Merge ~jk0ne/charm-k8s-discourse/+git/charm-k8s-discourse:charmcraft-review2 into ~discourse-charmers/charm-k8s-discourse/+git/charmcraft-review:master

[Jay Kuri]

Complete discourse charm ready for review.

[Facundo Batista (facundo)]

It looks great! Approved, but check a small suggestion in an inline comment.

review: Approve

08fde17... by Jay Kuri on 2020-11-02

Fix up non-leader event handling and fix missing field check per review

[Tom Haddon (mthaddon)]

One comment inline

80ff3cc... by Jay Kuri on 2020-11-03

Tweak missing_field check - remove parens

[Tom Haddon (mthaddon)]

I'm going to mark this as "Merged" as we want to get this off the review board for MPs for this project. We'll be incorporating the changes from this MP into a new MP against the main charm code.

diff --git a/image/Dockerfile b/image/Dockerfile
index 7baf5cb..96d49df 100644
--- a/image/Dockerfile
+++ b/image/Dockerfile
@@ -13,7 +13,7 @@ ARG CONTAINER_APP_GID
 
 # Copy any args we got into the environment.
 ENV CONTAINER_APP_NAME ${CONTAINER_APP_NAME:-discourse}
-ENV CONTAINER_APP_VERSION ${CONTAINER_APP_VERSION:-v2.4.3}
+ENV CONTAINER_APP_VERSION ${CONTAINER_APP_VERSION:-v2.5.2}
 ENV CONTAINER_APP_USERNAME ${CONTAINER_APP_USERNAME:-discourse}
 ENV CONTAINER_APP_UID ${CONTAINER_APP_UID:-200}
 ENV CONTAINER_APP_GROUP ${CONTAINER_APP_GROUP:-discourse}
diff --git a/src/charm.py b/src/charm.py
index a16d636..5bb75ad 100755
--- a/src/charm.py
+++ b/src/charm.py
@@ -2,37 +2,258 @@
 # Copyright 2020 Canonical Ltd.
 # See LICENSE file for licensing details.
 
-import logging
-
+import ops.lib
 from ops.charm import CharmBase
 from ops.main import main
 from ops.framework import StoredState
 
-logger = logging.getLogger(__name__)
+from ops.model import ActiveStatus, BlockedStatus, MaintenanceStatus
+
+
+pgsql = ops.lib.use("pgsql", 1, "[e-mail]")
+
+
+def create_discourse_pod_config(config):
+    """Create the pod environment config from the juju config."""
+    pod_config = {
+        'DISCOURSE_POSTGRES_USERNAME': config['db_user'],
+        'DISCOURSE_POSTGRES_PASSWORD': config['db_password'],
+        'DISCOURSE_POSTGRES_HOST': config['db_host'],
+        'DISCOURSE_POSTGRES_NAME': config['db_name'],
+        'DISCOURSE_DEVELOPER_EMAILS': config['developer_emails'],
+        'DISCOURSE_HOSTNAME': config['external_hostname'],
+        'DISCOURSE_SMTP_DOMAIN': config['smtp_domain'],
+        'DISCOURSE_SMTP_ADDRESS': config['smtp_address'],
+        'DISCOURSE_SMTP_PORT': config['smtp_port'],
+        'DISCOURSE_SMTP_AUTHENTICATION': config['smtp_authentication'],
+        'DISCOURSE_SMTP_OPENSSL_VERIFY_MODE': config['smtp_openssl_verify_mode'],
+        'DISCOURSE_SMTP_USER_NAME': config['smtp_username'],
+        'DISCOURSE_SMTP_PASSWORD': config['smtp_password'],
+        'DISCOURSE_REDIS_HOST': config['redis_host'],
+        'DISCOURSE_ENABLE_CORS': config['enable_cors'],
+        'DISCOURSE_CORS_ORIGIN': config['cors_origin'],
