handle slow qm commands better

src/pvecommon/__init__.py

@@ -1,8 +1,14 @@
 import time
 import random
 import pexpect
+import logging
 from functools import wraps
 
+from datetime import datetime, timedelta
+
+qm_monitor_defer_close = True
+deferred_closing = []
+
 global_qm_timeout = 10
 qm_max_ttl = 600
 qm_rand = 60
@@ -29,6 +35,7 @@ def ttl_cache_with_randomness(max_ttl, randomness_factor):
 
 @ttl_cache_with_randomness(qm_max_ttl, qm_rand)
 def qm_term_cmd(vm_id, cmd, timeout=global_qm_timeout):
+    global deferred_closing
     child = pexpect.spawn(f'qm monitor {vm_id}')
     try:
         child.expect('qm>', timeout=timeout)
@@ -36,6 +43,28 @@ def qm_term_cmd(vm_id, cmd, timeout=global_qm_timeout):
         child.expect('qm>', timeout=timeout)
         raw_output = child.before.decode('utf-8').strip()
     finally:
+        try:
             child.close()
+        except pexpect.exceptions.ExceptionPexpect:
+            if qm_monitor_defer_close:
+                logging.warn(f"Failed to close {vm_id=}, {cmd=}; deferring")
+                deferred_closing.append((child, datetime.now()))
+
+    if qm_monitor_defer_close:
+        # Reattempt closing deferred child processes
+        still_deferred = []
+        for child, timestamp in deferred_closing:
+            if datetime.now() - timestamp > timedelta(seconds=10):
+                try:
+                    child.close()
+                except pexpect.exceptions.ExceptionPexpect:
+                    still_deferred.append((child, timestamp))
+            else:
+                still_deferred.append((child, timestamp))
+
+        deferred_closing = still_deferred
+
+        if deferred_closing:
+            raise Exception("Could not terminate some child processes after 10 seconds.")
 
     return raw_output

src/pvemon/__init__.py

@@ -203,6 +203,7 @@ def main():
     parser.add_argument('--qm-terminal-timeout', type=int, default=10, help='timeout for qm terminal commands')
     parser.add_argument('--qm-max-ttl', type=int, default=600, help='cache ttl for data pulled from qm monitor')
     parser.add_argument('--qm-rand', type=int, default=60, help='randomize qm monitor cache expiry')
+    parser.add_argument('--qm-monitor-defer-close', type=str, default="true", help='defer and retry closing unresponsive qm monitor sessions')
 
     args = parser.parse_args()
 
@@ -216,6 +217,7 @@ def main():
     pvecommon.global_qm_timeout = args.qm_terminal_timeout
     pvecommon.qm_max_ttl = args.qm_max_ttl
     pvecommon.qm_rand = args.qm_rand
+    pvecommon.qm_monitor_defer_close = args.qm_monitor_defer_close
 
     for name, description, labels in gauge_settings:
         gauge_dict[name] = Gauge(f"{prefix}_{name}", description, labels)