add cache for qm monitor functions

src/pvecommon/__init__.py

@@ -1,7 +1,33 @@
+import time
+import random
 import pexpect
+from functools import wraps
 
 global_qm_timeout = 10
+qm_max_ttl = 600
+qm_rand = 60
 
+def ttl_cache_with_randomness(max_ttl, randomness_factor):
+    cache = {}
+    def decorator(func):
+        @wraps(func)
+        def wrapper(*args, **kwargs):
+            # Create a key based on the args and kwargs
+            key = str(args) + str(kwargs)
+            # Check if the key is in the cache and not expired
+            if key in cache:
+                result, timestamp = cache[key]
+                elapsed_time = time.time() - timestamp
+                if elapsed_time < max_ttl + random.uniform(-randomness_factor, randomness_factor):
+                    return result
+            # Call the actual function and store the result in cache
+            result = func(*args, **kwargs)
+            cache[key] = (result, time.time())
+            return result
+        return wrapper
+    return decorator
+
+@ttl_cache_with_randomness(qm_max_ttl, qm_rand)
 def qm_term_cmd(vm_id, cmd, timeout=global_qm_timeout):
     child = pexpect.spawn(f'qm monitor {vm_id}')
     try:

src/pvemon/__init__.py

@@ -199,6 +199,8 @@ def main():
     parser.add_argument('--loglevel', type=str, default='INFO', help='Set log level (DEBUG, INFO, WARNING, ERROR, CRITICAL)')
     parser.add_argument('--profile', type=str, default='false', help='collect metrics once, and print profiling stats')
     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')
 
     args = parser.parse_args()
 
@@ -210,6 +212,8 @@ def main():
     global prefix
     prefix = args.metrics_prefix
     pvecommon.global_qm_timeout = args.qm_terminal_timeout
+    pvecommon.qm_max_ttl = args.qm_max_ttl
+    pvecommon.qm_rand = args.qm_rand
 
     for name, description, labels in gauge_settings:
         gauge_dict[name] = Gauge(f"{prefix}_{name}", description, labels)

src/setup.py

@@ -2,7 +2,7 @@ from setuptools import setup, find_packages
 
 setup(
     name='pvemon',
-    version='1.0.1',
+    version = "1.0.1",
     packages=find_packages(),
     entry_points={
         'console_scripts': [