Chapter 2 - Distriputed Systems Architecture Basics

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Questions and Answers

What is the primary role of a producer service in a queueing system?

To process the messages

To write messages to the queue (correct)

To retrieve messages from the queue

To delete messages from the database

Queueing technologies can provide synchronous communications.

False (B)

What does Amdahl's law help to calculate?

The theoretical acceleration of code when adding more CPU cores.

When an application uses queueing, data is expected to be persisted __________.

eventually Signup and view all the answers

Match the following terms with their correct descriptions:

Producer = Writes messages to the queue Consumer = Removes messages from the queue Asynchronous communication = Transmission that allows for non-blocking processes Scalability = The ability to handle increased load gracefully Signup and view all the answers

Which of the following factors can limit the effectiveness of scalability, regardless of the architecture?

Insufficient hardware resources (C) Signup and view all the answers

Increasing the number of CPU cores will always improve the scalability of a single-threaded application.

False (B) Signup and view all the answers

What is meant by the term 'eventual persistence' in the context of queueing systems?

Data will be persisted after some delay, allowing for improved responsiveness. Signup and view all the answers

What does 'scaling up' typically involve in application service architecture?

Upgrading to a larger server instance (C) Signup and view all the answers

Scaling out is also known as horizontal scaling.

True (A) Signup and view all the answers

List one advantage of scaling out an application.

Increased application capacity Signup and view all the answers

Scaling up usually costs more for __________.

hardware Signup and view all the answers

Which of the following is NOT a fundamental element required to successfully scale out an application?

High session state management (C) Signup and view all the answers

Match the following terms with their descriptions:

Scaling Up = Upgrading hardware resources Scaling Out = Replicating services across multiple nodes Stateless Services = Services that do not manage session states Latency = Time delay in processing requests Signup and view all the answers

If one of the services in a scaled-out architecture fails, the application will not be able to reissue the lost requests.

False (B) Signup and view all the answers

What happens to the request load when scaling out by adding N replicas?

The request load is distributed among the replicas. Signup and view all the answers

What is the primary reason why multithreaded code is essential for scalability?

It allows tasks to run independently. (B) Signup and view all the answers

Upgrading hardware always results in improved performance and scalability.

False (B) Signup and view all the answers

What test does the Java service perform in the benchmark system?

The service accepts requests, queries a database, and returns results to the client. Signup and view all the answers

Efficient multithreaded programming is necessary for achieving __________ in distributed systems.

scalability Signup and view all the answers

Match the following terms with their descriptions:

Amdahl's Law = Demonstrates the limits of parallel processing Throughput = The rate at which requests are processed AWS EC2 = A cloud computing service provided by Amazon Multithreading = Running multiple threads in parallel for efficiency Signup and view all the answers

Which statement reflects a common misconception about hardware upgrades?

Adding hardware guarantees improved performance. (A) Signup and view all the answers

What is essential to assess the effects of hardware upgrades?

Running experiments and taking measurements. Signup and view all the answers

The client, service, and database in the benchmark test run on different hardware resources.

True (A) Signup and view all the answers

Study Notes

Increasing Responsiveness with Queueing

Asynchronous communication is used to improve responsiveness by providing temporary storage for write operations.
Producer service writes to the queue while a consumer service removes messages and updates the database.
Queueing technologies provide a solution for situations where the outcome of a write operation isn't immediately needed.

Systems and Hardware Scalability

Software architecture and code can be limited by inadequate hardware.
The open-source and commercial platforms used in scalable systems are designed to use resources like CPU cores, memory, and disks.
Scaling up is simple and involves increasing the hardware resources, which increases costs.
Amdahl's Law states that adding more CPU cores won't improve performance if the code is single-threaded or has many serialized sections.
Scaling out is a strategy that uses multiple copies of a service running on different server nodes to handle increased request loads.

Scaling Out

Scaling out distributes requests evenly across service replicas, theoretically improving capacity and scalability.
Scaling out requires:
- Stateless services: Ensures no code changes are required when adding new instances.
- Load balancing: Distributes incoming requests among multiple servers to prevent overloading a single server.
Resilience to failures is a key benefit of scaling out, as requests can be reissued to other service instances if one instance fails.
Amdahl's Law highlights the importance of multithreaded code for optimal scalability.
Figure 2-8 demonstrates the impact of upgrading database hardware on throughput.

Scaling Up vs. Scaling Out

Scaling up can be less effective if code is not optimized for multithreading.
Scaling out is generally a more cost-effective approach than scaling up, as it allows for more gradual resource allocation.
Experimentation and analysis are essential for understanding the impact of hardware upgrades on performance and making informed decisions.

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Description

This quiz covers key concepts in increasing responsiveness through queueing and the principles of systems and hardware scalability. Explore how asynchronous communication and scaling strategies impact performance and resource utilization in software architecture.