[DHCP] Add try/exception when using psutil.process_iter (sonic-net#19537

)

Why I did it
After got running process list by psutil, if some of the processes exited, but invoke name() / cmdline() function of them, it will raise NoSuchProcess exception
Fix issue sonic-net#19507

How I did it
Add try/exception in process execution
Change func get_target_process_cmds to get_target_process for reuse

How to verify it
UT passed

src/sonic-dhcp-utilities/dhcp_utilities/common/utils.py

@@ -160,8 +160,11 @@ def get_target_process_cmds(process_name):
     """
     res = []
     for proc in psutil.process_iter():
-        if proc.name() == process_name:
-            res.append(proc.cmdline())
+        try:
+            if proc.name() == process_name:
+                res.append(proc.cmdline())
+        except psutil.NoSuchProcess:
+            continue
     return res
 
 

src/sonic-dhcp-utilities/dhcp_utilities/dhcprelayd/dhcprelayd.py

@@ -319,16 +319,19 @@ def _kill_exist_relay_releated_process(self, new_dhcp_interfaces, process_name,
 
         # Get old dhcrelay process and get old dhcp interfaces
         for proc in psutil.process_iter():
-            if proc.name() == process_name:
-                cmds = proc.cmdline()
-                index = 0
-                target_procs.append(proc)
-                while index < len(cmds):
-                    if cmds[index] == "-id":
-                        old_dhcp_interfaces.add(cmds[index + 1])
-                        index += 2
-                    else:
-                        index += 1
+            try:
+                if proc.name() == process_name:
+                    cmds = proc.cmdline()
+                    index = 0
+                    target_procs.append(proc)
+                    while index < len(cmds):
+                        if cmds[index] == "-id":
+                            old_dhcp_interfaces.add(cmds[index + 1])
+                            index += 2
+                        else:
+                            index += 1
+            except psutil.NoSuchProcess:
+                continue
         if len(target_procs) == 0:
             return NOT_FOUND_PROC
 

src/sonic-dhcp-utilities/dhcp_utilities/dhcpservd/dhcpservd.py

@@ -39,9 +39,12 @@ def _notify_kea_dhcp4_proc(self):
         Send SIGHUP signal to kea-dhcp4 process
         """
         for proc in psutil.process_iter():
-            if KEA_DHCP4_PROC_NAME in proc.name():
-                proc.send_signal(signal.SIGHUP)
-                break
+            try:
+                if KEA_DHCP4_PROC_NAME in proc.name():
+                    proc.send_signal(signal.SIGHUP)
+                    break
+            except psutil.NoSuchProcess:
+                continue
 
     def dump_dhcp4_config(self):
         """

src/sonic-dhcp-utilities/tests/common_utils.py

@@ -65,17 +65,22 @@ def mock_get_config_db_table(table_name):
 
 
 class MockProc(object):
-    def __init__(self, name, pid=None, status=psutil.STATUS_RUNNING):
+    def __init__(self, name, pid=1, exited=False):
         self.proc_name = name
         self.pid = pid
+        self.exited = exited
 
     def name(self):
+        if self.exited:
+            raise psutil.NoSuchProcess(self.pid)
         return self.proc_name
 
     def send_signal(self, sig_num):
         pass
 
     def cmdline(self):
+        if self.exited:
+            raise psutil.NoSuchProcess(self.pid)
         if self.proc_name == "dhcrelay":
             return ["/usr/sbin/dhcrelay", "-d", "-m", "discard", "-a", "%h:%p", "%P", "--name-alias-map-file",
                     "/tmp/port-name-alias-map.txt", "-id", "Vlan1000", "-iu", "docker0", "240.127.1.2"]

src/sonic-dhcp-utilities/tests/test_dhcprelayd.py

@@ -111,6 +111,7 @@ def test_kill_exist_relay_releated_process(mock_swsscommon_dbconnector_init, new
     process_iter_ret = []
     for running_proc in running_procs:
         process_iter_ret.append(MockProc(running_proc))
+    process_iter_ret.append(MockProc("exited_proc", exited=True))
     with patch.object(psutil, "process_iter", return_value=process_iter_ret), \
          patch.object(ConfigDbEventChecker, "enable"):
         dhcp_db_connector = DhcpDbConnector()
@@ -194,23 +195,23 @@ def test_execute_supervisor_dhcp_relay_process(mock_swsscommon_dbconnector_init,
             mock_run.assert_called_once_with(["supervisorctl", op, "dhcpmon-Vlan1000"], check=True)
 
