diff --git a/interface.yaml b/interface.yaml
index edd0c90..f03f3d7 100644
--- a/interface.yaml
+++ b/interface.yaml
@@ -11,3 +11,6 @@ ignore:
   - 'tox.ini'
   - 'unit_tests'
   - '.zuul.yaml'
+  - 'setup.cfg'
+  - 'setup.py'
+  - '**/ops_ha_interface.py'
diff --git a/interface_hacluster/__init__.py b/interface_hacluster/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/interface_hacluster/ops_ha_interface.py b/interface_hacluster/ops_ha_interface.py
new file mode 100644
index 0000000..cfad252
--- /dev/null
+++ b/interface_hacluster/ops_ha_interface.py
@@ -0,0 +1,123 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# Copyright 2021 Ubuntu
+# See LICENSE file for licensing details.
+
+import hashlib
+import json
+import interface_hacluster.common as common
+
+from ops.framework import (
+    StoredState,
+    EventBase,
+    ObjectEvents,
+    EventSource,
+    Object)
+
+
+class HAServiceReadyEvent(EventBase):
+    pass
+
+
+class HAServiceEvents(ObjectEvents):
+    ha_ready = EventSource(HAServiceReadyEvent)
+
+
+class HAServiceRequires(Object, common.ResourceManagement):
+
+    on = HAServiceEvents()
+    _stored = StoredState()
+
+    def __init__(self, charm, relation_name):
+        super().__init__(charm, relation_name)
+        self.relation_name = relation_name
+        self.framework.observe(
+            charm.on[self.relation_name].relation_changed,
+            self._on_relation_changed)
+        self._stored.set_default(
+            resources={})
+
+    def get_local(self, key, default=None):
+        key = '%s.%s' % ('local-data', key)
+        json_value = getattr(self._stored, key, None)
+        if json_value:
+            return json.loads(json_value)
+        if default:
+            return default
+        return None
+
+    def set_local(self, key=None, value=None, data=None, **kwdata):
+        if data is None:
+            data = {}
+        if key is not None:
+            data[key] = value
+        data.update(kwdata)
+        if not data:
+            return
+        for k, v in data.items():
+            setattr(
+                self._stored,
+                'local-data.{}'.format(k),
+                json.dumps(v))
+
+    def _on_relation_changed(self, event):
+        if self.is_clustered():
+            self.on.ha_ready.emit()
+
+    def data_changed(self, data_id, data, hash_type='md5'):
+        """Check if the given set of data has changed since the previous call.
+
+        This works by hashing the JSON-serialization of the data.  Note that,
+        while the data will be serialized using ``sort_keys=True``, some types
+        of data structures, such as sets, may lead to false positivies.
+
+        NOTE: This method is adapted from the charms.reactive framework and
+        is used by the parent class `common.ResourceManagement`. It is unlikely
+        that a charm utilising this interface would call this method directly.
+
+        :param str data_id: Unique identifier for this set of data.
+        :param data: JSON-serializable data.
+        :param str hash_type: Any hash algorithm supported by :mod:`hashlib`.
+        """
+        key = 'data_changed.%s' % data_id
+        alg = getattr(hashlib, hash_type)
+        serialized = json.dumps(data, sort_keys=True).encode('utf8')
+        old_hash = self.get_local(key)
+        new_hash = alg(serialized).hexdigest()
+        self.set_local(key, new_hash)
+        return old_hash != new_hash
+
+    def set_remote(self, key=None, value=None, data=None, **kwdata):
+        if data is None:
+            data = {}
+        if key is not None:
+            data[key] = value
+        data.update(kwdata)
+        if not data:
+            return
+        for relation in self.framework.model.relations[self.relation_name]:
+            for k, v in data.items():
+                # The reactive framework copes with integer values but the ops
+                # framework insists on strings so convert them.
+                if isinstance(v, int):
+                    v = str(v)
+                relation.data[self.model.unit][k] = v
+
+    def get_remote_all(self, key, default=None):
+        """Return a list of all values presented by remote units for key"""
+        values = []
+        for relation in self.framework.model.relations[self.relation_name]:
+            for unit in relation.units:
+                value = relation.data[unit].get(key)
+                if value:
+                    values.append(value)
+        return list(set(values))
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..73e2f7c
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,18 @@
+[metadata]
+name = interface_hacluster
+summary = Charm interface for Hacluster using Operator Framework
+version = 0.0.1.dev1
+description-file =
+    README.rst
+author = OpenStack Charmers
+author-email = openstack-charmers@lists.ubuntu.com
+url = https://github.com/openstack/charm-interface-hacluster.git
+classifier =
+    Development Status :: 2 - Pre-Alpha
+    Intended Audience :: Developers
+    Topic :: System
+    Topic :: System :: Installation/Setup
+    opic :: System :: Software Distribution
+    Programming Language :: Python :: 3
+    Programming Language :: Python :: 3.5
+    License :: OSI Approved :: Apache Software License
diff --git a/setup.py b/setup.py
new file mode 100644
index 0000000..d41471d
--- /dev/null
+++ b/setup.py
@@ -0,0 +1,38 @@
+# -*- coding: utf-8 -*-
+
+# Copyright 2021 Canonical Ltd.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Module used to setup the interface_hacluster framework."""
