fix: agent stats websocket blocking until next interval

coadler · coadler · commit 0565611b2f94 · 2022-10-17T18:31:29.000-05:00
For `httpapi.Heartbeat` to work properly, a call to `wsjson.Read` must
always be in flight, otherwise pings can't be exchanged. This caused
the ping loop to hang until the next stat interval. Since the loop was
blocking until the next interval it would also never exit until it
fired.
diff --git a/coderd/workspaceagents.go b/coderd/workspaceagents.go
@@ -757,18 +757,30 @@ func (api *API) workspaceAgentReportStats(rw http.ResponseWriter, r *http.Reques
 
 	// Allow overriding the stat interval for debugging and testing purposes.
 	timer := time.NewTicker(api.AgentStatsRefreshInterval)
-	for {
-		err := wsjson.Write(ctx, conn, codersdk.AgentStatsReportRequest{})
-		if err != nil {
-			api.Logger.Debug(ctx, "write report request", slog.Error(err))
-			conn.Close(websocket.StatusInternalError, httpapi.WebsocketCloseSprintf("write report request: %s", err))
-			return
+	defer timer.Stop()
+
+	go func() {
+		for {
+			err = wsjson.Write(ctx, conn, codersdk.AgentStatsReportRequest{})
+			if err != nil {
+				conn.Close(websocket.StatusInternalError, httpapi.WebsocketCloseSprintf("write report request: %s", err))
+				return
+			}
+
+			select {
+			case <-timer.C:
+				continue
+			case <-ctx.Done():
+				conn.Close(websocket.StatusNormalClosure, "")
+				return
+			}
 		}
-		var rep codersdk.AgentStatsReportResponse
+	}()
 
+	for {
+		var rep codersdk.AgentStatsReportResponse
 		err = wsjson.Read(ctx, conn, &rep)
 		if err != nil {
-			api.Logger.Debug(ctx, "read report response", slog.Error(err))
 			conn.Close(websocket.StatusInternalError, httpapi.WebsocketCloseSprintf("read report response: %s", err))
 			return
 		}
@@ -827,14 +839,6 @@ func (api *API) workspaceAgentReportStats(rw http.ResponseWriter, r *http.Reques
 				return
 			}
 		}
-
-		select {
-		case <-timer.C:
-			continue
-		case <-ctx.Done():
-			conn.Close(websocket.StatusNormalClosure, "")
-			return
-		}
 	}
 }
 
