202402131213
Status: #idea
Tags: DC

Communication Among Processes

• TODO Layers from slide 3 (2/13/24)

Higher Level Protocol & Middleware

• Domain Name System (DNS)
• Authentication protocol
• Distributed commit protocol
• Distributed locking protocol
• Remote Procedure Call (RPC)

Interface Definition Language

• IDL consists of a set of functions called by a client and implemented by server
• One can have compiled or interpreted language
  • Eg. client in Py, server in C
  • In such a case, include files have to be separate
• TODO image from slide 7 (2/13/24)
  TODO Class before 20th from arnav

ZeroMQ

• Socket may be bound to multiple addresses, allowing a server to handle messages from very different sources through a single interface

Design Patterns - ZeroMQ

• Request-reply
  • Request socket (REQ) is paired with reply socket (REP)
  • Ties the receipt of a message to the subsequent response
• Pub-sub
  • The server is PUB and the client is SUB
  • Only messages received through the SUB socket are the ones that the client has subscribed to
  • If multiple clients subscribe to the same messages, each client will get a copy of the same message
• Pipeline
  • A process producing tasks to be picked up by others
  • The first available worker will pick up work from the moduler
  • Pushing process does not really care which other process pulls in its requests

Role of Queue in Messaging

• Actually buffers which store these messages
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Flooding

• Undirected graph $G=<V,E>$
• Node $u$ forwards message $m$ to each enighbour $v$, provided u did not recive $m$ from $v$ in the first place
• How many messages?
  • Let $v_0$ initiate flooding of $m$, and let $\delta (v_0)$ be teh number of neighbours.
  • $$\delta (v_0)+\sum _{v\in v-v_0}\delta (v)-1=$$
  • Then total messages is $2|E|-|V|+1$
  • If G is a tree, then it is optimal at $|V|-1$. Othwewise <TODO Slide 23->26

References