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grpc: move to TransientFailure in pick_first LB policy when all addresses are removed #5274

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Merged
merged 5 commits into from
Mar 29, 2022
Merged

grpc: move to TransientFailure in pick_first LB policy when all addresses are removed #5274

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cdf3089
grpc: move to TransientFailure from pickfirst LB policy when all addr…
easwars Mar 25, 2022
8da1950
rename sc to subConn
easwars Mar 25, 2022
5fb5259
review comments
easwars Mar 25, 2022
e03d2d4
more variable renaming
easwars Mar 25, 2022
8574c0c
remove parameter
easwars Mar 29, 2022
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28 changes: 21 additions & 7 deletions pickfirst.go
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Original file line number Diff line number Diff line change
Expand Up @@ -50,23 +50,37 @@ type pickfirstBalancer struct {
}

func (b *pickfirstBalancer) ResolverError(err error) {
switch b.state {
case connectivity.TransientFailure, connectivity.Idle, connectivity.Connecting:
// Set a failing picker if we don't have a good picker.
b.cc.UpdateState(balancer.State{ConnectivityState: connectivity.TransientFailure,
Picker: &picker{err: fmt.Errorf("name resolver error: %v", err)},
})
}
if logger.V(2) {
logger.Infof("pickfirstBalancer: ResolverError called with error %v", err)
}
if b.sc == nil {
b.state = connectivity.TransientFailure
}

if b.state != connectivity.TransientFailure {
// The picker will not change since the balancer does not currently
// report an error.
return
}
b.cc.UpdateState(balancer.State{
ConnectivityState: connectivity.TransientFailure,
Picker: &picker{err: fmt.Errorf("name resolver error: %v", err)},
})
}

func (b *pickfirstBalancer) UpdateClientConnState(cs balancer.ClientConnState) error {
if len(cs.ResolverState.Addresses) == 0 {
if b.sc != nil {
// If the resolver returned empty addresses after it gave us non-empty
// addresses, we need to close the existing subConn. Setting sc to nil
// here will cause us to return an error picker from ResolverError().
b.cc.RemoveSubConn(b.sc)
b.sc = nil
}
b.ResolverError(errors.New("produced zero addresses"))
return balancer.ErrBadResolverState
}

if b.sc == nil {
var err error
b.sc, err = b.cc.NewSubConn(cs.ResolverState.Addresses, balancer.NewSubConnOptions{})
Expand Down
82 changes: 0 additions & 82 deletions test/balancer_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,6 @@ import (
"google.golang.org/grpc"
"google.golang.org/grpc/attributes"
"google.golang.org/grpc/balancer"
"google.golang.org/grpc/balancer/roundrobin"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/credentials"
Expand Down Expand Up @@ -683,87 +682,6 @@ func (s) TestServersSwap(t *testing.T) {
}
}

// TestEmptyAddrs verifies client behavior when a working connection is
// removed. In pick first and round-robin, both will continue using the old
// connections.
Comment on lines -686 to -688
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Let's make sure there's still a test for this set of circumstances, but that the RPCs begin failing instead of keep using old connections.

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Also, I thought we confirmed RR was removing the subconns, so RPCs should have been failing? But this test is validating the RPCs would still succeed?

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Also, I thought we confirmed RR was removing the subconns, so RPCs should have been failing? But this test is validating the RPCs would still succeed?

Yes, this test was quite broken because it was using the pick_first clientConn to verify round_robin behaviour:

	// Confirm several new RPCs succeed on round robin.
	for i := 0; i < 10; i++ {
		if _, err := pfclient.UnaryCall(ctx, &testpb.SimpleRequest{}); err != nil {
			t.Fatalf("UnaryCall(_) = _, %v; want _, nil", err)
		}
		time.Sleep(5 * time.Millisecond)
	}

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Let's make sure there's still a test for this set of circumstances, but that the RPCs begin failing instead of keep using old connections.

Yes, the newly added test verifies that the channel moves to TransientFailure when addresses are removed and that a WaitForReady RPC blocks until new addresses are added.

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Yes, this test was quite broken because it was using the pick_first clientConn to verify round_robin behaviour:

Oof

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Yes, the newly added test verifies that the channel moves to TransientFailure when addresses are removed and that a WaitForReady RPC blocks until new addresses are added.

But only with pick first -- is there one for RR too elsewhere?

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We do have a couple of tests for round_robin that I recently cleaned up:
1
2

func (s) TestEmptyAddrs(t *testing.T) {
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

// Initialize server
lis, err := net.Listen("tcp", "localhost:0")
if err != nil {
t.Fatalf("Error while listening. Err: %v", err)
}
s := grpc.NewServer()
defer s.Stop()
const one = "1"
ts := &funcServer{
unaryCall: func(ctx context.Context, in *testpb.SimpleRequest) (*testpb.SimpleResponse, error) {
return &testpb.SimpleResponse{Username: one}, nil
},
}
testpb.RegisterTestServiceServer(s, ts)
go s.Serve(lis)

// Initialize pickfirst client
pfr := manual.NewBuilderWithScheme("whatever")

pfr.InitialState(resolver.State{Addresses: []resolver.Address{{Addr: lis.Addr().String()}}})

pfcc, err := grpc.DialContext(ctx, pfr.Scheme()+":///", grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithResolvers(pfr))
if err != nil {
t.Fatalf("Error creating client: %v", err)
}
defer pfcc.Close()
pfclient := testpb.NewTestServiceClient(pfcc)

// Confirm we are connected to the server
if res, err := pfclient.UnaryCall(ctx, &testpb.SimpleRequest{}); err != nil || res.Username != one {
t.Fatalf("UnaryCall(_) = %v, %v; want {Username: %q}, nil", res, err, one)
}

