compatibility to python3 and usage of CLI maxctrl

check_maxscale

@@ -1,19 +1,18 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 #
 # Author:  Fabien Hochstrasser <fabien.hochstrasser@swisscom.com>
 # Date:    2018-04-03
 # Purpose: Nagios check to monitor the MaxScale SQL proxy.
 #
-# This script uses the maxadmin CLI to read the status of MaxScale.
+# This script uses the maxctrl CLI to read the status of MaxScale.
 #
 # Usage: see --help
 #
 import argparse
 import os
 import subprocess
 import sys
-
 from collections import namedtuple
 
 Server = namedtuple('Server', 'name address port connections status')
@@ -34,19 +33,19 @@ def main(args):
     problems = []
 
     try:
-        servers = maxadmin_list_servers()
-        sessions = maxadmin_list_sessions()
-        monitors = maxadmin_list_monitors()
+        servers = maxctrl_list_servers()
+        sessions = maxctrl_list_sessions()
+        monitors = maxctrl_list_monitors()
     except subprocess.CalledProcessError:
         problems.append(Problem(
-            message='MaxScale doesn\'t seem to be running',
+            message="MaxScale doesn't seem to be running",
             severity=CRITICAL,
         ))
 
     problems.extend(
-        check_servers(servers, args.expected_number_of_servers, args.connections_threshold) + \
-        check_sessions(sessions, args.sessions_threshold) + \
-        check_monitors(monitors)
+        check_servers(servers, args.expected_number_of_servers, args.connections_threshold)
+        + check_sessions(sessions, args.sessions_threshold)
+        + check_monitors(monitors)
     )
 
     if args.verbose:
@@ -64,31 +63,33 @@ def main(args):
         print('')
         print('Problems')
         for problem in problems:
-            print problem
+            print(problem)
 
     print_message(problems)
     sys.exit(
-        CRITICAL if any([p.severity == CRITICAL for p in problems])
-        else WARNING if any([p.severity == WARNING for p in problems])
+        CRITICAL if any(p.severity == CRITICAL for p in problems)
+        else WARNING if any(p.severity == WARNING for p in problems)
         else OK
     )
 
 
-def maxadmin_list_servers():
-    """Return the servers known to MaxScale.
-
-    The command 'maxadmin list servers' is used.
-    """
-    servers = []
-
+def _run_maxctrl_list(what):
     devnull = open(os.devnull, 'w')
-    for line in subprocess.check_output(
-        ['maxadmin', 'list', 'servers'],
+    out = subprocess.check_output(
+        ['maxctrl', '--tsv', 'list', what],
         stderr=devnull,
-        close_fds=True,
-    ).split('\n'):
+    )
+    if isinstance(out, bytes):
+        out = out.decode('utf-8', errors='replace')
+    return out.split('\n')
+
+
+def maxctrl_list_servers():
+    """Return the servers known to MaxScale."""
+    servers = []
+    for line in _run_maxctrl_list('servers'):
         try:
-            fields = [field.strip() for field in line.split('|')]
+            fields = [field.strip() for field in line.split('\t')]
             servers.append(Server(
                 name=fields[0],
                 address=fields[1],
@@ -97,105 +98,77 @@ def maxadmin_list_servers():
                 status={s.strip() for s in fields[4].split(',')},
             ))
         except (ValueError, IndexError):
-            # If the line cannot be parsed, just ignore it. It's a header line.
             pass
-
     return servers
 
 
-def maxadmin_list_sessions():
-    """Return the sessions established to MaxScale.
-
-    The command 'maxadmin list sessions' is used.
-    """
+def maxctrl_list_sessions():
+    """Return the sessions established to MaxScale."""
     sessions = []
-
-    devnull = open(os.devnull, 'w')
-    for line in subprocess.check_output(
-        ['maxadmin', 'list', 'sessions'],
-        stderr=devnull,
-        close_fds=True,
-    ).split('\n'):
+    for line in _run_maxctrl_list('sessions'):
         try:
-            fields = [field.strip() for field in line.split('|')]
+            fields = [field.strip() for field in line.split('\t')]
             sessions.append(Session(
                 id=int(fields[0]),
                 client=fields[1],
                 service=fields[2],
                 state=fields[3],
             ))
         except (ValueError, IndexError):
-            # If the line cannot be parsed, just ignore it. It's a header line.
             pass
-
     return sessions
 
