Message pattern

Message scope

Inter-process and inner-process

event-driven model章节的侧重点是inter-process；

wikipedia Messaging pattern

In software architecture, a messaging pattern is a network-oriented architectural pattern which describes how two different parts of a message passing system connect and communicate with each other.

NOTE :

上面这段话对message的定义是局限于network的，其实我觉得我们需要从更加宽泛的角度来认识message，而不是局限在network；

在我们的programming中，其实很多时候都涉及到了通过message来通知，传递，有的时候，它们并不是network间，可能就是在process内（如condition variable（参见youdao notebook的《cppreference-std-condition_variable.md》），或者message queue）；所以对message的认知要拓宽；在youdao notebook的《event-and-message-passing-summary.md》中对message进行了综述；其实本文则从另外一个角度来进行阐述：message的pattern；的确，仅仅认知message是完全不能够将其应用起来解决实际问题的，还需要根据问题采取合适的架构，这就涉及message pattern了；所以认知到messaging pattern对于理解一些应用是非常重要的；

In telecommunications, a message exchange pattern (MEP) describes the pattern of messages required by a communications protocol to establish or use a communication channel. There are two major message exchange patterns — a request–response pattern, and a one-way（单程的） pattern. For example, HTTP is a request–response pattern protocol, and UDP is a one-way pattern.[1]

NOTE: 本文所描述的messaging pattern是建立在network protocol的基础上而构建的更加高级的功能，需要将它和比较底层的network protocol区分开来；

ØMQ

The ØMQ message queueing library provides so-called sockets (a kind of generalization over the traditional IP and Unix sockets) which require indicating a messaging pattern to be used, and are optimized for each pattern. The basic ØMQ patterns are:[4]

1、Request–reply connects a set of clients to a set of services. This is a remote procedure call and task distribution pattern.[clarification needed]

2、Publish–subscribe connects a set of publishers to a set of subscribers. This is a data distribution pattern.[clarification needed]

3、Push–pull connects nodes in a fan-out / fan-in pattern that can have multiple steps, and loops. This is a parallel task distribution and collection pattern.[clarification needed]

NOTE: 并没有搞懂

4、Exclusive pair connects two sockets in an exclusive pair. This is a low-level pattern for specific, advanced use cases.

NOTE: 并没有搞懂

Each pattern defines a particular network topology. Request-reply defines so-called "service bus", publish-subscribe defines "data distribution tree", push-pull defines "parallelised pipeline". All the patterns are deliberately designed in such a way as to be infinitely scalable and thus usable on Internet scale.[5]

NOTE: 最后一段话非常好；