perf: don't call GetUserByID unnecessarily for Agents metrics loops (#19395)

At the moment, the loop which retrieves and updates the values of the
agents metrics excessively calls `GetUserByID` (a DB query). First it
retrieves a list of all workspaces, filtering out inactive agents (not
entirely clear to me whether this is non-running workspaces, or just
dead agents), and then iterates over those workspaces to get the rest of
the relevant data for the metrics. The next call is `GetUserByID` for
`workspace.OwnerID`. This is unnecessary because the `workspaces_visible` view we pull workspaces from has already been joined with the users table to get the username/name/etc.

This should at least partially resolve
https://github.com/coder/internal/issues/726 
---------

Signed-off-by: Callum Styan <callumstyan@gmail.com>

coderd/agentapi/stats_test.go

@@ -41,11 +41,12 @@ func TestUpdateStates(t *testing.T) {
 			Name: "tpl",
 		}
 		workspace = database.Workspace{
-			ID:           uuid.New(),
+			ID:            uuid.New(),
-			OwnerID:      user.ID,
+			OwnerID:       user.ID,
-			TemplateID:   template.ID,
+			OwnerUsername: user.Username,
-			Name:         "xyz",
+			TemplateID:    template.ID,
-			TemplateName: template.Name,
+			Name:          "xyz",
+			TemplateName:  template.Name,
 		}
 		agent = database.WorkspaceAgent{
 			ID:   uuid.New(),
@@ -138,9 +139,6 @@ func TestUpdateStates(t *testing.T) {
 		// Workspace gets fetched.
 		dbM.EXPECT().GetWorkspaceByAgentID(gomock.Any(), agent.ID).Return(workspace, nil)
 
-		// User gets fetched to hit the UpdateAgentMetricsFn.
-		dbM.EXPECT().GetUserByID(gomock.Any(), user.ID).Return(user, nil)
-
 		// We expect an activity bump because ConnectionCount > 0.
 		dbM.EXPECT().ActivityBumpWorkspace(gomock.Any(), database.ActivityBumpWorkspaceParams{
 			WorkspaceID:   workspace.ID,
@@ -380,9 +378,6 @@ func TestUpdateStates(t *testing.T) {
 			LastUsedAt: now.UTC(),
 		}).Return(nil)
 
-		// User gets fetched to hit the UpdateAgentMetricsFn.
-		dbM.EXPECT().GetUserByID(gomock.Any(), user.ID).Return(user, nil)
-
 		resp, err := api.UpdateStats(context.Background(), req)
 		require.NoError(t, err)
 		require.Equal(t, &agentproto.UpdateStatsResponse{
@@ -498,9 +493,6 @@ func TestUpdateStates(t *testing.T) {
 			LastUsedAt: now,
 		}).Return(nil)
 
-		// User gets fetched to hit the UpdateAgentMetricsFn.
-		dbM.EXPECT().GetUserByID(gomock.Any(), user.ID).Return(user, nil)
-
 		// Ensure that pubsub notifications are sent.
 		notifyDescription := make(chan struct{})
 		ps.SubscribeWithErr(wspubsub.WorkspaceEventChannel(workspace.OwnerID),

coderd/prometheusmetrics/prometheusmetrics.go

@@ -328,29 +328,24 @@ func Agents(ctx context.Context, logger slog.Logger, registerer prometheus.Regis
 					templateVersionName = "unknown"
 				}
 
-				user, err := db.GetUserByID(ctx, workspace.OwnerID)
+				// username :=
-				if err != nil {
-					logger.Error(ctx, "can't get user from the database", slog.F("user_id", workspace.OwnerID), slog.Error(err))
-					agentsGauge.WithLabelValues(VectorOperationAdd, 0, user.Username, workspace.Name, templateName, templateVersionName)
-					continue
-				}
 
