5 - Pub Sub

Question 1

Advantages of client server

Answer 1

Easy
Thin clients

Question 2

Drawbacks of client server

Answer 2

Interaction one to one
Each entitty must know how to address partner
Both must be available
Inherently synchronous
Only pull based

Question 3

Pub Sub

Answer 3

Distributed Event based systems
Stores subscriptions and correctly delivers event notifs

Question 4

Publishers (producers)

Answer 4

publish structured events to a service

Question 5

Subscribers (consumers)

Answer 5

Register interest in particular events through subscriptions

Question 6

Examples of Pub Sub

Answer 6

Live data broadcasting
Monitoring
Cooperation
Ubiquitous Computing

Question 7

Characteristics of Pub/Sub system

Answer 7

Heterogeneous (distinct components can be made to work together)
Asynchronous

Question 8

Space coupled

Answer 8

Comms directed to receiver

Question 9

Space uncoupled

Answer 9

Sender does not need to know receiver identity

Question 10

Time coupled

Answer 10

Receiver must exit at that time

Question 11

Time uncoupled

Answer 11

Sender and receiver can have independent lifetimes

Question 12

Channel based subscriptions

Answer 12

Subscribe to entire channel
Simple
No interplay between channels

Question 13

Topic based subscriptions

(think about how the topics are laid out)

Answer 13

Topics organised hierarchically in subtree

Subscribing means receiving all messages to this node and below

Question 14

Content based subscriptions

Answer 14

Subscribers define predicates (constraints) on attribute values of events

Question 15

Event Schema

Answer 15

Un-typed set of typed attributes.

<attr-name, attr-type, attr-value>

Question 16

Subscription Schema

Answer 16

A set of triplets of the form
<attr-name,attr-type,attr-value-predicate>

Specifies values of interest

Question 17

Centralised model

Answer 17

Central server acts as event broker

Question 18

Event matching steps

Answer 18

Subscription processing (index and store them)
Event processing (identify matched subscriptions)
Event delivery (to clients)

Question 19

Distributed Model

Answer 19

Sys of network of brokers.

Each local broker has its own matching engine

Question 20

Serverless - what is it and when is it used?

Answer 20

cloud native platform

short running, stateless computations
event-driven apps
scale up and down
charged by use

Question 21

When are cloud functions triggered

Answer 21

By events

Question 22

Stateful vs Stateless

Answer 22

Apps that track state vs do NOT

Question 23

Why must states be kept separate to cloud functions?

Answer 23

Function instances are destroyed after use

Question 24

Advantages of serverless

Answer 24

Cheaper (at low use)
Scalable
More time devoted to user experience

Question 25

Disadvantages of serverless

Answer 25

Vendor lockin
Staff retraining to rearchitect apps

Question 26

In large data scenarios, why might system and network delays affect real time alerts?

Answer 26

Lack of bandwitch, large data latency. Cannot reach aggregation point in time.
Lack of scalability for processing large data