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Add option to set memory storage to true for a consumer #1078

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merged 3 commits into from Sep 15, 2022
Merged

Add option to set memory storage to true for a consumer #1078

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8450fa7
Add option to set memory storage to true for a consumer
Sep 14, 2022
8f89f51
Add a check in checkConfig
Sep 14, 2022
b64c208
Rename SetMemoryStorage to ConsumerMemoryStorage
Sep 15, 2022
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5 changes: 5 additions & 0 deletions example_test.go
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Expand Up @@ -630,6 +630,11 @@ func ExampleSubOpt() {
js.Subscribe("foo", func(msg *nats.Msg) {
fmt.Printf("Received a message: %s\n", string(msg.Data))
}, nats.Durable("FOO"), nats.ConsumerReplicas(1))

// Force memory storage while subscribing.
js.Subscribe("foo", func(msg *nats.Msg) {
fmt.Printf("Received a message: %s\n", string(msg.Data))
}, nats.Durable("FOO"), nats.ConsumerMemoryStorage())
}

func ExampleMaxWait() {
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11 changes: 11 additions & 0 deletions js.go
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Expand Up @@ -1357,6 +1357,9 @@ func checkConfig(s, u *ConsumerConfig) error {
if u.Replicas > 0 && u.Replicas != s.Replicas {
return makeErr("replicas", u.Replicas, s.Replicas)
}
if u.MemoryStorage && !s.MemoryStorage {
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I think we should be verifying it both ways, i.e. true -> false and false -> true. Right now check will pass even if u.MemoryStorage == false and s.MemoryStorage == true.

Suggested change
if u.MemoryStorage && !s.MemoryStorage {
if u.MemoryStorage != !s.MemoryStorage {

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No we can't unfortunately, because we don't have a "3 states" value: true, false, not-specified. The point of this function is to check the user intent vs what is already configured in the server.
We have no way to express that the user does not want MemoryStorage, so if you call js.Subscribe() without specifying anything and the JS consumer happens to be configured on the server with MemoryStorage, you don't want to call to fail. Otherwise we would need an option that says "NoMemoryStorage", etc..

So this function for boolean is not great, but the best we can do is check when the intent was to set a boolean to true, then only we can check that it matches the server setting.

return makeErr("memory storage", u.MemoryStorage, s.MemoryStorage)
}
return nil
}

Expand Down Expand Up @@ -2485,6 +2488,14 @@ func ConsumerReplicas(replicas int) SubOpt {
})
}

// ConsumerMemoryStorage sets the memory storage to true for a consumer.
func ConsumerMemoryStorage() SubOpt {
return subOptFn(func(opts *subOpts) error {
opts.cfg.MemoryStorage = true
return nil
})
}

func (sub *Subscription) ConsumerInfo() (*ConsumerInfo, error) {
sub.mu.Lock()
// TODO(dlc) - Better way to mark especially if we attach.
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61 changes: 61 additions & 0 deletions js_test.go
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Expand Up @@ -1096,3 +1096,64 @@ func TestJetStreamConvertDirectMsgResponseToMsg(t *testing.T) {
t.Fatalf("Wrong header: %v", r.Header)
}
}

func TestJetStreamConsumerMemoryStorage(t *testing.T) {
opts := natsserver.DefaultTestOptions
opts.Port = -1
opts.JetStream = true
s := natsserver.RunServer(&opts)
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You can just use s := RunBasicJetStreamServer() instead.

defer shutdownJSServerAndRemoveStorage(t, s)

nc, js := jsClient(t, s)
defer nc.Close()

if _, err := js.AddStream(&StreamConfig{Name: "STR", Subjects: []string{"foo"}}); err != nil {
t.Fatalf("Error adding stream: %v", err)
}

// Pull ephemeral consumer with memory storage.
sub, err := js.PullSubscribe("foo", "", ConsumerMemoryStorage())
if err != nil {
t.Fatalf("Error on subscribe: %v", err)
}

consInfo, err := sub.ConsumerInfo()
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Instead of repeating this code for the 3 types of consumers, I would have made it a small helper function inline:

checkCons := func(sub *Subscription) {
    t.Helper()
    consInfo, err := sub.ConsumerInfo()
    ...
}

then you would invoke it after each sub creation.

if err != nil {
t.Fatalf("Error getting consumer info: %v", err)
}

if !consInfo.Config.MemoryStorage {
t.Fatalf("Expected memory storage to be %v, got %+v", true, consInfo.Config.MemoryStorage)
}

// Create a sync subscription with an in-memory ephemeral consumer.
sub, err = js.SubscribeSync("foo", ConsumerMemoryStorage())
if err != nil {
t.Fatalf("Error on subscribe: %v", err)
}

consInfo, err = sub.ConsumerInfo()
if err != nil {
t.Fatalf("Error getting consumer info: %v", err)
}

if !consInfo.Config.MemoryStorage {
t.Fatalf("Expected memory storage to be %v, got %+v", true, consInfo.Config.MemoryStorage)
}

// Async subscription with an in-memory ephemeral consumer.
cb := func(msg *Msg) {}
sub, err = js.Subscribe("foo", cb, ConsumerMemoryStorage())
if err != nil {
t.Fatalf("Error on subscribe: %v", err)
}

consInfo, err = sub.ConsumerInfo()
if err != nil {
t.Fatalf("Error getting consumer info: %v", err)
}

if !consInfo.Config.MemoryStorage {
t.Fatalf("Expected memory storage to be %v, got %+v", true, consInfo.Config.MemoryStorage)
}
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What you may want to add is a test where a durable is created with MemoryStorage and call a js.SubscribeSync() with Durable() but without the memory storage option in the subscribe call and verifies that it actually works. That would catch the change the Piotr was suggesting that would - in my opinion - break things.

}