io.atomix.group.messaging

Interface Message<T>

public interface Message<T>

Represents a reliable message received by a member to be processed and acknowledged.

Messages are sent by DistributedGroup users to any member of a group. Messages are replicated and persisted within the Atomix cluster before being pushed to clients on a queue. Once a message is received by a message listener, the message may be processed asynchronously and either acknowledged or failed once processing is complete.

   
   DistributedGroup group = atomix.getGroup("message-group").get();
   group.join().thenAccept(member -> {
     MessageConsumer<String> consumer = member.messaging().consumer("foo");
     consumer.onMessage(message -> {
       processTask(message).thenRun(() -> {
         message.ack();
       });
     });
   });
   
 

Consumers may also send replies to messages. To send a reply, use the reply(Object) method. Note that replies may or may not be received by producers depending on their configuration. Producers must specify support for the REQUEST_REPLY execution policy to receive replies.

   
   consumer.onMessage(message -> {
     message.reply("Hello world!");
   });
   
 

Author:

Method Summary

Modifier and Type	Method and Description
CompletableFuture<Void>	ack() Acknowledges completion of the message.
CompletableFuture<Void>	fail() Fails processing of the message.
long	id() Returns the message ID.
T	message() Returns the message value.
CompletableFuture<Void>	reply(Object message) Replies to the message.

Method Detail

id

long id()

Returns the message ID.

The message ID is guaranteed to be unique and monotonically increasing within a given message queue. Tasks received across members are not associated with one another.

Returns:

The monotonically increasing message ID.

message

T message()

Returns the message value.

This is the value that was submitted by the sending process.

Returns:

The message value.

reply

CompletableFuture<Void> reply(Object message)

Replies to the message.

Replies are sent through the Atomix cluster as a write operation. Users can await the completion of the underlying write operation through the returned CompletableFuture.

Parameters:

message - The reply message.

Returns:

A completable future to be completed once the reply has been sent.

ack

CompletableFuture<Void> ack()

Acknowledges completion of the message.

Once a message is acknowledged, an ack will be sent back to the process that submitted the message. Acknowledging completion of a message does not guarantee that the sender will learn of the acknowledgement. The acknowledgement itself may fail to reach the cluster or the sender may crash before the acknowledgement can be received. Acks serve only as positive acknowledgement, but the lack of an ack does not indicate failure.

Returns:

A completable future to be completed once the message has been acknowledged.

fail

CompletableFuture<Void> fail()

Fails processing of the message.

Once a message is failed, a failure message will be sent back to the process that submitted the message for processing. Failing a message does not guarantee that the sender will learn of the failure. The process that submitted the message may itself fail.

Returns:

A completable future to be completed once the message has been failed.