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[ADDED] StatusChanged for core and js subscriptions #1570

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merged 5 commits into from
Mar 11, 2024
Merged

[ADDED] StatusChanged for core and js subscriptions #1570

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075667d
[ADDED] DrainStatus for core and js subscriptions
piotrpio Feb 26, 2024
531b807
Removed DrainStatus
piotrpio Feb 27, 2024
ad743b5
[ADDED] StatusChanged listeners for subscription
piotrpio Mar 1, 2024
0a2885d
Close event channels on subscription close
piotrpio Mar 11, 2024
7663664
Fix race when changing sub status
piotrpio Mar 11, 2024
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87 changes: 79 additions & 8 deletions nats.go
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Original file line number Diff line number Diff line change
Expand Up @@ -608,14 +608,16 @@ type Subscription struct {
// For holding information about a JetStream consumer.
jsi *jsSub

delivered uint64
max uint64
conn *Conn
mcb MsgHandler
mch chan *Msg
closed bool
sc bool
connClosed bool
delivered uint64
max uint64
conn *Conn
mcb MsgHandler
mch chan *Msg
closed bool
sc bool
connClosed bool
draining bool
drainingComplete chan struct{}

// Type of Subscription
typ SubscriptionType
Expand Down Expand Up @@ -4410,6 +4412,65 @@ func (s *Subscription) Drain() error {
return conn.unsubscribe(s, 0, true)
}

type DrainStatus interface {
PendingMsgs() int
Draining() bool
Complete() <-chan struct{}
}

type drainStatus struct {
sub *Subscription
}

func (s *Subscription) DrainStatus() DrainStatus {
s.mu.Lock()
defer s.mu.Unlock()
return &drainStatus{
sub: s,
}
}

func (s *drainStatus) Draining() bool {
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could be part of subscription state instead sub.IsDraining maybe? like the sub companion for nc.IsDraining

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Yes, I suppose getting rid of DrainStatus() method and hanging everything off from Subscription is a good call. At first I had a different idea around structuring it and left the API it as it was. I'll change that.

if s.sub == nil {
return false
}
s.sub.mu.Lock()
defer s.sub.mu.Unlock()
return s.sub.draining
}

func (s *drainStatus) Complete() <-chan struct{} {
var drainCh chan struct{}
if s.sub == nil {
// if the subscription is nil, return a closed channel
// to avoid blocking on the caller side.
drainCh = make(chan struct{})
close(drainCh)
return drainCh
}
s.sub.mu.Lock()
defer s.sub.mu.Unlock()
if s.sub.drainingComplete == nil {
drainCh = make(chan struct{})
s.sub.drainingComplete = drainCh
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drainingComplete maybe too long, could be instead sub.drainCh like here or sub.dch

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drainCh sounds good, I'll change it. dch is a bit too ambiguous for my liking.

} else {
drainCh = s.sub.drainingComplete
}
if !s.sub.draining {
// if the subscription is not draining, close the channel
// immediately to avoid blocking on the caller side.
close(drainCh)
s.sub.drainingComplete = nil
}
return drainCh
}

func (s *drainStatus) PendingMsgs() int {
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can get this from sub.Pending() already for both PendingMsgs abd PendingBytes, maybe not needed?

s.sub.mu.Lock()
defer s.sub.mu.Unlock()
return s.sub.pMsgs
}

// Unsubscribe will remove interest in the given subject.
//
// For a JetStream subscription, if the library has created the JetStream
Expand Down Expand Up @@ -4448,6 +4509,15 @@ func (s *Subscription) Unsubscribe() error {
// checkDrained will watch for a subscription to be fully drained
// and then remove it.
func (nc *Conn) checkDrained(sub *Subscription) {
defer func() {
sub.mu.Lock()
defer sub.mu.Unlock()
sub.draining = false
if sub.drainingComplete != nil {
close(sub.drainingComplete)
sub.drainingComplete = nil
}
}()
if nc == nil || sub == nil {
return
}
Expand Down Expand Up @@ -4557,6 +4627,7 @@ func (nc *Conn) unsubscribe(sub *Subscription, max int, drainMode bool) error {
}

if drainMode {
s.draining = true
go nc.checkDrained(sub)
}

Expand Down
270 changes: 270 additions & 0 deletions test/drain_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -486,3 +486,273 @@ func TestDrainConnDuringReconnect(t *testing.T) {
t.Fatalf("Timeout waiting for closed state for connection")
}
}

func TestDrainStatus(t *testing.T) {
t.Run("subscribe", func(t *testing.T) {
s := RunDefaultServer()
defer s.Shutdown()

nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
t.Fatalf("Failed to create default connection: %v", err)
}
defer nc.Close()

if nc.IsDraining() {
t.Fatalf("Expected IsDraining to be false")
}

sub, err := nc.Subscribe("foo", func(_ *nats.Msg) {
time.Sleep(10 * time.Millisecond)
})
if err != nil {
t.Fatalf("Error creating subscription; %v", err)
}
for i := 0; i < 100; i++ {
nc.Publish("foo", []byte("hello"))
}
time.Sleep(100 * time.Millisecond)
sub.Drain()
ds := sub.DrainStatus()
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maybe later can have some helper build on top like sub.WaitDrained(ctx) error that waits for drain to complete or timeout.

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Yeah, that's a good idea. Not sure I want to add it in this PR though, it's easy enough to implement it yourself and I want to be careful about adding public APIs.

