ccmlib/common.py: update pid_listening_on to return multiple pids

in some situations, like when running cassandra 4.1, we can endup
with some of the commands in this function return multiple pids
and not just one process

to handle that we just return all of the pids back.
in the enad it's just used for debug printing about who's holding
the ports.

ccmlib/common.py

@@ -730,15 +730,15 @@ def validate_install_dir(install_dir):
             raise ArgumentError(f'{install_dir} does not appear to be a cassandra or dse installation directory')
 
 
-def pid_listening_on(addr: str, port: int):
+def pids_listening_on(addr: str, port: int) -> List[int]:
     '''get pid of the process listening on the given port'''
-    pid = -1
+    pids = []
     if lsof := shutil.which('lsof'):
         result = subprocess.run([lsof, '-t', '-i', f'tcp@{addr}:{port}'],
                                 stdout=subprocess.PIPE,
                                 check=True)
         if result.stdout:
-            pid = int(result.stdout)
+            pids = [int(p) for p in result.stdout.split()]
     elif ss := shutil.which('ss'):
         result = subprocess.run([ss,
                                  '--no-header',
@@ -748,12 +748,12 @@ def pid_listening_on(addr: str, port: int):
                                  f'src = inet:{addr}:{port}'],
                                 stdout=subprocess.PIPE,
                                 check=True)
-        matched = re.search(r'pid=(\d+)', result.stdout)
+        matched = re.search(r'pid=(\d+)', str(result.stdout))
         if matched is not None:
-            pid = int(matched.group(1))
+            pids = [int(matched.group(1))]
     else:
         logger.info("neither lsof nor ss was found")
-    return pid
+    return pids
 
 
 def check_socket_available(itf):
@@ -771,18 +771,19 @@ def check_socket_available(itf):
     except socket.error as msg:
         s.close()
         addr, port = itf
-        pid = pid_listening_on(addr, port)
-        if pid == -1:
+        pids = pids_listening_on(addr, port)
+        if not pids:
             logger.error('Address %s:%d used unknown process')
         else:
-            p = psutil.Process(pid)
-            secs_ago = p.create_time()
-            fmt = '%H:%M:%S' if secs_ago < 60 * 60 * 24 else '%Y-%m-%d %H:%M:%S'
-            since = datetime.fromtimestamp(secs_ago).strftime(fmt)
-            logger.error('Address %s:%d used by: "%s" '
-                         '(pid: %d, since: %s, parent: "%s")',
-                         addr, port, ' '.join(p.cmdline()),
-                         p.pid, since, ' '.join(p.parent().cmdline()))
+            for pid in pids:
+                p = psutil.Process(pid)
+                secs_ago = p.create_time()
+                fmt = '%H:%M:%S' if secs_ago < 60 * 60 * 24 else '%Y-%m-%d %H:%M:%S'
+                since = datetime.fromtimestamp(secs_ago).strftime(fmt)
+                logger.error('Address %s:%d used by: "%s" '
+                             '(pid: %d, since: %s, parent: "%s")',
+                             addr, port, ' '.join(p.cmdline()),
+                             p.pid, since, ' '.join(p.parent().cmdline()))
         raise UnavailableSocketError(f'Inet address {addr}:{port} is not available: {msg}')