// Remove all addresses.
pfr.UpdateState(resolver.State{})

// Initialize roundrobin client
rrr := manual.NewBuilderWithScheme("whatever")

rrr.InitialState(resolver.State{Addresses: []resolver.Address{{Addr: lis.Addr().String()}}})

rrcc, err := grpc.DialContext(ctx, rrr.Scheme()+":///", grpc.WithTransportCredentials(insecure.NewCredentials()), grpc.WithResolvers(rrr),
grpc.WithDefaultServiceConfig(fmt.Sprintf(`{ "loadBalancingConfig": [{"%v": {}}] }`, roundrobin.Name)))
if err != nil {
t.Fatalf("Error creating client: %v", err)
}
defer rrcc.Close()
rrclient := testpb.NewTestServiceClient(rrcc)

// Confirm we are connected to the server
if res, err := rrclient.UnaryCall(ctx, &testpb.SimpleRequest{}); err != nil || res.Username != one {
t.Fatalf("UnaryCall(_) = %v, %v; want {Username: %q}, nil", res, err, one)
}

// Remove all addresses.
rrr.UpdateState(resolver.State{})

// Confirm several new RPCs succeed on pick first.
for i := 0; i < 10; i++ {
if _, err := pfclient.UnaryCall(ctx, &testpb.SimpleRequest{}); err != nil {
t.Fatalf("UnaryCall(_) = _, %v; want _, nil", err)
}
time.Sleep(5 * time.Millisecond)
}

// Confirm several new RPCs succeed on round robin.
for i := 0; i < 10; i++ {
if _, err := pfclient.UnaryCall(ctx, &testpb.SimpleRequest{}); err != nil {
t.Fatalf("UnaryCall(_) = _, %v; want _, nil", err)
}
time.Sleep(5 * time.Millisecond)
}
}

func (s) TestWaitForReady(t *testing.T) {
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
Expand Down
74 changes: 74 additions & 0 deletions test/pickfirst_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,9 @@ import (

"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/connectivity"
"google.golang.org/grpc/credentials/insecure"
"google.golang.org/grpc/internal/channelz"
"google.golang.org/grpc/internal/stubserver"
"google.golang.org/grpc/peer"
"google.golang.org/grpc/resolver"
Expand All @@ -43,6 +45,11 @@ const pickFirstServiceConfig = `{"loadBalancingConfig": [{"pick_first":{}}]}`
// with service config specifying the use of the pick_first LB policy.
func setupPickFirst(t *testing.T, backendCount int, opts ...grpc.DialOption) (*grpc.ClientConn, *manual.Resolver, []*stubserver.StubServer) {
t.Helper()

// Initialize channelz. Used to determine pending RPC count.
czCleanup := channelz.NewChannelzStorageForTesting()
t.Cleanup(func() { czCleanupWrapper(czCleanup, t) })

r := manual.NewBuilderWithScheme("whatever")

backends := make([]*stubserver.StubServer, backendCount)
Expand Down Expand Up @@ -258,3 +265,70 @@ func (s) TestPickFirst_AddressesRemoved(t *testing.T) {
t.Fatal(err)
}
}

// TestPickFirst_NewAddressWhileBlocking tests the case where pick_first is
// configured on a channel, things are working as expected and then a resolver
// updates removes all addresses. An RPC attempted at this point in time will be
// blocked because there are no valid backends. This test verifies that when new
// backends are added, the RPC is able to complete.
func (s) TestPickFirst_NewAddressWhileBlocking(t *testing.T) {
cc, r, backends := setupPickFirst(t, 2)
addrs := backendsToAddrs(backends)
r.UpdateState(resolver.State{Addresses: addrs})

ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
defer cancel()
if err := checkPickFirst(ctx, cc, addrs[0].Addr); err != nil {
t.Fatal(err)
}

// Send a resolver update with no addresses. This should push the channel into
// TransientFailure.
r.UpdateState(resolver.State{})
for state := cc.GetState(); state != connectivity.TransientFailure; state = cc.GetState() {
if !cc.WaitForStateChange(ctx, state) {
t.Fatalf("timeout waiting for state change. got %v; want %v", state, connectivity.TransientFailure)
}
}

doneCh := make(chan struct{})
client := testpb.NewTestServiceClient(cc)
go func() {
// The channel is currently in TransientFailure and this RPC will block
// until the channel becomes Ready, which will only happen when we push a
// resolver update with a valid backend address.
if _, err := client.EmptyCall(ctx, &testpb.Empty{}, grpc.WaitForReady(true)); err != nil {
t.Errorf("EmptyCall() = %v, want <nil>", err)
}
close(doneCh)
}()

// Make sure that there is one pending RPC on the ClientConn before attempting
// to push new addresses through the name resolver. If we don't do this, the
// resolver update can happen before the above goroutine gets to make the RPC.
for {
if err := ctx.Err(); err != nil {
t.Fatal(err)
}
tcs, _ := channelz.GetTopChannels(0, 0)
if len(tcs) != 1 {
t.Fatalf("there should only be one top channel, not %d", len(tcs))
}
started := tcs[0].ChannelData.CallsStarted
completed := tcs[0].ChannelData.CallsSucceeded + tcs[0].ChannelData.CallsFailed
if (started - completed) == 1 {
break
}
time.Sleep(defaultTestShortTimeout)
}

// Send a resolver update with a valid backend to push the channel to Ready
// and unblock the above RPC.
r.UpdateState(resolver.State{Addresses: []resolver.Address{{Addr: backends[0].Address}}})

select {
case <-ctx.Done():
t.Fatal("Timeout when waiting for blocked RPC to complete")
case <-doneCh:
}
}