fix(coderd): workspaceapps: update last_used_at when workspace app reports stats (#11603)

- Adds a new query BatchUpdateLastUsedAt
- Adds calls to BatchUpdateLastUsedAt in app stats handler upon flush
- Passes a stats flush channel to apptest setup scaffolding and updates unit tests to assert modifications to LastUsedAt.

coderd/database/dbauthz/dbauthz.go

@@ -695,6 +695,15 @@ func (q *querier) ArchiveUnusedTemplateVersions(ctx context.Context, arg databas
 	return q.db.ArchiveUnusedTemplateVersions(ctx, arg)
 }
 
+func (q *querier) BatchUpdateWorkspaceLastUsedAt(ctx context.Context, arg database.BatchUpdateWorkspaceLastUsedAtParams) error {
+	// Could be any workspace and checking auth to each workspace is overkill for the purpose
+	// of this function.
+	if err := q.authorizeContext(ctx, rbac.ActionUpdate, rbac.ResourceWorkspace.All()); err != nil {
+		return err
+	}
+	return q.db.BatchUpdateWorkspaceLastUsedAt(ctx, arg)
+}
+
 func (q *querier) CleanTailnetCoordinators(ctx context.Context) error {
 	if err := q.authorizeContext(ctx, rbac.ActionDelete, rbac.ResourceTailnetCoordinator); err != nil {
 		return err

coderd/database/dbauthz/dbauthz_test.go

@@ -1549,6 +1549,13 @@ func (s *MethodTestSuite) TestWorkspace() {
 			ID: ws.ID,
 		}).Asserts(ws, rbac.ActionUpdate).Returns()
 	}))
+	s.Run("BatchUpdateWorkspaceLastUsedAt", s.Subtest(func(db database.Store, check *expects) {
+		ws1 := dbgen.Workspace(s.T(), db, database.Workspace{})
+		ws2 := dbgen.Workspace(s.T(), db, database.Workspace{})
+		check.Args(database.BatchUpdateWorkspaceLastUsedAtParams{
+			IDs: []uuid.UUID{ws1.ID, ws2.ID},
+		}).Asserts(rbac.ResourceWorkspace.All(), rbac.ActionUpdate).Returns()
+	}))
 	s.Run("UpdateWorkspaceTTL", s.Subtest(func(db database.Store, check *expects) {
 		ws := dbgen.Workspace(s.T(), db, database.Workspace{})
 		check.Args(database.UpdateWorkspaceTTLParams{

coderd/database/dbmem/dbmem.go

@@ -963,6 +963,31 @@ func (q *FakeQuerier) ArchiveUnusedTemplateVersions(_ context.Context, arg datab
 	return archived, nil
 }
 
+func (q *FakeQuerier) BatchUpdateWorkspaceLastUsedAt(_ context.Context, arg database.BatchUpdateWorkspaceLastUsedAtParams) error {
+	err := validateDatabaseType(arg)
+	if err != nil {
+		return err
+	}
+
+	q.mutex.Lock()
+	defer q.mutex.Unlock()
+
+	// temporary map to avoid O(q.workspaces*arg.workspaceIds)
+	m := make(map[uuid.UUID]struct{})
+	for _, id := range arg.IDs {
+		m[id] = struct{}{}
+	}
+	n := 0
+	for i := 0; i < len(q.workspaces); i++ {
+		if _, found := m[q.workspaces[i].ID]; !found {
+			continue
+		}
+		q.workspaces[i].LastUsedAt = arg.LastUsedAt
+		n++
+	}
+	return nil
+}
+
 func (*FakeQuerier) CleanTailnetCoordinators(_ context.Context) error {
 	return ErrUnimplemented
 }

coderd/database/dbmetrics/dbmetrics.go

@@ -114,6 +114,13 @@ func (m metricsStore) ArchiveUnusedTemplateVersions(ctx context.Context, arg dat
 	return r0, r1
 }
 
