Implement "get_process_count_by_name" natively

Use Python native libraries instead of shell calls.

Closes-Bug: #1900269

Change-Id: If6eafb7f5f26ab127ab5432ce85096d052a20b0c

lower-constraints.txt

@@ -89,7 +89,7 @@ pika-pool==0.1.3
 pika==0.10.0
 positional==1.2.1
 prettytable==0.7.2
-psutil==3.2.2
+psutil==5.3.0
 pycadf==1.1.0
 pycparser==2.18
 Pygments==2.2.0

neutron/agent/linux/utils.py

@@ -195,13 +195,8 @@ def find_parent_pid(pid):
 
 def get_process_count_by_name(name):
     """Find the process count by name."""
-    try:
-        out = execute(['ps', '-C', name, '-o', 'comm='],
-                      log_fail_as_error=False)
-    except exceptions.ProcessExecutionError:
-        with excutils.save_and_reraise_exception(reraise=False):
-            return 0
-    return len(out.strip('\n').split('\n'))
+    return len([p for p in psutil.process_iter(['name']) if
+                p.info['name'] == name])
 
 
 def find_fork_top_parent(pid):

neutron/tests/functional/agent/linux/test_utils.py

@@ -118,3 +118,26 @@ class TestFindParentPid(functional_base.BaseSudoTestCase):
 
     def test_non_root_process(self):
         self._test_process(run_as_root=False)
+
+
+class TestGetProcessCountByName(functional_base.BaseSudoTestCase):
+
+    def _stop_processes(self, processes):
+        for process in processes:
+            process.stop(kill_signal=signal.SIGKILL)
+
+    def test_root_process(self):
+        cmd = ['sleep', '100']
+        processes = []
+        for _ in range(20):
+            process = async_process.AsyncProcess(cmd)
+            process.start()
+            processes.append(process)
+        for process in processes:
+            common_utils.wait_until_true(lambda: process._process.pid,
+                                         sleep=0.5, timeout=5)
+        self.addCleanup(self._stop_processes, processes)
+        number_of_sleep = utils.get_process_count_by_name('sleep')
+        # NOTE(ralonsoh): other tests can spawn sleep processes too, but at
+        # this point we know there are, at least, 20 "sleep" processes running.
+        self.assertLessEqual(20, number_of_sleep)

requirements.txt

@@ -46,7 +46,7 @@ osprofiler>=2.3.0 # Apache-2.0
 os-ken >= 0.3.0 # Apache-2.0
 ovs>=2.8.0 # Apache-2.0
 ovsdbapp>=1.4.0 # Apache-2.0
-psutil>=3.2.2 # BSD
+psutil>=5.3.0 # BSD
 pyroute2>=0.5.13;sys_platform!='win32' # Apache-2.0 (+ dual licensed GPL2)
 pyOpenSSL>=17.1.0 # Apache-2.0