In the future though, that might be useful.


if !ds.Draining() {
t.Fatalf("Expected to be draining")
}
if ds.PendingMsgs() == 0 {
t.Fatalf("Expected pending messages")
}

select {
case <-ds.Complete():
if ds.PendingMsgs() != 0 {
t.Fatalf("Expected no pending messages")
}
if ds.Draining() {
t.Fatalf("Expected to be drained")
}
case <-time.After(10 * time.Second):
t.Fatalf("Timeout waiting for drain to complete")
}
})

t.Run("subscribe sync", func(t *testing.T) {
s := RunDefaultServer()
defer s.Shutdown()

nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
t.Fatalf("Failed to create default connection: %v", err)
}
defer nc.Close()

if nc.IsDraining() {
t.Fatalf("Expected IsDraining to be false")
}

sub, err := nc.SubscribeSync("foo")
if err != nil {
t.Fatalf("Error creating subscription; %v", err)
}
for i := 0; i < 100; i++ {
nc.Publish("foo", []byte("hello"))
}
time.Sleep(100 * time.Millisecond)
sub.Drain()
ds := sub.DrainStatus()

if !ds.Draining() {
t.Fatalf("Expected to be draining")
}
if ds.PendingMsgs() == 0 {
t.Fatalf("Expected pending messages")
}
for i := 0; i < 100; i++ {
_, err := sub.NextMsg(time.Second)
if err != nil {
t.Fatalf("Error getting message: %v", err)
}
}

select {
case <-ds.Complete():
if ds.PendingMsgs() != 0 {
t.Fatalf("Expected no pending messages")
}
if ds.Draining() {
t.Fatalf("Expected to be drained")
}
case <-time.After(10 * time.Second):
t.Fatalf("Timeout waiting for drain to complete")
}
})

t.Run("chan subscribe", func(t *testing.T) {
s := RunDefaultServer()
defer s.Shutdown()

nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
t.Fatalf("Failed to create default connection: %v", err)
}
defer nc.Close()

if nc.IsDraining() {
t.Fatalf("Expected IsDraining to be false")
}

ch := make(chan *nats.Msg, 100)
sub, err := nc.ChanSubscribe("foo", ch)
if err != nil {
t.Fatalf("Error creating subscription; %v", err)
}
for i := 0; i < 100; i++ {
nc.Publish("foo", []byte("hello"))
}
time.Sleep(100 * time.Millisecond)
sub.Drain()
ds := sub.DrainStatus()

select {
case <-ds.Complete():
if ds.PendingMsgs() != 0 {
t.Fatalf("Expected no pending messages")
}
if ds.Draining() {
t.Fatalf("Expected to be drained")
}
case <-time.After(10 * time.Second):
t.Fatalf("Timeout waiting for drain to complete")
}

// msgs should be available on the channel
for i := 0; i < 100; i++ {
select {
case <-ch:
case <-time.After(2 * time.Second):
t.Fatalf("Timeout waiting for message")
}
}
})

t.Run("subscription not draining", func(t *testing.T) {
s := RunDefaultServer()
defer s.Shutdown()

nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
t.Fatalf("Failed to create default connection: %v", err)
}
defer nc.Close()

sub, err := nc.Subscribe("foo", func(_ *nats.Msg) {
time.Sleep(10 * time.Millisecond)
})
if err != nil {
t.Fatalf("Error creating subscription; %v", err)
}
ds := sub.DrainStatus()

if ds.Draining() {
t.Fatalf("Expected not to be draining")
}
if ds.PendingMsgs() != 0 {
t.Fatalf("Expected no pending messages")
}
select {
case <-ds.Complete():
default:
t.Fatalf("Expected to be complete")
}
})

t.Run("subscription already unsubscribed", func(t *testing.T) {
s := RunDefaultServer()
defer s.Shutdown()

nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
t.Fatalf("Failed to create default connection: %v", err)
}
defer nc.Close()

sub, err := nc.Subscribe("foo", func(_ *nats.Msg) {})
if err != nil {
t.Fatalf("Error creating subscription; %v", err)
}
sub.Unsubscribe()
ds := sub.DrainStatus()

if ds.Draining() {
t.Fatalf("Expected not to be draining")
}
if ds.PendingMsgs() != 0 {
t.Fatalf("Expected no pending messages")
}

select {
case <-ds.Complete():
default:
t.Fatalf("Expected to be complete")
}
})
}

func TestDrainStatus_ConcurrentComplete(t *testing.T) {
s := RunDefaultServer()
defer s.Shutdown()

nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
t.Fatalf("Failed to create default connection: %v", err)
}
defer nc.Close()

sub, err := nc.Subscribe("foo", func(_ *nats.Msg) {
time.Sleep(20 * time.Millisecond)
})
if err != nil {
t.Fatalf("Error creating subscription; %v", err)
}
for i := 0; i < 100; i++ {
nc.Publish("foo", []byte("hello"))
}
time.Sleep(100 * time.Millisecond)
sub.Drain()
wg := sync.WaitGroup{}
wg.Add(10)
done := make(chan struct{})
errs := make(chan error)
for i := 0; i < 10; i++ {
go func() {
ds := sub.DrainStatus()
<-ds.Complete()
if ds.PendingMsgs() != 0 {
errs <- fmt.Errorf("Expected no pending messages")
}
if ds.Draining() {
errs <- fmt.Errorf("Expected to be drained")
}
wg.Done()
}()
}
go func() {
wg.Wait()
close(done)
}()

// if !ds.Draining() {
// t.Fatalf("Expected to be draining")
// }
// if ds.PendingMsgs() == 0 {
// t.Fatalf("Expected pending messages")
// }

// Now test concurrent calls to DrainStatus
select {
case <-done:
case err := <-errs:
t.Fatal(err)
case <-time.After(10 * time.Second):
t.Fatalf("Timeout waiting for drain to complete")
}
}
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