1 files changed, 119 insertions, 0 deletions
diff --git a/src/pybind/mgr/dashboard/plugins/ttl_cache.py b/src/pybind/mgr/dashboard/plugins/ttl_cache.py
new file mode 100644
index 000000000..78221547a
--- /dev/null
+++ b/src/pybind/mgr/dashboard/plugins/ttl_cache.py
@@ -0,0 +1,119 @@
+"""
+This is a minimal implementation of TTL-ed lru_cache function.
+
+Based on Python 3 functools and backports.functools_lru_cache.
+"""
+
+import os
+from collections import OrderedDict
+from functools import wraps
+from threading import RLock
+from time import time
+from typing import Any, Dict
+
+try:
+    from typing import Tuple
+except ImportError:
+    pass  # For typing only
+
+
+class TTLCache:
+    class CachedValue:
+        def __init__(self, value, timestamp):
+            self.value = value
+            self.timestamp = timestamp
+
+    def __init__(self, reference, ttl, maxsize=128):
+        self.reference = reference
+        self.ttl: int = ttl
+        self.maxsize = maxsize
+        self.cache: OrderedDict[Tuple[Any], TTLCache.CachedValue] = OrderedDict()
+        self.hits = 0
+        self.misses = 0
+        self.expired = 0
+        self.rlock = RLock()
+
+    def __getitem__(self, key):
+        with self.rlock:
+            if key not in self.cache:
+                self.misses += 1
+                raise KeyError(f'"{key}" is not set')
+
+            cached_value = self.cache[key]
+            if time() - cached_value.timestamp >= self.ttl:
+                del self.cache[key]
+                self.expired += 1
+                self.misses += 1
+                raise KeyError(f'"{key}" is not set')
+
+            self.hits += 1
+            return cached_value.value
+
+    def __setitem__(self, key, value):
+        with self.rlock:
+            if key in self.cache:
+                cached_value = self.cache[key]
+                if time() - cached_value.timestamp >= self.ttl:
+                    self.expired += 1
+            if len(self.cache) == self.maxsize:
+                self.cache.popitem(last=False)
+
+            self.cache[key] = TTLCache.CachedValue(value, time())
+
+    def clear(self):
+        with self.rlock:
+            self.cache.clear()
+
+    def info(self) -> str:
+        return (f'cache={self.reference} hits={self.hits}, misses={self.misses},'
+                f'expired={self.expired}, maxsize={self.maxsize}, currsize={len(self.cache)}')
+
+
+class CacheManager:
+    caches: Dict[str, TTLCache] = {}
+
+    @classmethod
+    def get(cls, reference: str, ttl=30, maxsize=128):
+        if reference in cls.caches:
+            return cls.caches[reference]
+        cls.caches[reference] = TTLCache(reference, ttl, maxsize)
+        return cls.caches[reference]
+
+
+def ttl_cache(ttl, maxsize=128, typed=False, label: str = ''):
+    if typed is not False:
+        raise NotImplementedError("typed caching not supported")
+
+    # disable caching while running unit tests
+    if 'UNITTEST' in os.environ:
+        ttl = 0
+
+    def decorating_function(function):
+        cache_name = label
+        if not cache_name:
+            cache_name = function.__name__
+        cache = CacheManager.get(cache_name, ttl, maxsize)
+
+        @wraps(function)
+        def wrapper(*args, **kwargs):
+            key = args + tuple(kwargs.items())
+            try:
+                return cache[key]
+            except KeyError:
+                ret = function(*args, **kwargs)
+                cache[key] = ret
+                return ret
+
+        return wrapper
+    return decorating_function
+
+
+def ttl_cache_invalidator(label: str):
+    def decorating_function(function):
+        @wraps(function)
+        def wrapper(*args, **kwargs):
+            ret = function(*args, **kwargs)
+            CacheManager.get(label).clear()
+            return ret
+        return wrapper
+    return decorating_function