+    }
+    return pod_config
+
+
+def create_ingress_config(app_name, config):
+    """Create the ingress config form the juju config."""
+    annotations = {}
+    ingressResource = {
+        "name": app_name + "-ingress",
+        "spec": {
+            "rules": [
+                {
+                    "host": config['external_hostname'],
+                    "http": {"paths": [{"path": "/", "backend": {"serviceName": app_name, "servicePort": 3000}}]},
+                }
+            ]
+        },
+    }
+    tls_secret_name = config.get('tls_secret_name')
+    if tls_secret_name:
+        ingressResource['spec']['tls'] = [{'hosts': config['external_hostname'], 'secretName': tls_secret_name}]
+    else:
+        annotations['nginx.ingress.kubernetes.io/ssl-redirect'] = 'false'
+
+    if annotations:
+        ingressResource['annotations'] = annotations
+
+    return ingressResource
+
+
+def get_pod_spec(app_name, config):
+    """Get the entire pod spec using the juju config.
+
+    - uses create_discourse_pod_config() to generate pod envConfig.
+
+    - uses create_ingress_config() to generate pod ingressResources.
+
+    """
+    pod_spec = {
+        "version": 3,
+        "containers": [
+            {
+                "name": app_name,
+                "imageDetails": {"imagePath": config['discourse_image']},
+                "imagePullPolicy": "IfNotPresent",
+                "ports": [{"containerPort": 3000, "protocol": "TCP"}],
+                "envConfig": create_discourse_pod_config(config),
+                "kubernetes": {
+                    "readinessProbe": {
+                        "httpGet": {
+                            "path": "/srv/status",
+                            "port": 3000,
+                        }
+                    }
+                },
+            }
+        ],
+        "kubernetesResources": {"ingressResources": [create_ingress_config(app_name, config)]},
+    }
+    # This handles when we are trying to get an image from a private
+    # registry.
+    if config['image_user'] and config['image_pass']:
+        pod_spec['containers'][0]['imageDetails']['username'] = config['image_user']
+        pod_spec['containers'][0]['imageDetails']['password'] = config['image_pass']
+
+    return pod_spec
+
+
+def check_for_config_problems(config):
+    """Check if there are issues with the juju config.
+
+    - Primarily looks for missing config options using check_for_missing_config_fields()
+
+    - Returns a list of errors if any were found.
+    """
+    errors = []
+    missing_fields = check_for_missing_config_fields(config)
+
+    if missing_fields:
+        errors.append('Required configuration missing: {}'.format(" ".join(missing_fields)))
+
+    if "db_host" not in config or config["db_host"] is None:
+        errors.append("db relation is required")
+
+    return errors
+
+
+def check_for_missing_config_fields(config):
+    """Check for missing fields in juju config.
 
