From 69cbd562e354bd1c296da6585c3999c2c13eadd2 Mon Sep 17 00:00:00 2001
From: lillian <lillian@fly.io>
Date: Mon, 13 Jul 2026 18:43:01 +0000
Subject: [PATCH] Report agent WireGuard transport metric (udp vs websocket)

The agent now reports which transport it used to establish a WireGuard
tunnel (plain UDP or the websocket proxy) to flyctl-metrics via a new
agent_wireguard/transport metric.

Since the agent is a long-lived daemon that never reaches the
end-of-command metrics flush, this adds metrics.SendImmediate, which
posts a single-message batch right away through the existing
SendMetrics path (respecting send_metrics config, the dev-build guard,
and metrics-token handling).

Collector side: superfly/flyctl-metrics agent-wireguard-transport-metric

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
---
 agent/server/server.go      |  8 ++++++++
 internal/metrics/api.go     | 29 +++++++++++++++++++++++++++++
 internal/metrics/helpers.go |  7 +++++++
 3 files changed, 44 insertions(+)

diff --git a/agent/server/server.go b/agent/server/server.go
index d00b11a56d..f026a61e9b 100644
--- a/agent/server/server.go
+++ b/agent/server/server.go
@@ -19,6 +19,7 @@ import (
 	"github.com/superfly/flyctl/internal/config"
 	"github.com/superfly/flyctl/internal/env"
 	"github.com/superfly/flyctl/internal/flyutil"
+	"github.com/superfly/flyctl/internal/metrics"
 	"github.com/superfly/flyctl/internal/metrics/synthetics"
 	"github.com/superfly/flyctl/internal/sentry"
 	"github.com/superfly/flyctl/internal/wireguard"
@@ -245,7 +246,10 @@ func (s *server) buildTunnel(ctx context.Context, org *fly.Organization, reestab
 	}
 
 	// WIP: can't stay this way, need something more clever than this
+	transport := "udp"
 	if env.IsCI() || os.Getenv("WSWG") != "" || s.ConfigWebsockets {
+		transport = "websocket"
+
 		if tunnel, err = wg.ConnectWS(ctx, state); err != nil {
 			return
 		}
@@ -255,6 +259,10 @@ func (s *server) buildTunnel(ctx context.Context, org *fly.Organization, reestab
 		}
 	}
 
+	// use the agent's run context: the session context may be gone before the
+	// send completes
+	metrics.AgentWireGuardTransport(s.runCtx, transport)
+
 	s.tunnels[tk] = tunnel
 
 	return
diff --git a/internal/metrics/api.go b/internal/metrics/api.go
index 34681c3d2b..86c94e38c0 100644
--- a/internal/metrics/api.go
+++ b/internal/metrics/api.go
@@ -32,6 +32,35 @@ func rawSend(parentCtx context.Context, metricSlug string, payload json.RawMessa
 	queueMetric(message)
 }
 
+// SendImmediate sends a single metric to the collector right away instead of
+// queueing it for the end-of-command flush. Long-running processes (e.g. the
+// agent) queue metrics that would otherwise never be flushed.
+func SendImmediate[T any](ctx context.Context, metricSlug string, value T) {
+	if !shouldSendMetrics(ctx) {
+		return
+	}
+
+	payload, err := json.Marshal(value)
+	if err != nil {
+		return
+	}
+
+	buf, err := json.Marshal([]metricsMessage{{
+		Metric:  metricSlug,
+		Payload: payload,
+	}})
+	if err != nil {
+		return
+	}
+
+	done.Add(1)
+	go func() {
+		defer done.Done()
+
+		_ = SendMetrics(ctx, string(buf))
+	}()
+}
+
 func shouldSendMetrics(ctx context.Context) bool {
 	if !Enabled {
 		return false
diff --git a/internal/metrics/helpers.go b/internal/metrics/helpers.go
index 32dc03fde7..ea9d65ad38 100644
--- a/internal/metrics/helpers.go
+++ b/internal/metrics/helpers.go
@@ -140,6 +140,13 @@ func DeployStatus(ctx context.Context, payload DeployStatusPayload) {
 	Send(ctx, "deploy/status", payload)
 }
 
+// AgentWireGuardTransport reports which transport the agent used to establish
+// a WireGuard tunnel: "udp" or "websocket". It sends immediately because the
+// agent daemon never reaches the end-of-command metrics flush.
+func AgentWireGuardTransport(ctx context.Context, transport string) {
+	SendImmediate(ctx, "agent_wireguard/transport", map[string]string{"transport": transport})
+}
+
 func Send[T any](ctx context.Context, metricSlug string, value T) {
 	valJson, err := json.Marshal(value)
 	if err != nil {