1.11 Distributed-System Communication

1. What Is Distributed-System Communication?

• After a monolithic system is split into multiple subsystems, the subsystems need to communicate to provide a complete service.

2. Communication Methods Between Distributed Systems

2.1. Synchronous Communication

• A calls B and waits for the result to return.

2.1.1. REST vs RPC

• Restful.md (the related note has not yet been published).
• How to Design an RPC Framework

	RPC	REST
Idea	Object-oriented	Resource-oriented
Communication protocol	TCP	HTTP
Message protocol	Binary	JSON
Performance	High	Low
IDL	proto. See below	swagger. See below
Client	Strongly typed	Weakly typed

• API definitions between the service and client.

Operation	RPC	REST
Register	POST /signup	POST /persons
Deregister	POST /resign { “personid”: “1234” }	DELETE /persons/1234
Read user information	GET /readPerson?personid=1234	GET /persons/1234
Read user’s item list	GET /readUsersItemsList?personid=1234	GET /persons/1234/items
Add an item to user’s item list	POST /addItemToUsersItemsList { “personid”: “1234”; “itemid”: “456” }	POST /persons/1234/items { “itemid”: “456” }
Update an item	POST /modifyItem { “itemid”: “456”; “key”: “value” }	PUT /items/456 { “key”: “value” }
Delete an item	POST /removeItem { “itemid”: “456” }	DELETE /items/456

• API version: MAJOR.MINOR.PATCH
  • MAJOR: API is not backward compatible.
  • MINIOR: backward-compatible API feature enhancement.
  • PATCH: backward-compatible API bug fix.

2.2. Asynchronous Communication

• A calls B and returns directly without waiting for the result.
• How to Design an Asynchronous System.md (the related note has not yet been published).

2.3. Synchronous Communication vs Asynchronous Communication

• I/O Models.md (the related note has not yet been published).

	Synchronous	Asynchronous
Can the result be obtained in real time?	Yes	No
Throughput	Low	High

3. Message Formats for Communication Between Distributed Systems

• The physical model in Data Models.

3.1. Text

3.2. Binary