+    - Returns a list of required fields that are either not present
+      or are empty.
+    """
+    missing_fields = []
 
-class CharmK8SDiscourseCharm(CharmBase):
-    _stored = StoredState()
+    needed_fields = [
+        'db_name',
+        'smtp_address',
+        'redis_host',
+        'cors_origin',
+        'developer_emails',
+        'smtp_domain',
+        'discourse_image',
+        'external_hostname',
+    ]
+    for key in needed_fields:
+        if not config.get(key):
+            missing_fields.append(key)
+
+    return sorted(missing_fields)
+
+
+class DiscourseCharm(CharmBase):
+    stored = StoredState()
 
     def __init__(self, *args):
+        """Initialization.
+
+        - Primarily sets up defaults and event handlers.
+
+        """
         super().__init__(*args)
-        self.framework.observe(self.on.config_changed, self._on_config_changed)
-        self.framework.observe(self.on.fortune_action, self._on_fortune_action)
-        self._stored.set_default(things=[])
-
-    def _on_config_changed(self, _):
-        current = self.model.config["thing"]
-        if current not in self._stored.things:
-            logger.debug("found a new thing: %r", current)
-            self._stored.things.append(current)
-
-    def _on_fortune_action(self, event):
-        fail = event.params["fail"]
-        if fail:
-            event.fail(fail)
+
+        # TODO: is_started is unused. Remove?
+        self.stored.set_default(is_started=False, db_user=None, db_password=None, db_host=None)
+        self.framework.observe(self.on.leader_elected, self.configure_pod)
+        self.framework.observe(self.on.config_changed, self.configure_pod)
+        self.framework.observe(self.on.upgrade_charm, self.configure_pod)
+
+        self.db = pgsql.PostgreSQLClient(self, 'db')
+        self.framework.observe(self.db.on.database_relation_joined, self.on_database_relation_joined)
+        self.framework.observe(self.db.on.master_changed, self.on_database_changed)
+
+    def check_config_is_valid(self, config):
+        """Check that the provided config is valid.
+
+        - Returns True if config is valid, False otherwise.
+
+        - Sets model status as appropriate.
+        """
+        valid_config = True
+        errors = check_for_config_problems(config)
+
+        # Set status if we have a bad config.
+        if errors:
+            self.model.unit.status = BlockedStatus(", ".join(errors))
+            valid_config = False
+        else:
+            self.model.unit.status = MaintenanceStatus("Configuration passed validation")
+
+        return valid_config
+
+    def configure_pod(self, event=None):
+        """Configure pod.
+
+        - Verifies config is valid and unit is leader.
+
+        - Configures pod using pod_spec generated from config.
+        """
+        # Set our status while we get configured.
+        self.model.unit.status = MaintenanceStatus('Configuring pod')
+
+        # Leader must set the pod spec.
+        if self.model.unit.is_leader():
+            # Merge our config and state into a single dict and set
+            # defaults here, because the helpers avoid dealing with
+            # the framework.
+            config = dict(self.model.config)
+            if not config["db_name"]:
+                config["db_name"] = self.app.name
+            config["db_user"] = self.stored.db_user
+            config["db_password"] = self.stored.db_password
+            config["db_host"] = self.stored.db_host
+            # Get our spec definition.
+            if self.check_config_is_valid(config):
+                # Get pod spec using our app name and config
+                pod_spec = get_pod_spec(self.framework.model.app.name, config)
+                # Set our pod spec.
+                self.model.pod.set_spec(pod_spec)
+                self.stored.is_started = True
+                self.model.unit.status = ActiveStatus()
         else:
-            event.set_results({"fortune": "A bug in the code is worth two in the documentation."})
+            self.stored.is_started = True
+            self.model.unit.status = ActiveStatus()
+
+    def on_database_relation_joined(self, event):
+        """Event handler for a newly joined database relation.
+
+        - Sets the event.database field on the database joined event.
+
+        - Required because setting the database name is only possible
+          from inside the event handler per https://github.com/canonical/ops-lib-pgsql/issues/2
+        """
+        # Per https://github.com/canonical/ops-lib-pgsql/issues/2,
+        # changing the setting in the config will not take effect,
+        # unless the relation is dropped and recreated.
+        if self.model.unit.is_leader():
+            event.database = self.model.config["db_name"]
+        elif event.database != self.model.config["db_name"]:
+            # Leader has not yet set requirements. Defer, in case this unit
+            # becomes leader and needs to perform that operation.
+            event.defer()
+            return
+
+    def on_database_changed(self, event):
+        """Event handler for database relation change.
+
+        - Sets our database parameters based on what was provided
+          in the relation event.
+        """
+        if event.master is None:
+            self.stored.db_user = None
+            self.stored.db_password = None
+            self.stored.db_host = None
+            return
+
+        self.stored.db_user = event.master.user
+        self.stored.db_password = event.master.password
+        self.stored.db_host = event.master.host
+
+        self.configure_pod()
 
