Merge ~pjdc/charm-k8s-mattermost/+git/charm-k8s-mattermost:psql-relation into charm-k8s-mattermost:master

[Paul Collins]

add db relation and wire it up

[Paul Collins (pjdc)]

Depends on fixes in https://code.launchpad.net/~pjdc/interface-pgsql/+git/operator/+merge/384313

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[Stuart Bishop (stub)]

A minor tweak to the docs (postgresql:db), and update the pgsql interface with code landed yesterday. Juju 2.8 is now mostly enforcing the limit: setting in the relation definition, so you can remove some ugly code.

review: Approve

[Stuart Bishop (stub)]

I also note that this charm does not handle the db relation being removed, but that is fine as the app will fail the same way no matter its db creds becoming invalid or the db creds no longer existing.

[Paul Collins (pjdc)]

Reply re offer/consume and egress-subnets.

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision 89623f2407b385a6b46e68b05774d035149bbb9b

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b25c15b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+*~
diff --git a/.gitmodules b/.gitmodules
index d3eb83f..49f5dd7 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -4,3 +4,6 @@
 [submodule "mod/resource-oci-image"]
 	path = mod/resource-oci-image
 	url = https://github.com/johnsca/resource-oci-image
+[submodule "mod/interface-pgsql"]
+	path = mod/interface-pgsql
+	url = lp:~stub/interface-pgsql/+git/operator
diff --git a/README.md b/README.md
index 2024a9c..8a82fca 100644
--- a/README.md
+++ b/README.md
@@ -5,28 +5,20 @@ configurable to use a postgresql backend.
 
 ## Overview
 
-This is a k8s charm and can only be deployed to to a Juju k8s cloud,
-attached to a controller using `juju add-k8s`.
+This is a k8s workload charm and can only be deployed to to a Juju k8s
+cloud, attached to a controller using `juju add-k8s`.
 
-Configuration for the Mattermost image is in standard Juju config. In
-particular:
+On a fresh deployment, you need to set Mattermost in Open Server mode,
+which will let you create an admin account.  Once this is done, you
+can restrict access with:
 
-* `pg_db_host`, `pg_db_port`, `pg_user`, `pg_password`: this charm should be
-  able in the future, to relate to postgresql, but as of now these parameters
-  allow setting up the connection.
-
-On a fresh deployment, you need to set Mattermost in Open Server mode, which will let you create an admin account.
-Once this is done, you can restrict access with:
-
-```
-juju config mattermost open_server=false
-```
+    juju config mattermost open_server=false
 
 ## Details
 
 See config option descriptions in config.yaml.
 
-## Quickstart
+## Getting Started
 
 Notes for deploying a test setup locally using microk8s:
 
@@ -49,6 +41,30 @@ Notes for deploying a test setup locally using microk8s:
     juju bootstrap myk8s
     juju add-model mattermost-test
     juju deploy ./charm-k8s-mattermost --resource mattermost_image=localhost:32000/mattermost:latest mattermost
-    juju config mattermost pg_db_host=10.1.1.1 pg_password=secret
     juju wait
     juju status
+
+The charm will not function without a database, so you will need to
+deploy `cs:postgresql` somewhere.
+
+If postgresql is deployed in the same model you plan to use for
+mattermost, simply use `juju relate mattermost postgresql:db`.  (This
+deployment style is recommended for testing purposes only.)
+
+Cross-model relations are also supported.  Create a suitable model on
+a different cloud, for example, LXD or OpenStack.
+
+    juju switch database
+    juju deploy cs:postgresql
+    juju offer postgresql:db
+
+In most k8s deployments, traffic to external services from worker pods
+will be SNATed by some part of the infrastructure.  You will need to
+know what the source addresses or address range is for the next step.
+
+    juju switch mattermost-test
+    juju find-offers  # note down offer URL; example used below:
+    juju relate mattermost admin/database.postgresql --via 10.9.8.0/24
+
+(In the case of postgresql, `--via` is needed so that the charm can
+configure `pga_hba.conf` to let the k8s pods connect to the database.)
diff --git a/config.yaml b/config.yaml
index dd116e8..603ba30 100644
--- a/config.yaml
+++ b/config.yaml
@@ -7,20 +7,3 @@ options:
         type: boolean
         description: Allows users to sign up from the root page without an invite
         default: false
-    pg_db_host:
-        type: string
-        description: The hostname or IP of the postgresql backend.
-        default: ''
-    pg_db_port:
-        type: int
-        description: The port number for the postgresql backend.
-        default: 5432
-    pg_user:
-        type: string
-        description: The postgresql user.
-        default: 'mattermost'
-    pg_password:
-        type: string
-        description: The postgresql password.
-        default: ''
-        
diff --git a/lib/interface/pgsql b/lib/interface/pgsql
new file mode 120000
index 0000000..fac7ffe
--- /dev/null
+++ b/lib/interface/pgsql
@@ -0,0 +1 @@
+../../mod/interface-pgsql/pgsql
\ No newline at end of file
diff --git a/metadata.yaml b/metadata.yaml
index 7f2c63e..e03364e 100644
--- a/metadata.yaml
+++ b/metadata.yaml
@@ -1,14 +1,19 @@
 name: mattermost
 summary: Mattermost charm
-maitainers:
+maintainers:
   - launchpad.net/~canonical-is-sre
 description: |
   A charm which deploys Mattermost on kubernetes.
   Mattermost is a flexible, open source messaging platform that enables
   secure team collaboration.
   https://mattermost.com
+min-juju-version: 2.8.0  # charm storage in state
 series:
   - kubernetes
+requires:
+  db:
+    interface: pgsql
+    limit: 1
 resources:
   mattermost_image:
     type: oci-image
diff --git a/mod/interface-pgsql b/mod/interface-pgsql
new file mode 160000
index 0000000..8daab41
--- /dev/null
+++ b/mod/interface-pgsql
@@ -0,0 +1 @@
+Subproject commit 8daab41e46aa144ac93c766a723238561e6c5e73
diff --git a/src/charm.py b/src/charm.py
index 864754f..0fcc304 100755
--- a/src/charm.py
+++ b/src/charm.py
@@ -1,28 +1,51 @@
 #!/usr/bin/env python3
 
