chore: Implement workspace proxy going away (graceful shutdown) (#7459)

* chore: Implement workspace proxy going away

When a workspace proxy shuts down, the health status of that
proxy should immediately be updated. This is purely a courtesy
and technically not required

enterprise/coderd/workspaceproxy_test.go

@@ -7,6 +7,7 @@ import (
 	"net/http/httputil"
 	"net/url"
 	"testing"
+	"time"
 
 	"github.com/google/uuid"
 	"github.com/moby/moby/pkg/namesgenerator"
@@ -172,6 +173,69 @@ func TestRegions(t *testing.T) {
 		require.Error(t, err)
 		require.Empty(t, regions)
 	})
+
+	t.Run("GoingAway", func(t *testing.T) {
+		t.Parallel()
+
+		dv := coderdtest.DeploymentValues(t)
+		dv.Experiments = []string{
+			string(codersdk.ExperimentMoons),
+			"*",
+		}
+
+		db, pubsub := dbtestutil.NewDB(t)
+
+		ctx := testutil.Context(t, testutil.WaitLong)
+
+		client, closer, api := coderdenttest.NewWithAPI(t, &coderdenttest.Options{
+			Options: &coderdtest.Options{
+				AppHostname:      appHostname,
+				Database:         db,
+				Pubsub:           pubsub,
+				DeploymentValues: dv,
+			},
+			// The interval is set to 1 hour so the proxy health
+			// check will never happen manually. All checks will be
+			// forced updates.
+			ProxyHealthInterval: time.Hour,
+		})
+		t.Cleanup(func() {
+			_ = closer.Close()
+		})
+		_ = coderdtest.CreateFirstUser(t, client)
+		_ = coderdenttest.AddLicense(t, client, coderdenttest.LicenseOptions{
+			Features: license.Features{
+				codersdk.FeatureWorkspaceProxy: 1,
+			},
+		})
+
+		const proxyName = "testproxy"
+		proxy := coderdenttest.NewWorkspaceProxy(t, api, client, &coderdenttest.ProxyOptions{
+			Name: proxyName,
+		})
+		_ = proxy
+
+		require.Eventuallyf(t, func() bool {
+			proxy, err := client.WorkspaceProxyByName(ctx, proxyName)
+			if err != nil {
+				// We are testing the going away, not the initial healthy.
+				// Just force an update to change this to healthy.
+				_ = api.ProxyHealth.ForceUpdate(ctx)
+				return false
+			}
+			return proxy.Status.Status == codersdk.ProxyHealthy
+		}, testutil.WaitShort, testutil.IntervalFast, "proxy never became healthy")
+
+		_ = proxy.Close()
+		// The proxy should tell the primary on close that is is no longer healthy.
+		require.Eventuallyf(t, func() bool {
+			proxy, err := client.WorkspaceProxyByName(ctx, proxyName)
+			if err != nil {
+				return false
+			}
+			return proxy.Status.Status == codersdk.ProxyUnhealthy
+		}, testutil.WaitShort, testutil.IntervalFast, "proxy never became unhealthy after close")
+	})
 }
 
 func TestWorkspaceProxyCRUD(t *testing.T) {