natsext

Core NATS Extensions

Core NATS Extensions is a set of utilities providing additional features to Core NATS component of nats.go client.

Installation

go get github.com/synadia-io/orbit.go/natsext

Utilities

RequestMany

RequestMany is a utility that allows you to send a single request and await multiple responses. This allows you to implement various patterns like scatter-gather or streaming responses.

Responses are returned in an iterator, which you can range over to receive messages. When a termination condition is met, the iterator is closed (and no error is returned).

ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
msgs, err := natsext.RequestMany(ctx, nc, "subject", []byte("request data"))
if err != nil {
    // handle error
}
for msg, err := range msgs {
    if err != nil {
        // handle error
    }
    fmt.Println(string(msg.Data))
}

Alternatively, use RequestManyMsg to send a nats.Msg request:

msg := &nats.Msg{
    Subject: "subject",
    Data:    []byte("request data"),
    Header:  nats.Header{
        "Key": []string{"Value"},
    },
}
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
iter, err := natsext.RequestManyMsg(ctx, nc, msg)
if err != nil {
    // handle error
}
// gather responses

Configuration

Timeout and cancellation are handled by the context passed to RequestMany and RequestManyMsg. In addition, you can configure the following options:

• RequestManyStall: Sets the stall timer, useful in scatter-gather scenarios where subsequent responses are expected within a certain timeframe.
• RequestManyMaxMessages: Sets the maximum number of messages to receive.
• RequestManySentinel: Stops receiving messages once a sentinel message is received.