 
-if __name__ == "__main__":
-    main(CharmK8SDiscourseCharm)
+if __name__ == '__main__':  # pragma: no cover
+    main(DiscourseCharm)
diff --git a/tests/unit/fixtures/config_invalid_missing_cors.yaml b/tests/unit/fixtures/config_invalid_missing_cors.yaml
new file mode 100644
index 0000000..da4a5c8
--- /dev/null
+++ b/tests/unit/fixtures/config_invalid_missing_cors.yaml
@@ -0,0 +1,20 @@
+config:
+    cors_origin: ''
+    db_name: discourse
+    db_host: 10.25.244.12
+    developer_emails: [e-mail]
+    discourse_image: discourse-k8s:1.0.7f
+    enable_cors: true
+    external_hostname: discourse.local
+    image_pass: ''
+    image_user: ''
+    redis_host: 10.9.89.197
+    smtp_address: 167.89.123.58
+    smtp_authentication: login
+    smtp_domain: example.com
+    smtp_openssl_verify_mode: none
+    smtp_password: OBV10USLYF4K3
+    smtp_port: 587
+    smtp_username: apikey
+missing_fields: 
+    - 'cors_origin'
diff --git a/tests/unit/fixtures/config_invalid_missing_db_name.yaml b/tests/unit/fixtures/config_invalid_missing_db_name.yaml
new file mode 100644
index 0000000..0e2ea39
--- /dev/null
+++ b/tests/unit/fixtures/config_invalid_missing_db_name.yaml
@@ -0,0 +1,18 @@
+config:
+    cors_origin: '*'
+    developer_emails: [e-mail]
+    discourse_image: discourse-k8s:1.0.7f
+    enable_cors: true
+    external_hostname: discourse.local
+    image_pass: ''
+    image_user: ''
+    redis_host: 10.9.89.197
+    smtp_address: 167.89.123.58
+    smtp_authentication: login
+    smtp_domain: example.com
+    smtp_openssl_verify_mode: none
+    smtp_password: OBV10USLYF4K3
+    smtp_port: 587
+    smtp_username: apikey
+missing_fields: 
+    - 'db_name'
diff --git a/tests/unit/fixtures/config_valid_complete.yaml b/tests/unit/fixtures/config_valid_complete.yaml
new file mode 100644
index 0000000..28e7367
--- /dev/null
+++ b/tests/unit/fixtures/config_valid_complete.yaml
@@ -0,0 +1,38 @@
+config: 
+    cors_origin: '*'
+    db_host: 10.9.89.237
+    db_name: discourse
+    db_password: a_real_password
+    db_user: discourse_m
+    developer_emails: [e-mail]
+    discourse_image: discourse-k8s:1.0.7f
+    enable_cors: true
+    external_hostname: discourse.local
+    image_pass: ''
+    image_user: ''
+    redis_host: 10.9.89.197
+    smtp_address: 167.89.123.58
+    smtp_authentication: login
+    smtp_domain: example.com
+    smtp_openssl_verify_mode: none
+    smtp_password: OBV10USLYF4K3
+    smtp_port: 587
+    smtp_username: apikey
+    tls_secret_name: discourse_local
+pod_config:
+    DISCOURSE_CORS_ORIGIN: '*'
+    DISCOURSE_DEVELOPER_EMAILS: [e-mail]
+    DISCOURSE_ENABLE_CORS: true
+    DISCOURSE_HOSTNAME: discourse.local
+    DISCOURSE_POSTGRES_HOST: 10.9.89.237
+    DISCOURSE_POSTGRES_NAME: discourse
+    DISCOURSE_POSTGRES_PASSWORD: a_real_password
+    DISCOURSE_POSTGRES_USERNAME: discourse_m
+    DISCOURSE_REDIS_HOST: 10.9.89.197
+    DISCOURSE_SMTP_ADDRESS: 167.89.123.58
+    DISCOURSE_SMTP_AUTHENTICATION: login
+    DISCOURSE_SMTP_DOMAIN: example.com
+    DISCOURSE_SMTP_OPENSSL_VERIFY_MODE: none
+    DISCOURSE_SMTP_PASSWORD: OBV10USLYF4K3
+    DISCOURSE_SMTP_PORT: 587
+    DISCOURSE_SMTP_USER_NAME: apikey
diff --git a/tests/unit/fixtures/config_valid_with_tls.yaml b/tests/unit/fixtures/config_valid_with_tls.yaml
new file mode 100644
index 0000000..fa19ce1
--- /dev/null
+++ b/tests/unit/fixtures/config_valid_with_tls.yaml
@@ -0,0 +1,38 @@
+config: 
+    cors_origin: '*'
+    db_host: 10.9.89.237
+    db_name: discourse
+    db_password: a_real_password
+    db_user: discourse_m
+    developer_emails: [e-mail]
+    discourse_image: discourse-k8s:1.0.7f
+    enable_cors: true
+    external_hostname: discourse.local
+    image_pass: 'discourse123'
+    image_user: 'discourse_role'
+    redis_host: 10.9.89.197
+    smtp_address: 167.89.123.58
+    smtp_authentication: login
+    smtp_domain: example.com
+    smtp_openssl_verify_mode: none
+    smtp_password: OBV10USLYF4K3
+    smtp_port: 587
+    smtp_username: apikey
+    tls_secret_name: discourse-local
+pod_config:
+    DISCOURSE_CORS_ORIGIN: '*'
+    DISCOURSE_DEVELOPER_EMAILS: [e-mail]
+    DISCOURSE_ENABLE_CORS: true
+    DISCOURSE_HOSTNAME: discourse.local
+    DISCOURSE_POSTGRES_HOST: 10.9.89.237
+    DISCOURSE_POSTGRES_NAME: discourse
