Merge pull request #11846 from howbazaar/2.8-watch-models-application…

…-status

#11846

If an application status hasn't been explicitly set by a unit its status
is derived from the units themselves. This derivation code was moved into
the model cache, but the all watcher translation later itself was overlooked.

This branch uses the cached controller information to determine the application
status if it is Unset, like the status code does.

There were no tests around the all watcher code on the apiserver side,
so added some to test the conversion behaviour.

## QA steps

```sh
juju bootstrap lxd test
juju deploy ~jameinel/ubuntu-lite ubuntu
juju db # using juju-db plugin to get mongo prompt
db.statuses.find().pretty()
# check for _id: <uuid>:a#ubuntu
# "status" : "unset",
# run pylibjuju example to look at the watcher
tox -e example -- examples/allwatcher.py 
# will see a line like:
['application', 'change', {'model-uuid': '11252a44-d946-4305-8292-a650cfa4b138', 'name': 'ubuntu', 'exposed': False, 'charm-url': 'cs:~jameinel/ubuntu-lite-7', 'owner-tag': '', 'life': 'alive', 'min-units': 0, 'constraints': {}, 'subordinate': False, 'status': {'current': 'waiting', 'message': 'waiting for machine', 'since': '2020-07-21T05:42:48.050629314Z', 'version': ''}, 'workload-version': ''}]
# confirm that status isn't 'unset'
```

apiserver/watcher.go

@@ -18,6 +18,7 @@ import (
 	"github.com/juju/juju/core/migration"
 	"github.com/juju/juju/core/multiwatcher"
 	"github.com/juju/juju/core/network"
+	"github.com/juju/juju/core/status"
 	"github.com/juju/juju/state"
 )
 
@@ -53,16 +54,18 @@ func NewAllWatcher(context facade.Context) (facade.Facade, error) {
 }
 
 type watcherCommon struct {
-	id        string
-	resources facade.Resources
-	dispose   func()
+	id         string
+	resources  facade.Resources
+	dispose    func()
+	controller *cache.Controller
 }
 
 func newWatcherCommon(context facade.Context) watcherCommon {
 	return watcherCommon{
 		context.ID(),
 		context.Resources(),
 		context.Dispose,
+		context.Controller(),
 	}
 }
 
@@ -176,6 +179,20 @@ func (aw *SrvAllWatcher) translateApplication(info multiwatcher.EntityInfo) para
 		logger.Criticalf("consistency error: %s", pretty.Sprint(info))
 		return nil
 	}
+
+	// Get the application status from the cache if it is unset.
+	applicationStatus := multiwatcher.StatusInfo{Current: status.Unknown}
+	if orig.Status.Current == status.Unset {
+		if model, err := aw.controller.Model(orig.ModelUUID); err == nil {
+			cachedApp, err := model.Application(orig.Name)
+			if err == nil {
+				applicationStatus = multiwatcher.NewStatusInfo(cachedApp.Status(), nil)
+			}
+		}
+	} else {
+		applicationStatus = orig.Status
+	}
+
 	return &params.ApplicationInfo{
 		ModelUUID:       orig.ModelUUID,
 		Name:            orig.Name,
@@ -187,7 +204,7 @@ func (aw *SrvAllWatcher) translateApplication(info multiwatcher.EntityInfo) para
 		Constraints:     orig.Constraints,
 		Config:          orig.Config,
 		Subordinate:     orig.Subordinate,
-		Status:          aw.translateStatus(orig.Status),
+		Status:          aw.translateStatus(applicationStatus),
 		WorkloadVersion: orig.WorkloadVersion,
 	}
 }

