From 95c834a73ce334a18ab12e5db19324700bcdca0e Mon Sep 17 00:00:00 2001
From: Menghan Li <menghanl@google.com>
Date: Wed, 12 Feb 2020 11:11:21 -0800
Subject: [PATCH] xds: resolver handle good update after getting an error
 (#3374)

---
 xds/internal/resolver/xds_resolver.go      |  2 +-
 xds/internal/resolver/xds_resolver_test.go | 47 ++++++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/xds/internal/resolver/xds_resolver.go b/xds/internal/resolver/xds_resolver.go
index f116eff9..2ac72b2c 100644
--- a/xds/internal/resolver/xds_resolver.go
+++ b/xds/internal/resolver/xds_resolver.go
@@ -171,7 +171,7 @@ func (r *xdsResolver) run() {
 		case update := <-r.updateCh:
 			if update.err != nil {
 				r.cc.ReportError(update.err)
-				return
+				continue
 			}
 			sc := fmt.Sprintf(jsonFormatSC, update.su.Cluster)
 			r.cc.UpdateState(resolver.State{
diff --git a/xds/internal/resolver/xds_resolver_test.go b/xds/internal/resolver/xds_resolver_test.go
index 62c4576f..7dbe7167 100644
--- a/xds/internal/resolver/xds_resolver_test.go
+++ b/xds/internal/resolver/xds_resolver_test.go
@@ -324,3 +324,50 @@ func TestXDSResolverGoodServiceUpdate(t *testing.T) {
 		t.Fatalf("ClientConn.UpdateState received error in service config: %v", rState.ServiceConfig.Err)
 	}
 }
+
+// TestXDSResolverUpdates tests the cases where the resolver gets a good update
+// after an error, and an error after the good update.
+func TestXDSResolverGoodUpdateAfterError(t *testing.T) {
+	xdsC := fakeclient.NewClient()
+	xdsR, tcc, cancel := testSetup(t, setupOpts{
+		config:        &validConfig,
+		xdsClientFunc: func(_ xdsclient.Options) (xdsClientInterface, error) { return xdsC, nil },
+	})
+	defer func() {
+		cancel()
+		xdsR.Close()
+	}()
+
+	waitForWatchService(t, xdsC, targetStr)
+
+	// Invoke the watchAPI callback with a bad service update and wait for the
+	// ReportError method to be called on the ClientConn.
+	suErr := errors.New("bad serviceupdate")
+	xdsC.InvokeWatchServiceCallback("", suErr)
+	if gotErrVal, gotErr := tcc.errorCh.Receive(); gotErr != nil || gotErrVal != suErr {
+		t.Fatalf("ClientConn.ReportError() received %v, want %v", gotErrVal, suErr)
+	}
+
+	// Invoke the watchAPI callback with a good service update and wait for the
+	// UpdateState method to be called on the ClientConn.
+	xdsC.InvokeWatchServiceCallback(cluster, nil)
+	gotState, err := tcc.stateCh.Receive()
+	if err != nil {
+		t.Fatalf("ClientConn.UpdateState returned error: %v", err)
+	}
+	rState := gotState.(resolver.State)
+	if gotClient := rState.Attributes.Value(xdsinternal.XDSClientID); gotClient != xdsC {
+		t.Fatalf("ClientConn.UpdateState got xdsClient: %v, want %v", gotClient, xdsC)
+	}
+	if err := rState.ServiceConfig.Err; err != nil {
+		t.Fatalf("ClientConn.UpdateState received error in service config: %v", rState.ServiceConfig.Err)
+	}
+
+	// Invoke the watchAPI callback with a bad service update and wait for the
+	// ReportError method to be called on the ClientConn.
+	suErr2 := errors.New("bad serviceupdate 2")
+	xdsC.InvokeWatchServiceCallback("", suErr2)
+	if gotErrVal, gotErr := tcc.errorCh.Receive(); gotErr != nil || gotErrVal != suErr2 {
+		t.Fatalf("ClientConn.ReportError() received %v, want %v", gotErrVal, suErr2)
+	}
+}