 import sys
-sys.path.append('lib')
-from ops.charm import CharmBase  # NoQA: E402
-from ops.framework import StoredState  # NoQA: E402
-from ops.main import main  # NoQA: E402
-from ops.model import (  # NoQA: E402
+sys.path.append('lib')  # noqa: E402
+
+from ops.charm import (
+    CharmBase,
+    CharmEvents,
+)
+from ops.framework import (
+    EventBase,
+    EventSource,
+    StoredState,
+)
+from ops.main import main
+from ops.model import (
     ActiveStatus,
     MaintenanceStatus,
     WaitingStatus,
 )
 
+from interface import pgsql
 from oci_image import OCIImageResource
 
-import logging  # NoQA: E402
+import logging
 logger = logging.getLogger()
 
 
+DATABASE_NAME = 'mattermost'
+
+
+class MattermostDBMasterAvailableEvent(EventBase):
+    pass
+
+
+class MattermostCharmEvents(CharmEvents):
+    """Custom charm events."""
+    db_master_available = EventSource(MattermostDBMasterAvailableEvent)
+
+
 class MattermostK8sCharm(CharmBase):
 
     state = StoredState()
+    on = MattermostCharmEvents()
+
+    def __init__(self, *args):
+        super().__init__(*args)
 
-    def __init__(self, framework, key):
-        super().__init__(framework, key)
         # get our mattermost_image from juju
         # ie: juju deploy . --resource mattermost_image=mattermost:latest )
         self.mattermost_image = OCIImageResource(self, 'mattermost_image')
@@ -31,7 +54,55 @@ class MattermostK8sCharm(CharmBase):
         self.framework.observe(self.on.leader_elected, self.configure_pod)
         self.framework.observe(self.on.upgrade_charm, self.configure_pod)
 
+        # database
+        self.state.set_default(db_conn_str=None, db_uri=None, db_ro_uris=[])
+        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_master_changed)
+        self.framework.observe(self.db.on.standby_changed, self._on_standby_changed)
+        self.framework.observe(self.on.db_master_available, self.configure_pod)
+
+    def _on_database_relation_joined(self, event: pgsql.DatabaseRelationJoinedEvent):
+        if self.model.unit.is_leader():
+            # Provide requirements to the PostgreSQL server.
+            event.database = DATABASE_NAME  # Request database named mydbname
+            # event.extensions = ['citext']  # Request the citext extension installed
+        elif event.database != DATABASE_NAME:
+            # Leader has not yet set requirements. Defer, incase this unit
+            # becomes leader and needs to perform that operation.
+            event.defer()
+            return
+
+    def _on_master_changed(self, event: pgsql.MasterChangedEvent):
+        if event.database != DATABASE_NAME:
+            # Leader has not yet set requirements. Wait until next
+            # event, or risk connecting to an incorrect database.
+            return
+
+        self.state.db_conn_str = None if event.master is None else event.master.conn_str
+        self.state.db_uri = None if event.master is None else event.master.uri
+
+        if event.master is None:
+            return
+
+        self.on.db_master_available.emit()
+
+    def _on_standby_changed(self, event: pgsql.StandbyChangedEvent):
+        if event.database != DATABASE_NAME:
+            # Leader has not yet set requirements. Wait until next
+            # event, or risk connecting to an incorrect database.
+            return
+
+        self.state.db_ro_uris = [c.uri for c in event.standbys]
+
+        # TODO(pjdc): Emit event when we add support for read replicas.
+
     def configure_pod(self, event):
+        if not self.state.db_uri:
+            self.model.unit.status = WaitingStatus('Waiting for database relation')
+            event.defer()
+            return
+
         if not self.framework.model.unit.is_leader():
             self.model.unit.status = WaitingStatus('Not a leader')
             return
@@ -49,17 +120,14 @@ class MattermostK8sCharm(CharmBase):
                 }],
                 'config': {
                     'MATTERMOST_HTTPD_LISTEN_PORT': int(config['mattermost_port']),
-                    'DB_HOST': config['pg_db_host'],
-                    'DB_PORT_NUMBER': int(config['pg_db_port']),
-                    'MM_USERNAME': config['pg_user'],
-                    'MM_PASSWORD': config['pg_password'],
+                    'MM_SQLSETTINGS_DATASOURCE': self.state.db_uri,
                     'MM_ENABLEOPENSERVER': config['open_server'],
                 },
             }]
         })
         self.state.is_started = True
         self.model.unit.status = ActiveStatus()
- 
+
 
 if __name__ == '__main__':
     main(MattermostK8sCharm)