diff --git a/charms/reactive/bus.py b/charms/reactive/bus.py
index 885e498..853571a 100644
--- a/charms/reactive/bus.py
+++ b/charms/reactive/bus.py
@@ -229,6 +229,7 @@ class Handler(object):
         self._action = action
         self._args = []
         self._predicates = []
+        self._post_callbacks = []
         self._states = set()
 
     def id(self):
@@ -255,6 +256,12 @@ class Handler(object):
             hookenv.log('  Adding predicate for %s: %s' % (self.id(), _predicate), level=hookenv.DEBUG)
         self._predicates.append(predicate)
 
+    def add_post_callback(self, callback):
+        """
+        Add a callback to be run after the action is invoked.
+        """
+        self._post_callbacks.append(callback)
+
     def test(self):
         """
         Check the predicate(s) and return True if this handler should be invoked.
@@ -278,6 +285,8 @@ class Handler(object):
         """
         args = self._get_args()
         self._action(*args)
+        for callback in self._post_callbacks:
+            callback()
 
     def register_states(self, states):
         """
diff --git a/charms/reactive/decorators.py b/charms/reactive/decorators.py
index 7918106..e89332f 100644
--- a/charms/reactive/decorators.py
+++ b/charms/reactive/decorators.py
@@ -205,18 +205,18 @@ def not_unless(*desired_states):
     return _decorator
 
 
-def only_once(action):
+def only_once(action=None):
     """
-    Ensure that the decorated function is only executed the first time it is called.
+    Register the decorated function to be run once, and only once.
 
-    This can be used on reactive handlers to ensure that they are only triggered
-    once, even if their conditions continue to match on subsequent calls, even
-    across hook invocations.
+    This decorator will never cause arguments to be passed to the handler.
     """
-    @wraps(action)
-    def wrapper(*args, **kwargs):
-        action_id = _action_id(action)
-        if not was_invoked(action_id):
-            action(*args, **kwargs)
-            mark_invoked(action_id)
-    return wrapper
+    if action is None:
+        # allow to be used as @only_once or @only_once()
+        return only_once
+
+    action_id = _action_id(action)
+    handler = Handler.get(action)
+    handler.add_predicate(lambda: not was_invoked(action_id))
+    handler.add_post_callback(partial(mark_invoked, action_id))
+    return action

only_once help unclear
_From @jacekn on January 27, 2016 17:29_

I was trying to execute certain function only once in my code.

This does not work:
```
@only_once()
def basenode():
    print("in basenode")
```
```
TypeError: only_once() missing 1 required positional argument: 'action'
```

I tried like this but it also did not work:
```
@only_once("basenode")
def basenode():
    print("in basenode")
```
```
AttributeError: 'str' object has no attribute '__code__'
```
Can documentation be clarified to show correct use of this decorator?

_Copied from original issue: juju/charm-tools#94_
diff --git a/tests/test_decorators.py b/tests/test_decorators.py
index 4691a30..2599b53 100644
--- a/tests/test_decorators.py
+++ b/tests/test_decorators.py
@@ -241,11 +241,28 @@ class TestReactiveDecorators(unittest.TestCase):
         calls = []
 
         @reactive.decorators.only_once
-        def test(num):
-            calls.append(num)
+        def test():
+            calls.append(len(calls)+1)
+
+        handler = reactive.bus.Handler.get(test)
 
