Use the instance service key for registry JWT signing

util/expiresdict.py

@@ -0,0 +1,55 @@
+from datetime import datetime
+
+class ExpiresEntry(object):
+  """ A single entry under a ExpiresDict. """
+  def __init__(self, value, expires=None):
+    self.value = value
+    self._expiration = expires
+
+  @property
+  def expired(self):
+    if self._expiration is None:
+      return False
+
+    return datetime.now() >= self._expiration
+
+
+class ExpiresDict(object):
+  """ ExpiresDict defines a dictionary-like class whose keys have expiration. The rebuilder is
+      a function that returns the full contents of the cached dictionary as a dict of the keys
+      and whose values are TTLEntry's.
+  """
+  def __init__(self, rebuilder):
+    self._rebuilder = rebuilder
+    self._items = {}
+
+  def __getitem__(self, key):
+    found = self.get(key)
+    if found is None:
+      raise KeyError
+
+    return found
+
+  def get(self, key, default_value=None):
+    # Check the cache first. If the key is found and it has not yet expired,
+    # return it.
+    found = self._items.get(key)
+    if found is not None and not found.expired:
+      return found.value
+
+    # Otherwise the key has expired or was not found. Rebuild the cache and check it again.
+    self._rebuild()
+    found = self._items.get(key)
+    if found is None:
+      return default_value
+
+    return found.value
+
+  def __contains__(self, key):
+    return self.get(key) is not None
+
+  def _rebuild(self):
+    self._items = self._rebuilder()
+
+  def set(self, key, value, expires=None):
+    self._items[key] = ExpiresEntry(value, expires=expires)