apiserver/watcher_internal_test.go

@@ -0,0 +1,135 @@
+// Copyright 2020 Canonical Ltd.
+// Licensed under the AGPLv3, see LICENCE file for details.
+
+package apiserver
+
+import (
+	"time"
+
+	"github.com/juju/worker/v2/workertest"
+	gc "gopkg.in/check.v1"
+
+	"github.com/juju/juju/apiserver/params"
+	"github.com/juju/juju/core/cache"
+	"github.com/juju/juju/core/life"
+	"github.com/juju/juju/core/multiwatcher"
+	"github.com/juju/juju/core/status"
+	"github.com/juju/juju/testing"
+	jc "github.com/juju/testing/checkers"
+)
+
+type allWatcherSuite struct {
+	testing.BaseSuite
+}
+
+var _ = gc.Suite(&allWatcherSuite{})
+
+func (s *allWatcherSuite) watcher() *SrvAllWatcher {
+	// We explicitly don't have a real watcher here as the tests
+	// are for the translation of types.
+	return &SrvAllWatcher{}
+}
+
+func (s *allWatcherSuite) TestTranslateApplicationWithStatus(c *gc.C) {
+	w := s.watcher()
+	input := &multiwatcher.ApplicationInfo{
+		ModelUUID: testing.ModelTag.Id(),
+		Name:      "test-app",
+		CharmURL:  "test-app",
+		Life:      life.Alive,
+		Status: multiwatcher.StatusInfo{
+			Current: status.Active,
+		},
+	}
+	output := w.translateApplication(input)
+	c.Assert(output, jc.DeepEquals, &params.ApplicationInfo{
+		ModelUUID: input.ModelUUID,
+		Name:      input.Name,
+		CharmURL:  input.CharmURL,
+		Life:      input.Life,
+		Status: params.StatusInfo{
+			Current: status.Active,
+		},
+	})
+}
+
+func (s *allWatcherSuite) setupCache(c *gc.C) *cache.Controller {
+	changes := make(chan interface{})
+	handled := make(chan interface{})
+	notify := func(evt interface{}) {
+		c.Logf("%#v", evt)
+		select {
+		case handled <- evt:
+		case <-time.After(testing.LongWait):
+			c.Fatalf("handled notify not retrieved")
+		}
+	}
+	sendEvent := func(event interface{}) {
+		select {
+		case changes <- event:
+		case <-time.After(testing.LongWait):
+			c.Fatal("cache did not accept event")
+		}
+		select {
+		case <-handled:
+		case <-time.After(testing.LongWait):
+			c.Fatal("cache did not handle event")
+		}
+	}
+
+	controller, err := cache.NewController(cache.ControllerConfig{
+		Changes: changes,
+		Notify:  notify,
+	})
+	c.Assert(err, jc.ErrorIsNil)
+	s.AddCleanup(func(c *gc.C) { workertest.CleanKill(c, controller) })
+
+	sendEvent(cache.ModelChange{
+		ModelUUID: testing.ModelTag.Id(),
+		// Defaults for everything else.
+	})
+	sendEvent(cache.ApplicationChange{
+		ModelUUID: testing.ModelTag.Id(),
+		Name:      "test-app",
+		Status: status.StatusInfo{
+			Status: status.Unset,
+		},
+		// Defaults for everything else.
+	})
+	sendEvent(cache.UnitChange{
+		ModelUUID:   testing.ModelTag.Id(),
+		Name:        "test-app/0",
+		Application: "test-app",
+		WorkloadStatus: status.StatusInfo{
+			Status: status.Active,
+		},
+		// Defaults for everything else.
+	})
+
+	return controller
+}
+
+func (s *allWatcherSuite) TestTranslateApplicationStatusUnset(c *gc.C) {
+	controller := s.setupCache(c)
+	w := s.watcher()
+	w.controller = controller
+	input := &multiwatcher.ApplicationInfo{
+		ModelUUID: testing.ModelTag.Id(),
+		Name:      "test-app",
+		CharmURL:  "test-app",
+		Life:      life.Alive,
+		Status: multiwatcher.StatusInfo{
+			Current: status.Unset,
+		},
+	}
+	output := w.translateApplication(input)
+	c.Assert(output, jc.DeepEquals, &params.ApplicationInfo{
+		ModelUUID: input.ModelUUID,
+		Name:      input.Name,
+		CharmURL:  input.CharmURL,
+		Life:      input.Life,
+		Status: params.StatusInfo{
+			Current: status.Active,
+		},
+	})
+}