+    DISCOURSE_POSTGRES_PASSWORD: a_real_password
+    DISCOURSE_POSTGRES_USERNAME: discourse_m
+    DISCOURSE_REDIS_HOST: 10.9.89.197
+    DISCOURSE_SMTP_ADDRESS: 167.89.123.58
+    DISCOURSE_SMTP_AUTHENTICATION: login
+    DISCOURSE_SMTP_DOMAIN: example.com
+    DISCOURSE_SMTP_OPENSSL_VERIFY_MODE: none
+    DISCOURSE_SMTP_PASSWORD: OBV10USLYF4K3
+    DISCOURSE_SMTP_PORT: 587
+    DISCOURSE_SMTP_USER_NAME: apikey
diff --git a/tests/unit/fixtures/config_valid_without_tls.yaml b/tests/unit/fixtures/config_valid_without_tls.yaml
new file mode 100644
index 0000000..8c440b8
--- /dev/null
+++ b/tests/unit/fixtures/config_valid_without_tls.yaml
@@ -0,0 +1,37 @@
+config: 
+    cors_origin: '*'
+    db_host: 10.9.89.237
+    db_name: discourse
+    db_password: a_real_password
+    db_user: discourse_m
+    developer_emails: [e-mail]
+    discourse_image: discourse-k8s:1.0.8
+    enable_cors: true
+    external_hostname: discourse.example.com
+    image_pass: ''
+    image_user: ''
+    redis_host: 10.25.242.12
+    smtp_address: smtp.internal
+    smtp_authentication: login
+    smtp_domain: example.com
+    smtp_openssl_verify_mode: none
+    smtp_password:
+    smtp_port: 587
+    smtp_username: apikey
+pod_config:
+    DISCOURSE_CORS_ORIGIN: '*'
+    DISCOURSE_DEVELOPER_EMAILS: [e-mail]
+    DISCOURSE_ENABLE_CORS: true
+    DISCOURSE_HOSTNAME: discourse.example.com
+    DISCOURSE_POSTGRES_HOST: 10.9.89.237
+    DISCOURSE_POSTGRES_NAME: discourse
+    DISCOURSE_POSTGRES_PASSWORD: a_real_password
+    DISCOURSE_POSTGRES_USERNAME: discourse_m
+    DISCOURSE_REDIS_HOST: 10.25.242.12
+    DISCOURSE_SMTP_ADDRESS: smtp.internal
+    DISCOURSE_SMTP_AUTHENTICATION: login
+    DISCOURSE_SMTP_DOMAIN: example.com
+    DISCOURSE_SMTP_OPENSSL_VERIFY_MODE: none
+    DISCOURSE_SMTP_PASSWORD: null
+    DISCOURSE_SMTP_PORT: 587
+    DISCOURSE_SMTP_USER_NAME: apikey
diff --git a/tests/unit/requirements.txt b/tests/unit/requirements.txt
new file mode 100644
index 0000000..65431fc
--- /dev/null
+++ b/tests/unit/requirements.txt
@@ -0,0 +1,4 @@
+mock
+pytest
+pytest-cov
+pyyaml
diff --git a/tests/unit/test_charm.py b/tests/unit/test_charm.py
new file mode 100644
index 0000000..8dc65d8
--- /dev/null
+++ b/tests/unit/test_charm.py
@@ -0,0 +1,135 @@
+#!/usr/bin/env python3
+
+# Copyright 2020 Canonical Ltd.
+# See LICENSE file for licensing details.
+
+import copy
+import glob
+import mock
+import os
+import unittest
+import yaml
+
+from types import SimpleNamespace
+
+from charm import (
+    check_for_missing_config_fields,
+    create_discourse_pod_config,
+    get_pod_spec,
+    DiscourseCharm,
+)
+
+from ops import testing
+
+
+def load_configs(directory):
+    """Load configs for use by tests.
+
+    Valid and invalid configs are present in the fixtures directory. The files
+    contain the juju config, along with the spec that that config should
+    produce in the case of valid configs. In the case of invalid configs, they
+    contain the juju config and the error that should be triggered by the
+    config. These scenarios are tested below. Additional config variations can
+    be created by creating an appropriately named config file in the fixtures
+    directory. Valid configs should be named: config_valid_###.yaml and invalid
+    configs should be named: config_invalid_###.yaml."""
+    configs = {}
+    for filename in glob.glob(os.path.join(directory, 'config*.yaml')):
+        with open(filename) as file:
+            name, _ = os.path.splitext(os.path.basename(filename))
+            configs[name] = yaml.full_load(file)
+    return configs
+
+
+class TestDiscourseK8sCharmHooksDisabled(unittest.TestCase):
+    def setUp(self):
+        self.harness = testing.Harness(DiscourseCharm)
+        self.harness.disable_hooks()
+        self.harness.set_leader(True)
+        self.harness.begin()
+        self.configs = load_configs(os.path.join(os.path.dirname(__file__), 'fixtures'))
+
+    def test_valid_configs_are_ok(self):
+        """Test that a valid config is considered valid."""
+        for config_key in self.configs:
+            if config_key.startswith('config_valid_'):
+                config_valid = self.harness.charm.check_config_is_valid(self.configs[config_key]['config'])
+                pod_config = create_discourse_pod_config(self.configs[config_key]['config'])
