DeliveryService
A library to allow transmitting and receiving messages within an asynchronous event loop.
Includes a receipt that all listeners for a given messgae have read it., (*1)
This library primarily holds the interfaces designed to provide the discussed functionality
and generic implementations that are not dependent on any particular event reactor. For
functional implementations of these interfaces please check out:, (*2)
This library requires PHP7! Because of this it will not be production ready until PHP7 is., (*3)
Overview
Here we talk about the interfaces that provide the messaging abstraction layer we place on
top of your favorite reactor. It is assumed from this point forward that you have a high-level
understanding of event loops, promises, and promisors., (*4)
Message
Represents a type and a set of data that can be transmitted and received. In other words, a message.
The payload of the message can be whatever is appropriate for your domain., (*5)
<?php
namespace Cspray\DeliveryService;
interface Message {
public function getType() : string;
public function getPayload();
}
Receipt
Every time you send a message you get a Receipt. This is a promise that will invoke any callbacks
when the Message has been received by everybody that's supposed to receive it. The callback will
be invoked regardless of whether listeners threw an exception; check out the DeliveryResults interface
for more information., (*6)
<?php
namespace Cspray\DeliveryService;
interface Receipt {
/**
* The $callback should match the below signature:
*
* function(DeliveryResults $results, Message $message) {
*
* }
*/
public function delivered(callable $callback);
}
DeliveryResults
Represents the results of a Message having been delivered to all of its recipients.
An implementation of this interface gets passed to all callbacks attached to a
Receipt., (*7)
<?php
namespace Cspray\DeliveryService;
interface DeliveryResults {
public function getNumberListeners() : int;
public function getSuccessfulResults() : array;
public function getFailureResults() : array;
// The arrays returned from both successful and failed should match the following format
// [$listenerId => $listenerReturnOrThrownException]
}}
Receiver
Your code needs some way to receive messages; you accomplish this by adding a listener
for a specific type of Message to a Receiver., (*8)
<?php
namespace Cspray\DeliveryService;
interface Receiver {
// The string returned should be a unique identifier for the specific type and callable passed
public function listen(string $messageType, callable $callback) : string;
public function removeListener(string $listenerId);
public function getListenersForType(string $messageType);
}
Transmitter
If you expect to receive a message you need to send one first! The Transmitter interface is designed
to do exactly that. Specifically we expect implementations to add Messages to a MessageQueue implementation,
we'll get to that one below., (*9)
<?php
namespace Cspray\DeliveryService;
interface Transmitter {
public function send(Message $message) : Receipt;
public function getMessageQueue() : MesageQueue;
}
MessageQueue
A first-in, first-out queue that holds Messages that are awaiting delivery. When a message is delivered it is
removed from the queue., (*10)
<?php
namespace Cspray\DeliveryService;
interface MessageQueue {
public function enqueue(MessageReceiptPromisor $messageReceiptPromisor);
public function dequeue() : MessageReceiptPromisor;
public function isEmpty() : bool;
public function hasMessages() : bool;
}
Finally the interface that brings everything together. It coordinates with the event reactor of your
choice, as well as a transmitter and receiver to actually dispatch thes Messages., (*11)
<?php
namespace Cspray\DeliveryService;
interface Mediator {
public function startSendingMessages();
public function stopSendingMessages();
}
For more information check out the implementation libraries that are listed above., (*12)
Wallogit.com
