NatsBareMessageQueue

Extends: NatsAbstractMessageQueue

Description

The NatsBareMessageQueue class allows you to create message queues that send and receive messages via a NATS message broker.

Configuration parameters

• subject: name of NATS topic (subject) to subscribe
• queue_group: name of NATS queue group
• connection(s):
  • discovery_key: (optional) key to retrieve the connection from IDiscovery
  • host: host name or IP address
  • port: port number
  • uri: resource URI or connection string with all parameters in it
• credential(s):
  • store_key: (optional) key to retrieve the credentials from ICredentialStore
  • username: username
  • password: user’s password
• options:
  • serialize_message: (optional) true to serialize the entire message as JSON, false to only send the message payload (default: true)
  • retry_connect: (optional) turns on/off automated reconnect when the connection is lost (default: true)
  • max_reconnect: (optional) maximum number of reconnection attempts (default: 3)
  • reconnect_timeout: (optional) number of milliseconds to wait on each reconnection attempt (default: 3000)
  • flush_timeout: (optional) number of milliseconds to wait on flushing messages (default: 3000)

References

• *:logger:*:*:1.0 - (optional) ILogger components to pass log messages
• *:counters:*:*:1.0 - (optional) ICounters components to pass collected measurements
• *:discovery:*:*:1.0 - (optional) IDiscovery services
• *:credential-store:*:*:1.0 - (optional) ICredentialStore to resolve credentials
• *:connection:nats:*:1.0 - (optional) Shared connection to NATS service

Constructors

NewNatsBareMessageQueue

Creates a new instance of the message queue.

NewNatsBareMessageQueue(name string) *NatsBareMessageQueue

• name: string - (optional) queue name.

Methods

EndListen

Ends listening for incoming messages. When this method is called, Listen unblocks the thread and execution continues.

(c [*NatsBareMessageQueue[T]]) EndListen(ctx context.Context, context IContext)

• ctx: context.Context - operation context.
• context: IContext - (optional) a context to trace execution through a call chain.

Listen

Listens for incoming messages and blocks the current thread until the queue is closed.

See IMessageReceiver

(c [*NatsBareMessageQueue[T]]) Listen(ctx context.Context, context IContext, receiver IMessageReceiver) error

• ctx: context.Context - operation context.
• context: IContext - (optional) a context to trace execution through a call chain.
• receiver: IMessageReceiver - receiver used to receive incoming messages.
• returns: error - error or nil if no errors occurred.

Peek

Peeks a single incoming message from the queue without removing it. If there are no messages available in the queue, it returns nil.

(c [*NatsBareMessageQueue[T]]) Peek(ctx context.Context, context IContext) (*MessageEnvelope, error)

• ctx: context.Context - operation context.
• context: IContext - (optional) a context to trace execution through a call chain.
• returns: (*MessageEnvelope, error) - peeked message.

PeekBatch

Peeks multiple incoming messages from the queue without removing them. If there are no messages available in the queue, it returns an empty list.

• Important: This method is not supported by NATS.

(c [*NatsBareMessageQueue[T]]) PeekBatch(ctx context.Context, context IContext, messageCount int64) ([]*MessageEnvelope, error)

• ctx: context.Context - operation context.
• context: IContext - (optional) a context to trace execution through a call chain.
• messageCount: int64 - maximum number of messages to peek.
• returns: ([]*MessageEnvelope, error) - list with peeked messages.

Receive

Receives an incoming message and removes it from the queue.

(c [*NatsBareMessageQueue[T]]) Receive(ctx context.Context, context IContext, waitTimeout time.Duration) (*MessageEnvelope, error)

• ctx: context.Context - operation context.
• context: IContext - (optional) a context to trace execution through a call chain.
• waitTimeout: time.Duration - timeout in milliseconds to wait for a message to come.
• returns: (*MessageEnvelope, error) - received message or nil if nothing was received.

Examples

ctx := context.Background()
queue := NewNatsBareMessageQueue("myqueue")
queue.Configure(ctx, cconf.NewConfigParamsFromTuples(
	"subject", "mytopic",
	"queue_group", "mygroup",
	"connection.protocol", "nats"
	"connection.host", "localhost"
	"connection.port", 1883,
))

_ = queue.Open(ctx, "123")

_ = queue.Send(ctx, "123", NewMessageEnvelope("", "mymessage", "ABC"))

message, err := queue.Receive(ctx, "123", 10000*time.Milliseconds)
if (message != nil) {
	...
	queue.Complete(ctx, message);
}

See also

• MessageQueue

• MessagingCapabilities