+
+from __future__ import print_function
+
+from setuptools import setup, find_packages
+
+version = "0.0.1.dev1"
+install_require = [
+    'charmhelpers',
+    'ops',
+]
+
+tests_require = [
+    'tox >= 2.3.1',
+]
+
+setup(
+    license='Apache-2.0: http://www.apache.org/licenses/LICENSE-2.0',
+    packages=find_packages(exclude=["unit_tests"]),
+    zip_safe=False,
+    install_requires=install_require,
+)
diff --git a/test-requirements.txt b/test-requirements.txt
index 6da7df2..12452e5 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -4,3 +4,4 @@ stestr>=2.2.0
 charms.reactive
 coverage>=3.6
 netifaces
+git+https://github.com/canonical/operator.git#egg=ops
diff --git a/unit_tests/test_ops.py b/unit_tests/test_ops.py
new file mode 100644
index 0000000..306968d
--- /dev/null
+++ b/unit_tests/test_ops.py
@@ -0,0 +1,158 @@
+#!/usr/bin/env python3
+
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# Copyright 2021 Ubuntu
+# See LICENSE file for licensing details.
+
+import unittest
+import sys
+sys.path.append('.')  # noqa
+from ops.testing import Harness
+from ops.charm import CharmBase
+import interface_hacluster.ops_ha_interface as ops_ha_interface
+
+
+class HAServiceRequires(unittest.TestCase):
+
+    class MyCharm(CharmBase):
+
+        def __init__(self, *args):
+            super().__init__(*args)
+            self.seen_events = []
+            self.ha = ops_ha_interface.HAServiceRequires(self, 'ha')
+
+            self.framework.observe(
+                self.ha.on.ha_ready,
+                self._log_event)
+
+        def _log_event(self, event):
+            self.seen_events.append(type(event).__name__)
+
+    def setUp(self):
+        super().setUp()
+        self.harness = Harness(
+            self.MyCharm,
+            meta='''
+name: my-charm
+requires:
+  ha:
+    interface: hacluster
+    scope: container
+'''
+        )
+
+    def test_local_vars(self):
+        self.harness.begin()
+        self.harness.charm.ha.set_local('a', 'b')
+        self.assertEqual(
+            self.harness.charm.ha.get_local('a'),
+            'b')
+        self.harness.charm.ha.set_local(**{'c': 'd', 'e': 'f'})
+        self.assertEqual(
+            self.harness.charm.ha.get_local('c'),
+            'd')
+        self.assertEqual(
+            self.harness.charm.ha.get_local('e'),
+            'f')
+        self.harness.charm.ha.set_local(data={'g': 'h', 'i': 'j'})
+        self.assertEqual(
+            self.harness.charm.ha.get_local('g'),
+            'h')
+        self.assertEqual(
+            self.harness.charm.ha.get_local('i'),
+            'j')
+
+    def test_remote_vars(self):
+        self.harness.begin()
+        rel_id = self.harness.add_relation(
+            'ha',
+            'hacluster')
+        self.harness.add_relation_unit(
+            rel_id,
+            'hacluster/0')
+        self.harness.charm.ha.set_remote('a', 'b')
+        rel_data = self.harness.get_relation_data(
+            rel_id,
+            'my-charm/0')
+        self.assertEqual(rel_data, {'a': 'b'})
+
+    def test_get_remote_all(self):
+        self.harness.begin()
+        rel_id1 = self.harness.add_relation(
+            'ha',
+            'hacluster-a')
+        self.harness.add_relation_unit(
+            rel_id1,
+            'hacluster-a/0')
+        self.harness.update_relation_data(
+            rel_id1,
+            'hacluster-a/0',
+            {'fruit': 'banana'})
+        self.harness.add_relation_unit(
+            rel_id1,
+            'hacluster-a/1')
+        self.harness.update_relation_data(
+            rel_id1,
+            'hacluster-a/1',
+            {'fruit': 'orange'})
+        rel_id2 = self.harness.add_relation(
+            'ha',
+            'hacluster-b')
+        self.harness.add_relation_unit(
+            rel_id2,
+            'hacluster-b/0')
+        self.harness.update_relation_data(
+            rel_id2,
+            'hacluster-b/0',
+            {'fruit': 'grape'})
+        self.harness.add_relation_unit(
+            rel_id2,
+            'hacluster-b/1')
+        self.harness.update_relation_data(
+            rel_id2,
+            'hacluster-b/1',
+            {'veg': 'carrot'})
+        self.assertEqual(
+            self.harness.charm.ha.get_remote_all('fruit'),
+            ['orange', 'grape', 'banana'])
+
+    def test_ha_ready(self):
+        self.harness.begin()
+        self.assertEqual(
+            self.harness.charm.seen_events,
+            [])
+        rel_id = self.harness.add_relation(
+            'ha',
+            'hacluster')
+        self.harness.add_relation_unit(
+            rel_id,
+            'hacluster/0')
+        self.harness.update_relation_data(
+            rel_id,
+            'hacluster/0',
+            {'clustered': 'yes'})
+        self.assertEqual(
+            self.harness.charm.seen_events,
+            ['HAServiceReadyEvent'])
+
+    def test_data_changed(self):
+        self.harness.begin()
+        self.assertTrue(
+            self.harness.charm.ha.data_changed(
+                'relation-data', {'a': 'b'}))
+        self.assertFalse(
+            self.harness.charm.ha.data_changed(
+                'relation-data', {'a': 'b'}))
+        self.assertTrue(
+            self.harness.charm.ha.data_changed(
+                'relation-data', {'a': 'c'}))