 				agents, err := db.GetWorkspaceAgentsInLatestBuildByWorkspaceID(ctx, workspace.ID)
 				if err != nil {
 					logger.Error(ctx, "can't get workspace agents", slog.F("workspace_id", workspace.ID), slog.Error(err))
-					agentsGauge.WithLabelValues(VectorOperationAdd, 0, user.Username, workspace.Name, templateName, templateVersionName)
+					agentsGauge.WithLabelValues(VectorOperationAdd, 0, workspace.OwnerUsername, workspace.Name, templateName, templateVersionName)
 					continue
 				}
 
 				if len(agents) == 0 {
 					logger.Debug(ctx, "workspace agents are unavailable", slog.F("workspace_id", workspace.ID))
-					agentsGauge.WithLabelValues(VectorOperationAdd, 0, user.Username, workspace.Name, templateName, templateVersionName)
+					agentsGauge.WithLabelValues(VectorOperationAdd, 0, workspace.OwnerUsername, workspace.Name, templateName, templateVersionName)
 					continue
 				}
 
 				for _, agent := range agents {
 					// Collect information about agents
-					agentsGauge.WithLabelValues(VectorOperationAdd, 1, user.Username, workspace.Name, templateName, templateVersionName)
+					agentsGauge.WithLabelValues(VectorOperationAdd, 1, workspace.OwnerUsername, workspace.Name, templateName, templateVersionName)
 
 					connectionStatus := agent.Status(agentInactiveDisconnectTimeout)
 					node := (*coordinator.Load()).Node(agent.ID)
@@ -360,7 +355,7 @@ func Agents(ctx context.Context, logger slog.Logger, registerer prometheus.Regis
 						tailnetNode = node.ID.String()
 					}
 
-					agentsConnectionsGauge.WithLabelValues(VectorOperationSet, 1, agent.Name, user.Username, workspace.Name, string(connectionStatus.Status), string(agent.LifecycleState), tailnetNode)
+					agentsConnectionsGauge.WithLabelValues(VectorOperationSet, 1, agent.Name, workspace.OwnerUsername, workspace.Name, string(connectionStatus.Status), string(agent.LifecycleState), tailnetNode)
 
 					if node == nil {
 						logger.Debug(ctx, "can't read in-memory node for agent", slog.F("agent_id", agent.ID))
@@ -385,7 +380,7 @@ func Agents(ctx context.Context, logger slog.Logger, registerer prometheus.Regis
 								}
 							}
 
-							agentsConnectionLatenciesGauge.WithLabelValues(VectorOperationSet, latency, agent.Name, user.Username, workspace.Name, region.RegionName, fmt.Sprintf("%v", node.PreferredDERP == regionID))
+							agentsConnectionLatenciesGauge.WithLabelValues(VectorOperationSet, latency, agent.Name, workspace.OwnerUsername, workspace.Name, region.RegionName, fmt.Sprintf("%v", node.PreferredDERP == regionID))
 						}
 					}
 
@@ -397,7 +392,7 @@ func Agents(ctx context.Context, logger slog.Logger, registerer prometheus.Regis
 					}
 
 					for _, app := range apps {
-						agentsAppsGauge.WithLabelValues(VectorOperationAdd, 1, agent.Name, user.Username, workspace.Name, app.DisplayName, string(app.Health))
+						agentsAppsGauge.WithLabelValues(VectorOperationAdd, 1, agent.Name, workspace.OwnerUsername, workspace.Name, app.DisplayName, string(app.Health))
 					}
 				}
 			}

coderd/workspacestats/reporter.go

@@ -126,13 +126,8 @@ func (r *Reporter) ReportAgentStats(ctx context.Context, now time.Time, workspac
 
 	// update prometheus metrics
 	if r.opts.UpdateAgentMetricsFn != nil {
-		user, err := r.opts.Database.GetUserByID(ctx, workspace.OwnerID)
-		if err != nil {
-			return xerrors.Errorf("get user: %w", err)
-		}
-
 		r.opts.UpdateAgentMetricsFn(ctx, prometheusmetrics.AgentMetricLabels{
-			Username:      user.Username,
+			Username:      workspace.OwnerUsername,
 			WorkspaceName: workspace.Name,
 			AgentName:     workspaceAgent.Name,
 			TemplateName:  templateName,