2.1 Architectural Styles
The architecture of a distributed system refers to the overall design and structure of the system, including the hardware, software, and communication protocols used. The choice of architectural style can have a significant impact on the performance, reliability, and scalability of the system.
There are several different architectural styles that can be used in distributed systems, including:
Client-server architecture: in this style, clients request services from servers. This is a common architecture for distributed systems, as it allows clients to access services and resources without having to handle the underlying complexity.
Peer-to-peer architecture: in this style, each node is both a client and a server. This allows for decentralized communication and decision-making, but it can also lead to scalability and performance issues.
Microservices architecture: in this style, the system is divided into small, independent components that communicate with each other through APIs. This allows for flexible and scalable development, but it can also increase the complexity of the system.
2.2 Middleware organization
Middleware is a layer of software that sits between the hardware and the application software in a distributed system. It is responsible for managing communication between different parts of the system and providing services such as security, data management, and integration with other systems.
There are several different types of middleware, including:
Operating system-level middleware: this type of middleware is integrated into the operating system and provides services such as file management and networking.
Database middleware: this type of middleware provides connectivity between databases and applications. It allows for the integration of different types of databases and enables the use of SQL to access data stored in non-relational databases.
Application server middleware: this type of middleware provides services such as connection pooling and load balancing to application servers. It can improve the performance and scalability of applications by distributing the workload across multiple servers.
2.3 System Architecture
The system architecture of a distributed system is the overall design of the system and how it is organized. It includes the hardware, software, and communication protocols used to connect the various components of the system.
The architecture of a distributed system can be based on a single central server or a distributed network of servers. A central server architecture is simpler to design and manage, but it can be less scalable and less resilient to failures. A distributed network architecture is more complex but offers greater scalability and resilience.
The architecture of a distributed system should be designed to support the needs of the system, including performance, reliability, and security. It should also be flexible enough to accommodate changes in the system over time, such as the addition of new components or the expansion of the network.
2.4 Example Architectures
Some examples of distributed system architectures include:
The three-tier architecture: in this architecture, the system is divided into three layers: the presentation layer, the application logic layer, and the data storage layer. The presentation layer is responsible for interacting with the user, the application logic layer contains the business logic of the system, and the data storage layer manages the storage and retrieval of data.
The microservices architecture: in this architecture, the system is divided into small, independent components that communicate with each other through APIs. This allows for flexible and scalable development, but it can also increase the complexity of the system.
The cloud computing architecture: in this architecture, users access services and resources over the internet. Cloud computing allows for on-demand access to computing resources and can improve scalability and reduce the need for hardware and software infrastructure