Merge ~pjdc/prometheus-mongodb-exporter-charm/+git/prometheus-mongodb-exporter-charm:no-needless-blocked into prometheus-mongodb-exporter-charm:master

[Paul Collins]

ensure installation happens immediately after setting mongodb_uri to juju-db://

[🤖 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)]

The maybe_block_on_mongodb_uri() handler may end up running before the is_mongodb_uri_usable() handler, causing a spurious blocked state.

Instead, I'd just do:

@when('config.default.mongodb_uri') # default is empty string
def block_on_no_uri():
    blocked('mongodb_uri must be set')

@when('config.changed.mongodb_uri')
def local_or_remote():
    l = mongodb_uri_is_juju_db()
    reactive.toggle_flag('prometheus-mongodb-exporter.monitor-juju-db', l)
    reactive.toggle_flag('prometheus-mongodb-exporter.monitor-remote-db', not l)

@when('prometheus-mongodb-exporter.monitor-juju-db')
@when_not('leadership.is_leader', 'leadership.set.mongodb_uri')
def wait_on_leader():
    waiting('Waiting for leader to provide mongodb credentials')

@when('prometheus-mongodb-exporter.monitor-juju-db')
@when('leadership.is_leader')
@when_not('leadership.set.mongodb_uri')
def create_juju_db_user():
    [ ... existing code ... ]

review: Needs Fixing

Unmerged commits

681810e... by Paul Collins on 2019-09-04

ensure installation happens immediately after setting mongodb_uri to juju-db://

Previously, install_prometheus_mongodb_exporter would bail when
the config item was "juju-db://" but the leader setting was empty,
because create_juju_db_user had not yet been invoked.

diff --git a/reactive/prometheus_mongodb_exporter.py b/reactive/prometheus_mongodb_exporter.py
index ae2d3d3..ec32635 100644
--- a/reactive/prometheus_mongodb_exporter.py
+++ b/reactive/prometheus_mongodb_exporter.py
@@ -81,6 +81,25 @@ def maybe_monitor_juju_db():
         remove_state('prometheus-mongodb-exporter.monitor-juju-db')
 
 
+@when_any('config.changed.mongodb_uri', 'leadership.changed.mongodb_uri')
+def is_mongodb_uri_usable():
+    if get_mongodb_uri():
+        set_state('prometheus-mongodb-exporter.mongodb_uri.usable')
+    else:
+        remove_state('prometheus-mongodb-exporter.mongodb_uri.usable')
+
+
+@when_not('prometheus-mongodb-exporter.mongodb_uri.usable')
+def maybe_block_on_mongodb_uri():
+    if get_mongodb_uri():
+        return
+    if mongodb_uri_is_juju_db():
+        # The config item is "juju-db://" but the leader setting is empty,
+        # which create_juju_db_user will fix shortly; let it have its chance.
+        return
+    blocked('mongodb_uri must be set')
+
+
 @when('prometheus-mongodb-exporter.monitor-juju-db')
 @when('leadership.is_leader')
 @when_not('leadership.set.mongodb_uri')
@@ -121,6 +140,7 @@ def create_juju_db_user():
     leader_set(mongodb_uri='mongodb://{}:{}@localhost:37017/admin'.format(username, password))
 
 
+@when('prometheus-mongodb-exporter.mongodb_uri.usable')
 @when_not('prometheus-mongodb-exporter.installed')
 def install_prometheus_mongodb_exporter():
     ''' Install the proxy application '''
@@ -130,10 +150,6 @@ def install_prometheus_mongodb_exporter():
 
     snap.install('prometheus-mongodb-exporter')
 
-    if not uri:
-        blocked('mongodb_uri must be set')
-        return
-
     # Create a systemd unit file, and open the port.
     port = hookenv.config()['port']
     if not sensible_port(port):
@@ -168,6 +184,7 @@ def update_opened_port():
     hookenv.open_port(new_port)
 
 
+@when('prometheus-mongodb-exporter.mongodb_uri.usable')
 @when('prometheus-mongodb-exporter.installed')
 @when_any('config.changed', 'leadership.changed')
 def update_daemon_args():