+func (m metricsStore) BatchUpdateWorkspaceLastUsedAt(ctx context.Context, arg database.BatchUpdateWorkspaceLastUsedAtParams) error {
+	start := time.Now()
+	r0 := m.s.BatchUpdateWorkspaceLastUsedAt(ctx, arg)
+	m.queryLatencies.WithLabelValues("BatchUpdateWorkspaceLastUsedAt").Observe(time.Since(start).Seconds())
+	return r0
+}
+
 func (m metricsStore) CleanTailnetCoordinators(ctx context.Context) error {
 	start := time.Now()
 	err := m.s.CleanTailnetCoordinators(ctx)

coderd/database/dbmock/dbmock.go

@@ -117,6 +117,20 @@ func (mr *MockStoreMockRecorder) ArchiveUnusedTemplateVersions(arg0, arg1 any) *
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ArchiveUnusedTemplateVersions", reflect.TypeOf((*MockStore)(nil).ArchiveUnusedTemplateVersions), arg0, arg1)
 }
 
+// BatchUpdateWorkspaceLastUsedAt mocks base method.
+func (m *MockStore) BatchUpdateWorkspaceLastUsedAt(arg0 context.Context, arg1 database.BatchUpdateWorkspaceLastUsedAtParams) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "BatchUpdateWorkspaceLastUsedAt", arg0, arg1)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// BatchUpdateWorkspaceLastUsedAt indicates an expected call of BatchUpdateWorkspaceLastUsedAt.
+func (mr *MockStoreMockRecorder) BatchUpdateWorkspaceLastUsedAt(arg0, arg1 any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "BatchUpdateWorkspaceLastUsedAt", reflect.TypeOf((*MockStore)(nil).BatchUpdateWorkspaceLastUsedAt), arg0, arg1)
+}
+
 // CleanTailnetCoordinators mocks base method.
 func (m *MockStore) CleanTailnetCoordinators(arg0 context.Context) error {
 	m.ctrl.T.Helper()

coderd/database/querier.go

@@ -42,6 +42,7 @@ type sqlcQuerier interface {
 	// Only unused template versions will be archived, which are any versions not
 	// referenced by the latest build of a workspace.
 	ArchiveUnusedTemplateVersions(ctx context.Context, arg ArchiveUnusedTemplateVersionsParams) ([]uuid.UUID, error)
+	BatchUpdateWorkspaceLastUsedAt(ctx context.Context, arg BatchUpdateWorkspaceLastUsedAtParams) error
 	CleanTailnetCoordinators(ctx context.Context) error
 	CleanTailnetLostPeers(ctx context.Context) error
 	CleanTailnetTunnels(ctx context.Context) error

coderd/database/queries.sql.go

@@ -10813,6 +10813,25 @@ func (q *sqlQuerier) InsertWorkspaceResourceMetadata(ctx context.Context, arg In
 	return items, nil
 }
 
+const batchUpdateWorkspaceLastUsedAt = `-- name: BatchUpdateWorkspaceLastUsedAt :exec
+UPDATE
+	workspaces
+SET
+	last_used_at = $1
+WHERE
+	id = ANY($2 :: uuid[])
+`
+
+type BatchUpdateWorkspaceLastUsedAtParams struct {
+	LastUsedAt time.Time   `db:"last_used_at" json:"last_used_at"`
+	IDs        []uuid.UUID `db:"ids" json:"ids"`
+}
+
+func (q *sqlQuerier) BatchUpdateWorkspaceLastUsedAt(ctx context.Context, arg BatchUpdateWorkspaceLastUsedAtParams) error {
+	_, err := q.db.ExecContext(ctx, batchUpdateWorkspaceLastUsedAt, arg.LastUsedAt, pq.Array(arg.IDs))
+	return err
+}
+
 const getDeploymentWorkspaceStats = `-- name: GetDeploymentWorkspaceStats :one
 WITH workspaces_with_jobs AS (
 	SELECT

coderd/database/queries/workspaces.sql

@@ -357,6 +357,14 @@ SET
 WHERE
 	id = $1;
 
+-- name: BatchUpdateWorkspaceLastUsedAt :exec
+UPDATE
+	workspaces
+SET
+	last_used_at = @last_used_at
+WHERE
+	id = ANY(@ids :: uuid[]);
+
 -- name: GetDeploymentWorkspaceStats :one
 WITH workspaces_with_jobs AS (
 	SELECT