 
-@pytest.mark.parametrize("target_cmds", [[["/usr/bin/dhcrelay"]], [["/usr/bin/dhcpmon"]]])
-def test_check_dhcp_relay_process(mock_swsscommon_dbconnector_init, mock_swsscommon_table_init, target_cmds):
-    exp_config = {"isc-dhcpv4-relay-Vlan1000": ["/usr/bin/dhcrelay"]}
-    with patch("dhcp_utilities.dhcprelayd.dhcprelayd.get_target_process_cmds", return_value=target_cmds), \
+@pytest.mark.parametrize("target_procs_cmds", [[["dhcrelay", "-d"]], [["dhcpmon"]]])
+def test_check_dhcp_relay_process(mock_swsscommon_dbconnector_init, mock_swsscommon_table_init, target_procs_cmds):
+    exp_config = {
+        "isc-dhcpv4-relay-Vlan1000": ["dhcrelay", "-d"]
+    }
+    with patch("dhcp_utilities.dhcprelayd.dhcprelayd.get_target_process_cmds", return_value=target_procs_cmds), \
          patch.object(DhcpRelayd, "dhcp_relay_supervisor_config",
                       return_value=exp_config, new_callable=PropertyMock), \
          patch.object(sys, "exit", mock_exit_func):
         dhcp_db_connector = DhcpDbConnector()
         dhcprelayd = DhcpRelayd(dhcp_db_connector, None)
-        exp_cmds = [value for key, value in exp_config.items() if "isc-dhcpv4-relay" in key]
-        exp_cmds.sort()
         try:
             dhcprelayd._check_dhcp_relay_processes()
         except SystemExit:
-            assert exp_cmds != target_cmds
+            assert target_procs_cmds[0] != exp_config["isc-dhcpv4-relay-Vlan1000"]
         else:
-            assert exp_cmds == target_cmds
+            assert target_procs_cmds[0] == exp_config["isc-dhcpv4-relay-Vlan1000"]
 
 
 def test_get_dhcp_relay_config(mock_swsscommon_dbconnector_init, mock_swsscommon_table_init):

src/sonic-dhcp-utilities/tests/test_dhcpservd.py

@@ -66,6 +66,7 @@ def test_dump_dhcp4_config(mock_swsscommon_dbconnector_init, enabled_checker):
 def test_notify_kea_dhcp4_proc(process_list, mock_swsscommon_dbconnector_init, mock_get_render_template,
                                mock_parse_port_map_alias):
     proc_list = [MockProc(process_name) for process_name in process_list]
+    proc_list.append(MockProc("exited_proc", exited=True))
     with patch.object(psutil, "process_iter", return_value=proc_list), \
          patch.object(MockProc, "send_signal", MagicMock()) as mock_send_signal:
         dhcp_db_connector = DhcpDbConnector()

src/sonic-dhcp-utilities/tests/test_utils.py

@@ -142,7 +142,9 @@ def test_validate_ttr_type(test_data):
 
 
 def test_get_target_process_cmds():
-    with patch.object(psutil, "process_iter", return_value=[MockProc("dhcrelay", 1), MockProc("dhcpmon", 2)],
+    with patch.object(psutil, "process_iter", return_value=[MockProc("dhcrelay", 1),
+                                                            MockProc("dhcrelay", 1, exited=True),
+                                                            MockProc("dhcpmon", 2)],
                       new_callable=PropertyMock):
         res = utils.get_target_process_cmds("dhcrelay")
         expected_res = [