorn import GUnicornCheck
@@ -22,3 +25,29 @@ def test_collect_metadata_parsing_matching(aggregator, datadog_agent, stdout, st
         check.check(INSTANCE)
 
     datadog_agent.assert_metadata_count(expect_metadata_count)
+
+
+def test_process_disappearing_during_scan(aggregator, caplog):
+    """Test handling of processes that disappear during scanning"""
+    caplog.clear()
+    # Create a mock process that will raise NoSuchProcess when cmdline() is called
+    mock_process = mock.Mock()
+    mock_process.cmdline.side_effect = psutil.NoSuchProcess(1234)  # 1234 is the pid
+    mock_process.name.return_value = "dd-test-gunicorn"  # For the debug log message
+
+    check = GUnicornCheck(CHECK_NAME, {}, [INSTANCE])
+    caplog.set_level(logging.DEBUG)
+
+    # Mock process_iter to return our disappearing process
+    with mock.patch('psutil.process_iter', return_value=[mock_process]):
+        check.check(INSTANCE)
+
+    # Verify the service check shows critical since no processes were found
+    aggregator.assert_service_check(
+        "gunicorn.is_running",
+        check.CRITICAL,
+        tags=['app:' + INSTANCE['proc_name']],
+        message="No gunicorn process with name {} found, skipping worker metrics".format(INSTANCE['proc_name']),
+    )
+
+    assert "Process dd-test-gunicorn disappeared while scanning" in caplog.text