From b3d8ab77191e914807a771bc96a4b5aea917dc00 Mon Sep 17 00:00:00 2001
From: Colin Adler <colin1adler@gmail.com>
Date: Mon, 17 Oct 2022 18:31:29 -0500
Subject: [PATCH] fix: agent stats websocket blocking until next interval

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.
---
 coderd/workspaceagents.go | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/coderd/workspaceagents.go b/coderd/workspaceagents.go
index fb7f765cc7519..250b4c73ae3f9 100644
--- 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
-		}
 	}
 }