fix: handle new agent stat format correctly (#14576)

---------

Co-authored-by: Ethan Dickson <ethan@coder.com>

coderd/metricscache/metricscache.go

@@ -34,6 +34,10 @@ type Cache struct {
 
 	done   chan struct{}
 	cancel func()
+
+	// usage is a experiment flag to enable new workspace usage tracking behavior and will be
+	// removed when the experiment is complete.
+	usage bool
 }
 
 type Intervals struct {
@@ -41,7 +45,7 @@ type Intervals struct {
 	DeploymentStats    time.Duration
 }
 
-func New(db database.Store, log slog.Logger, intervals Intervals) *Cache {
+func New(db database.Store, log slog.Logger, intervals Intervals, usage bool) *Cache {
 	if intervals.TemplateBuildTimes <= 0 {
 		intervals.TemplateBuildTimes = time.Hour
 	}
@@ -56,6 +60,7 @@ func New(db database.Store, log slog.Logger, intervals Intervals) *Cache {
 		log:       log,
 		done:      make(chan struct{}),
 		cancel:    cancel,
+		usage:     usage,
 	}
 	go func() {
 		var wg sync.WaitGroup
@@ -125,11 +130,25 @@ func (c *Cache) refreshTemplateBuildTimes(ctx context.Context) error {
 }
 
 func (c *Cache) refreshDeploymentStats(ctx context.Context) error {
-	from := dbtime.Now().Add(-15 * time.Minute)
-	agentStats, err := c.database.GetDeploymentWorkspaceAgentStats(ctx, from)
-	if err != nil {
-		return err
+	var (
+		from       = dbtime.Now().Add(-15 * time.Minute)
+		agentStats database.GetDeploymentWorkspaceAgentStatsRow
+		err        error
+	)
+
+	if c.usage {
+		agentUsageStats, err := c.database.GetDeploymentWorkspaceAgentUsageStats(ctx, from)
+		if err != nil {
+			return err
+		}
+		agentStats = database.GetDeploymentWorkspaceAgentStatsRow(agentUsageStats)
+	} else {
+		agentStats, err = c.database.GetDeploymentWorkspaceAgentStats(ctx, from)
+		if err != nil {
+			return err
+		}
 	}
+
 	workspaceStats, err := c.database.GetDeploymentWorkspaceStats(ctx)
 	if err != nil {
 		return err