+                self.assertEqual(config_valid, True, 'Valid config is not recognized as valid')
+                self.assertEqual(
+                    pod_config,
+                    self.configs[config_key]['pod_config'],
+                    'Valid config {} is does not produce expected config options for pod.'.format(config_key),
+                )
+
+    def test_invalid_configs_are_recognized(self):
+        """Test that bad configs are identified by the charm."""
+        for config_key in self.configs:
+            if config_key.startswith('config_invalid_'):
+                config_valid = self.harness.charm.check_config_is_valid(self.configs[config_key]['config'])
+                missing_fields = check_for_missing_config_fields(self.configs[config_key]['config'])
+                self.assertEqual(config_valid, False, 'Invalid config is not recognized as invalid')
+                self.assertEqual(
+                    missing_fields,
+                    self.configs[config_key]['missing_fields'],
+                    'Invalid config {} does not fail as expected.'.format(config_key),
+                )
+
+    def test_charm_config_process(self):
+        """Test that the entire config process for the charm works."""
+        test_config = copy.deepcopy(self.configs['config_valid_complete']['config'])
+        test_config['db_user'] = 'discourse_m'
+        test_config['db_password'] = 'a_real_password'
+        test_config['db_host'] = '10.9.89.237'
+        db_event = SimpleNamespace()
+        db_event.master = SimpleNamespace()
+        db_event.master.user = 'discourse_m'
+        db_event.master.password = 'a_real_password'
+        db_event.master.host = '10.9.89.237'
+        expected_spec = (get_pod_spec(self.harness.charm.framework.model.app.name, test_config), None)
+        self.harness.update_config(self.configs['config_valid_complete']['config'])
+        self.harness.charm.on_database_relation_joined(db_event)
+        self.harness.charm.on_database_changed(db_event)
+        configured_spec = self.harness.get_pod_spec()
+        self.assertEqual(configured_spec, expected_spec, 'Configured spec does not match expected pod spec.')
+
+    def test_charm_config_process_not_leader(self):
+        """Test that the config process on a non-leader does not trigger a pod_spec change."""
+        non_leader_harness = testing.Harness(DiscourseCharm)
+        non_leader_harness.disable_hooks()
+        non_leader_harness.set_leader(False)
+        non_leader_harness.begin()
+
+        action_event = mock.Mock()
+        non_leader_harness.update_config(self.configs['config_valid_complete']['config'])
+        non_leader_harness.charm.configure_pod(action_event)
+        result = non_leader_harness.get_pod_spec()
+        self.assertEqual(result, None, 'Non-leader does not set pod spec.')
+
+    def test_lost_db_relation(self):
+        """Test that losing our DB relation triggers a drop of pod config."""
+        self.harness.update_config(self.configs['config_valid_complete']['config'])
+        db_event = SimpleNamespace()
+        db_event.master = None
+        self.harness.charm.on_database_changed(db_event)
+        configured_spec = self.harness.get_pod_spec()
+        self.assertEqual(configured_spec, None, 'Lost DB relation does not result in empty spec as expected')
+
+    def test_on_database_relation_joined(self):
+        """Test joining the DB relation."""
+        # First test with a non-leader, confirm the database property isn't set.
+        non_leader_harness = testing.Harness(DiscourseCharm)
+        non_leader_harness.disable_hooks()
+        non_leader_harness.set_leader(False)
+        non_leader_harness.begin()
+
+        action_event = mock.Mock()
+        action_event.database = None
+        non_leader_harness.update_config(self.configs['config_valid_complete']['config'])
+        non_leader_harness.charm.on_database_relation_joined(action_event)
+        self.assertEqual(action_event.database, None)
+
+        # Now test with a leader, the database property is set.
+        self.harness.update_config(self.configs['config_valid_complete']['config'])
+        self.harness.charm.on_database_relation_joined(action_event)
+        self.assertEqual(action_event.database, "discourse")