1 files changed, 57 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..b316151e7
--- /dev/null
+++ b/src/pybind/mgr/dashboard/plugins/ttl_cache.py
@@ -0,0 +1,57 @@
+"""
+This is a minimal implementation of TTL-ed lru_cache function.
+
+Based on Python 3 functools and backports.functools_lru_cache.
+"""
+from __future__ import absolute_import
+
+from collections import OrderedDict
+from functools import wraps
+from threading import RLock
+from time import time
+
+try:
+    from typing import Tuple
+except ImportError:
+    pass  # For typing only
+
+
+def ttl_cache(ttl, maxsize=128, typed=False):
+    if typed is not False:
+        raise NotImplementedError("typed caching not supported")
+
+    def decorating_function(function):
+        cache = OrderedDict()  # type: OrderedDict[object, Tuple[bool, float]]
+        stats = [0, 0, 0]
+        rlock = RLock()
+        setattr(function, 'cache_info', lambda:
+                "hits={}, misses={}, expired={}, maxsize={}, currsize={}".format(
+                    stats[0], stats[1], stats[2], maxsize, len(cache)))
+
+        @wraps(function)
+        def wrapper(*args, **kwargs):
+            key = args + tuple(kwargs.items())
+            with rlock:
+                refresh = True
+                if key in cache:
+                    (ret, ts) = cache[key]
+                    del cache[key]
+                    if time() - ts < ttl:
+                        refresh = False
+                        stats[0] += 1
+                    else:
+                        stats[2] += 1
+
+                if refresh:
+                    ret = function(*args, **kwargs)
+                    ts = time()
+                    if len(cache) == maxsize:
+                        cache.popitem(last=False)
+                    stats[1] += 1
+
+                cache[key] = (ret, ts)
+
+            return ret
+
+        return wrapper
+    return decorating_function