Design patterns are solutions to software design problems you find again and again in real-world application development. Patterns are about reusable designs and interactions of objects.
Creational design pattern
In software engineering, creational design patterns are design patterns that deal with object creation mechanisms, trying to create objects in a manner suitable to the situation. The basic form of object creation could result in design problems or in added complexity to the design. Creational design patterns solve this problem by somehow controlling this object creation.
Structural design pattern
In Software Engineering, Structural Design Patterns are Design Patterns that ease the design by identifying a simple way to realize relationships between entities.
Behavioural design pattern
In software engineering, behavioral design patterns are design patterns that identify common communication patterns between objects and realize these patterns. By doing so, these patterns increase flexibility in carrying out this communication.
Design patterns can help to solve a specific and commonly occurring problems that may be encountered when building applications that run in the cloud.
The design patterns are allocated to one or more of the following eight categories: availability, data management, design and implementation, messaging, management and monitoring, performance and scalibility, resiliency, and secuity.
Availability
Availability defines the proportion of time that the system is functional and working. It will be affected by system errors, infrastructure problems, malicious attacks, and system load. It is usually measured as a percentage of uptime. Cloud applications typically provide users with a service level agreement (SLA), which means that applications must be designed and implemented in a way that maximizes availability.
Data Management
Data management is the key element of cloud applications, and influences most of the quality attributes. Data is typically hosted in different locations and across multiple servers for reasons such as performance, scalability or availability, and this can present a range of challenges. For example, data consistency must be maintained, and data will typically need to be synchronized across different locations.
Design and Implementation
Good design encompasses factors such as consistency and coherence in component design and deployment, maintainability to simplify administration and development, and reusability to allow components and subsystems to be used in other applications and in other scenarios. Decisions made during the design and implementation phase have a huge impact on the quality and the total cost of ownership of cloud hosted applications and services.
Messaging
The distributed nature of cloud applications requires a messaging infrastructure that connects the components and services, ideally in a loosely coupled manner in order to maximize scalability. Asynchronous messaging is widely used, and provides many benefits, but also brings challenges such as the ordering of messages, poison message management, idempotency, and more.
Management and Monitoring
Cloud applications run in in a remote datacenter where you do not have full control of the infrastructure or, in some cases, the operating system. This can make management and monitoring more difficult than an on-premises deployment. Applications must expose runtime information that administrators and operators can use to manage and monitor the system, as well as supporting changing business requirements and customization without requiring the application to be stopped or redeployed.
Performance and Scalability
Performance is an indication of the responsiveness of a system to execute any action within a given time interval, while scalability is ability of a system either to handle increases in load without impact on performance or for the available resources to be readily increased. Cloud applications typically encounter variable workloads and peaks in activity. Predicting these, especially in a multi-tenant scenario, is almost impossible. Instead, applications should be able to scale out within limits to meet peaks in demand, and scale in when demand decreases. Scalability concerns not just compute instances, but other elements such as data storage, messaging infrastructure, and more.
Resiliency
Resiliency is the ability of a system to gracefully handle and recover from failures. The nature of cloud hosting, where applications are often multi-tenant, use shared platform services, compete for resources and bandwidth, communicate over the Internet, and run on commodity hardware means there is an increased likelihood that both transient and more permanent faults will arise. Detecting failures, and recovering quickly and efficiently, is necessary to maintain resiliency.
Security
Security is the capability of a system to prevent malicious or accidental actions outside of the designed usage, and to prevent disclosure or loss of information. Cloud applications are exposed on the Internet outside trusted on-premises boundaries, are often open to the public, and may serve untrusted users. Applications must be designed and deployed in a way that protects them from malicious attacks, restricts access to only approved users, and protects sensitive data.
A good API makes it easier to develop a program by providing all the building blocks, which are then put together by the programmer. APIs should expose only those module details that clients must know to use modules effectively
An API may be for a web-based system, operating system, or database system, and it provides facilities to develop applications for that system. Below is a list of client APIs:
Aerospike
Aerospike is a flash-optimized in-memory open source NoSQL database
RabbitMQ
RabbitMQ is an open source message broker software (sometimes called message-oriented middleware) that implements the Advanced Message Queuing Protocol (AMQP).
Owin
OWIN (Open Web Interface for .NET) is a standard for an interface between .NET web applications and web servers. OWIN aims to decouple the relationship between ASP.NET applications and IIS by defining a standard interface.
Restful API2
In computing, representational state transfer (REST) is the software architectural style of the World Wide Web. More precisely, REST is an architectural style consisting of a coordinated set of architectural constraints applied to components, connectors, and data elements, within a distributed hypermedia system.
MongoDb
MongoDB (from humongous) is a cross-platform document-oriented database. Classified as a NoSQL database, MongoDB eschews the traditional table-based relational database structure in favor of JSON-like documents with dynamic schemas (MongoDB calls the format BSON), making the integration of data in certain types of applications easier and faster.
SignalR
SignalR is a library for ASP.NET developers that simplifies the process of adding real-time web functionality to applications. Real-time web functionality is the ability to have server code push content to connected clients instantly as it becomes available, rather than having the server wait for a client to request new data.
Rest Hal
Hypertext Application Language (HAL) is an Internet Draft (a "work in progress") standard convention for defining hypermedia such as links to external resources within JSON or XML code. The standard was initially proposed on June 2012 specifically for use with JSON and has since become available in two variations, each specific to JSON or XML. The two associated MIME types are media type: application/hal+xml and media type: application/hal+json.
Rest HATEOAS
HATEOAS, an abbreviation for Hypermedia as the Engine of Application State, is a constraint of the REST application architecture that distinguishes it from most other network application architectures. The principle is that a client interacts with a network application entirely through hypermedia provided dynamically by application servers.
Managed Extensibility Framework (MEF)
Managed Extensibility Framework (MEF) is a component of .NET Framework 4.0 aiming to create lightweight, extensible applications. It aims to allow .NET application developers to discover and use extensions with no configuration required. It also aims to let extension developers encapsulate code easily and avoid fragile hard dependencies. Furthermore, it aims to allow extensions to be reused across applications. MEF was introduced as a part of .NET 4.0 and Silverlight 4.
Systems