 
-def maxadmin_list_monitors():
-    """Return the monitors configured in MaxScale.
-
-    The command 'maxadmin list monitors' is used.
-    """
+def maxctrl_list_monitors():
+    """Return the monitors configured in MaxScale."""
     monitors = []
-
-    devnull = open(os.devnull, 'w')
-    for line in subprocess.check_output(
-        ['maxadmin', 'list', 'monitors'],
-        stderr=devnull,
-        close_fds=True,
-    ).split('\n'):
+    for line in _run_maxctrl_list('monitors'):
         try:
-            fields = [field.strip() for field in line.split('|')]
-            # Ignore the header line
+            fields = [field.strip() for field in line.split('\t')]
             if fields[1] != 'Status':
                 monitors.append(Monitor(
                     name=fields[0],
                     status=fields[1],
                 ))
         except (ValueError, IndexError):
-            # If the line cannot be parsed, just ignore it. It's a header line.
             pass
-
     return monitors
 
 
 def check_servers(servers, expected_number_of_servers, connections_threshold):
     problems = []
     problems.append(check_servers_count(len(servers), expected_number_of_servers))
     problems.append(check_servers_no_master(servers))
-
     for server in servers:
         problems.append(check_server_status(server))
         problems.append(check_server_connections(server, connections_threshold))
-
     return [p for p in problems if p is not None]
 
 
 def check_servers_count(real, expected):
-     """Return a problem if the number of backend servers is different than expected."""
-     if real == 0:
-         return Problem(
-             message='Could not find any backend server',
-             severity=CRITICAL,
-         )
-     if real != expected:
-         return Problem(
-             message='{real} backend servers detected (expected {expected})'.format(
-                 real=real,
-                 expected=expected,
-             ),
-             severity=WARNING,
-         )
+    """Return a problem if the number of backend servers is different than expected."""
+    if real == 0:
+        return Problem(
+            message='Could not find any backend server',
+            severity=CRITICAL,
+        )
+    if real != expected:
+        return Problem(
+            message='{real} backend servers detected (expected {expected})'.format(
+                real=real,
+                expected=expected,
+            ),
+            severity=WARNING,
+        )
 
 
 def check_servers_no_master(servers):
     """Return a problem if no backend server has the status "Master"."""
-    if not any(['Master' in s.status for s in servers]):
+    if not any('Master' in s.status for s in servers):
         return Problem(
             message='No backend server in Master mode',
             severity=CRITICAL,
         )
-
     return None
 
 
@@ -206,19 +179,16 @@ def check_server_status(server):
             message='Server "{0}" in Maintenance mode'.format(server.name),
             severity=WARNING,
         )
-
     if 'Down' in server.status:
         return Problem(
             message='Server "{0}" down'.format(server.name),
             severity=WARNING,
         )
-
     if 'Synced' not in server.status:
         return Problem(
             message='Server "{0}" not Synced'.format(server.name),
             severity=CRITICAL,
         )
-
     return None
 
 
@@ -232,56 +202,43 @@ def check_server_connections(server, connections_threshold):
             ),
             severity=WARNING,
         )
-
     return None
 
 
 def check_sessions(sessions, sessions_threshold):
     problems = []
-
     problems.append(check_sessions_count(len(sessions), sessions_threshold))
     problems.append(check_sessions_unique_id(sessions))
-
     return [p for p in problems if p is not None]
 
 
-def check_sessions_count(real, max):
+def check_sessions_count(real, max_sessions):
     """Return a problem if the number of sessions is outside the "normal" range."""
-    if real > max:
+    if real > max_sessions:
         return Problem(
             message='{real} sessions detected (max {max})'.format(
                 real=real,
-                max=max,
+                max=max_sessions,
             ),
             severity=WARNING,
         )
-
     return None
 
 
 def check_sessions_unique_id(sessions):
-    """Alert if 2 sessions have the same ID.
-
-    From MaxScale documentation:
-    The sessions are referenced using ID values, these are actually memory address,
-    however the important thing is that no two session have the same ID.
-    """
-    # Compare list and set sizes. If they differ, there are duplicates
+    """Alert if 2 sessions have the same ID."""
     if len([s.id for s in sessions]) != len({s.id for s in sessions}):
         return Problem(
             message='Some sessions have the same ID',
             severity=WARNING,
         )
-
     return None
 
 
 def check_monitors(monitors):
     problems = []
-
     for monitor in monitors:
         problems.append(check_monitor_status(monitor))
-
     return [p for p in problems if p is not None]
 
 
@@ -292,7 +249,6 @@ def check_monitor_status(monitor):
             message='Status of monitor "{0}": {1}'.format(monitor.name, monitor.status),
             severity=WARNING,
         )
-
     return None
 
 
@@ -308,7 +264,6 @@ def print_message(problems):
         print('OK - No problem detected on MaxScale')
 
 
-# Those thresholds are just a guess, they are maybe way to low/high...
 DEFAULT_CONNECTIONS_THRESHOLD = 500
 DEFAULT_SESSIONS_THRESHOLD = 1000
 
@@ -347,5 +302,4 @@ if __name__ == '__main__':
         help='Print detailed information',
     )
     args = parser.parse_args()
-
     main(args)