-        test(1)
-        test(2)
+        assert handler.test()
+        handler.invoke()
+        assert not handler.test()
+        self.assertEquals(calls, [1])
+
+    def test_only_once_parens(self):
+        calls = []
+
+        @reactive.decorators.only_once()
+        def test():
+            calls.append(len(calls)+1)
+
+        handler = reactive.bus.Handler.get(test)
+
+        assert handler.test()
+        handler.invoke()
+        assert not handler.test()
         self.assertEquals(calls, [1])
 
     def test_multi(self):

pip install -e .
parse_log_pytest
requirements.txt
coverage mock nose flake8 ipython ipdb pytest
3.6
requirements.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
attrs==22.2.0
backcall==0.2.0
certifi==2021.5.30
charmhelpers==1.2.1
-e git+https://github.com/juju-solutions/charms.reactive.git@04663e45f3683d4c497f43526d3ac26593ee10a2#egg=charms.reactive
coverage==6.2
decorator==5.1.1
flake8==5.0.4
importlib-metadata==4.2.0
importlib-resources==5.4.0
iniconfig==1.1.1
ipdb==0.13.13
ipython==7.16.3
ipython-genutils==0.2.0
jedi==0.17.2
Jinja2==3.0.3
MarkupSafe==2.0.1
mccabe==0.7.0
mock==5.2.0
netaddr==0.10.1
nose==1.3.7
packaging==21.3
parso==0.7.1
pbr==6.1.1
pexpect==4.9.0
pickleshare==0.7.5
pluggy==1.0.0
prompt-toolkit==3.0.36
ptyprocess==0.7.0
py==1.11.0
pyaml==23.5.8
pycodestyle==2.9.1
pyflakes==2.5.0
Pygments==2.14.0
pyparsing==3.1.4
pytest==7.0.1
PyYAML==6.0.1
six==1.17.0
tomli==1.2.3
traitlets==4.3.3
typing_extensions==4.1.1
wcwidth==0.2.13
zipp==3.6.0

name: charms.reactive
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - pip=21.2.2=py36h06a4308_0
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - attrs==22.2.0
      - backcall==0.2.0
      - charmhelpers==1.2.1
      - coverage==6.2
      - decorator==5.1.1
      - flake8==5.0.4
      - importlib-metadata==4.2.0
      - importlib-resources==5.4.0
      - iniconfig==1.1.1
      - ipdb==0.13.13
      - ipython==7.16.3
      - ipython-genutils==0.2.0
      - jedi==0.17.2
      - jinja2==3.0.3
      - markupsafe==2.0.1
      - mccabe==0.7.0
      - mock==5.2.0
      - netaddr==0.10.1
      - nose==1.3.7
      - packaging==21.3
      - parso==0.7.1
      - pbr==6.1.1
      - pexpect==4.9.0
      - pickleshare==0.7.5
      - pluggy==1.0.0
      - prompt-toolkit==3.0.36
      - ptyprocess==0.7.0
      - py==1.11.0
      - pyaml==23.5.8
      - pycodestyle==2.9.1
      - pyflakes==2.5.0
      - pygments==2.14.0
      - pyparsing==3.1.4
      - pytest==7.0.1
      - pyyaml==6.0.1
      - six==1.17.0
      - tomli==1.2.3
      - traitlets==4.3.3
      - typing-extensions==4.1.1
      - wcwidth==0.2.13
      - zipp==3.6.0
prefix: /opt/conda/envs/charms.reactive

tests/test_decorators.py::TestReactiveDecorators::test_only_once tests/test_decorators.py::TestReactiveDecorators::test_only_once_parens
tests/test_decorators.py::TestReactiveDecorators::test_hook tests/test_decorators.py::TestReactiveDecorators::test_multi tests/test_decorators.py::TestReactiveDecorators::test_not_unless tests/test_decorators.py::TestReactiveDecorators::test_when tests/test_decorators.py::TestReactiveDecorators::test_when_all tests/test_decorators.py::TestReactiveDecorators::test_when_any tests/test_decorators.py::TestReactiveDecorators::test_when_file_changed tests/test_decorators.py::TestReactiveDecorators::test_when_none tests/test_decorators.py::TestReactiveDecorators::test_when_not tests/test_decorators.py::TestReactiveDecorators::test_when_not_all
charms/reactive/bus.py charms/reactive/decorators.py
charms/reactive/bus.py charms/reactive/decorators.py