Introduction to Reactive Systems

Question 1

Reactive is

Answer 1

A set of Design Principles

Message Driven
Resilient
Elastic
Responsive

Question 2

What’s the primary goal of Reactive Architecture?

Answer 2

• Software that maintains a Consistent Level of Quality and Responsiveness (No downtime and good response times).
• Failures with little to no effect on the user.
• Software that can be distributed across many machines.
• Software that scale consuming only the necessary resources.

Question 3

When people talk about Reactive, they generally mean …

Answer 3

• Reactive System (architecture and design)
• Reactive Programming (declarative event-based)
• Functional Reactive Programming (FRP)

Question 4

Message Driven is the foundation for …

Answer 4

Elastic, Resilient and Responsive systems

Message: Asynchronous and Non-blocking

Non-Blocking: don’t wait for a response, to avoid consuming resources.

Question 5

Message Driven provides …

Answer 5

Loose Coupling.
Isolation.
Location Transparency.

An Asynchronous Boundary.

Question 6

Elastic

Answer 6

A Reactive System remains Responsive, despite changes in System Load.

Question 7

Resilient

Answer 7

A Reactive System remains Responsive, even when failures occur.

Question 8

The Main Keys for a Resilient System ..

Answer 8

Containment (a consequence of Isolation)
failures are isolated into a single component (they don’t propagate and bring down the whole system).

Isolation: Services can function on their own, they don’t have external dependencies.

Delegation: Recovery is managed by an external component because the failing component is not reliable, if the system goes down the system can’t restart itself because it’s down.

Replication: Multiple copies of a service.

Question 9

Responsive is …

Answer 9

Cornerstone of Usability.

it is the consequence of a Resilient, Elastic and Message Driven System

Question 10

It is not a Reactive System if …

Answer 10

• if it is deploy in single node.

- if there is a local cache and there is not way to sync with multiple nodes, hard to scale up, consistency problem.

Question 11

Reactive Programming is …

Answer 11

Is a Subset Of Asynchronous Programming and a Paradigm where the availability of new Information drives the logic forward rather than having control flow driven by a Thread-of-execution

Question 12

Reactive Programming Techniques

Answer 12

Takes a problem and breaks it up into small discrete steps, those are executed in an Asynchronous Non-blocking fashion (some sort of callback mechanism).

Futures, Reactive Stream, RxJava, RxScala.

Question 13

Actor Model Concepts:

Answer 13

• All computations occur inside of an actor, the Principle Abstraction is Encapsulating all computation inside of an actor.
• Actors communicate only through Asynchronous Messages Location transparency
• Each actor is addressable, it has a unique address

Question 14

Location transparency:

Answer 14

• Local calls look like remote calls, assumes you are always making remote call and you have to assume remote failure scenarios (Eg. network failures)
• You can’t assume that the message is delivered.

Question 15

Transparent Remoting:

Answer 15

Remote calls look like local calls, hides the fact that you are making remote calls and also potential failure scenarios (Eg. network failues)