[Distributed systems] Communication model

types of process communication
1. same machine, same process (inter thread)
2. same machine (inter process)
3. over network (remote machines)

process
1. heterogeneous (all can be different)
2. expensive communication cost (limited ... number and size !!!)

>> communication models and protocols are needed

communication model components = message format +protocol

RPC
= remote procedure call

remote procedures are called like normal local procedures
= tight coupling between processes

implements the protocol
rpc framework uses the interface to automatically generate two proxies
1. stub = client side proxy = serialize = raw msg -> rpc msg
2. skeleton = server side proxy = deserialize = rpc msg -> raw msg

MSA = micro servie architecture

rpc protocols propose blocking communication, but it is easy to turn the idea into non-blocking communication

- abstraction
- good performance
- extensive
- appear like local calls

- tight coupling of server and client code
- local and remote function calls are different, so remote function calls are unpredictable