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Microservices on AWS
AWS Whitepaper

Simple Microservices Architecture on AWS

In the past, typical monolithic applications were built using different layers, for example, a user interface (UI) layer, a business layer, and a persistence layer. A central idea of a microservices architecture is to split functionalities into cohesive “verticals”—not by technological layers, but by implementing a specific domain. The following figure depicts a reference architecture for a typical microservices application on AWS.

User Interface

Modern web applications often use JavaScript frameworks to implement a single-page application that communicates with a RESTful API. Static web content can be served using Amazon Simple Storage Service (Amazon S3) and Amazon CloudFront.

Note

CloudFront is a global content delivery network (CDN) service that accelerates delivery of your websites, APIs, video content, and other web assets.

Since clients of a microservice are served from the closest edge location and get responses either from a cache or a proxy server with optimized connections to the origin, latencies can be significantly reduced. However, microservices running close to each other don’t benefit from a CDN. In some cases, this approach might even add more latency. It is a best practice to implement other caching mechanisms to reduce chattiness and minimize latencies.

Microservices

The API of a microservice is the central entry point for all client requests. The application logic hides behind a set of programmatic interfaces, typically a RESTful web services API. This API accepts and processes calls from clients and might implement functionality such as traffic management, request filtering, routing, caching, and authentication and authorization.

Many AWS customers use the Elastic Load Balancing (ELB) Application Load Balancer together with Amazon EC2 Container Service (Amazon ECS) and Auto Scaling to implement a microservices application. The Application Load Balancer routes traffic based on advanced application-level information that includes the content of the request.

Note

ELB automatically distributes incoming application traffic across multiple Amazon EC2 instances.

The Application Load Balancer distributes incoming requests to Amazon ECS container instances running the API and the business logic.

Note

Amazon EC2 is a web service that provides secure, resizable compute capacity in the cloud. It is designed to make web-scale cloud computing easier for developers.

Amazon EC2 Container Service (Amazon ECS) is a highly scalable, high performance container management service that supports Docker containers and allows you to easily run applications on a managed cluster of Amazon EC2 instances.

Amazon ECS container instances are scaled out and scaled in, depending on the load or the number of incoming requests. Elastic scaling allows the system to be run in a cost-efficient way and also helps protect against denial of service attacks.

Note

Auto Scaling helps you maintain application availability and allows you to scale your Amazon EC2 capacity up or down automatically according to conditions you define.

Containers

A common approach to reducing operational efforts for deployment is container-based deployment. Container technologies like Docker have increased in popularity in the last few years due to the following benefits:

  • Portability – Container images are consistent and immutable, that is, they behave the same no matter where they are run (on a developer’s desktop as well as in a production environment).

  • Productivity – Containers increase developer productivity by removing cross-service dependencies and conflicts. Each application component can be broken into different containers running a different microservice.

  • Efficiency – Containers allow the explicit specification of resource requirements (CPU, RAM), which makes it easy to distribute containers across underlying hosts and significantly improve resource usage. Containers also have only a light performance overhead compared to virtualized servers and efficiently share resources on the underlying operating system.

  • Control – Containers automatically version your application code and its dependencies. Docker container images and Amazon ECS task definitions allow you to easily maintain and track versions of a container, inspect differences between versions, and roll back to previous versions.

Amazon ECS eliminates the need to install, operate, and scale your own cluster management infrastructure. With simple API calls, you can launch and stop Docker-enabled applications, query the complete state of your cluster, and access many familiar features like security groups, load balancers, Amazon Elastic Block Store (Amazon EBS) volumes, and AWS Identity and Access Management (IAM) roles.

After a cluster of EC2 instances is up and running, you can define task definitions and services that specify which Docker container images to run on the cluster. Container images are stored in and pulled from container registries, which may exist within or outside your AWS infrastructure. To define how your applications run on Amazon ECS, you create a task definition in JSON format. This task definition defines parameters for which container image to run, CPU, memory needed to run the image, how many containers to run, and strategies for container placement within the cluster. Other parameters include security, networking, and logging for your containers.

Amazon ECS supports container placement strategies and constraints to customize how Amazon ECS places and terminates tasks. A task placement constraint is a rule that is considered during task placement. You can associate attributes, essentially key/value pairs, to your container instances and then use a constraint to place tasks based on these attributes. For example, you can use constraints to place certain microservices based on instance type or instance capability, such as GPU-powered instances.

Docker images used in Amazon ECS can be stored in Amazon EC2 Container Registry (Amazon ECR). Amazon ECR eliminates the need to operate and scale the infrastructure required to power your container registry.

Note

Amazon EC2 Container Registry (Amazon ECR) is a fully-managed Docker container registry that makes it easy for developers to store, manage, and deploy Docker container images. Amazon ECR is integrated with Amazon EC2 Container Service (Amazon ECS), simplifying your development to production workflow.

Data Store

The data store is used to persist data needed by the microservices. Popular stores for session data are in-memory caches such as Memcached or Redis. AWS offers both technologies as part of the managed Amazon ElastiCache service.

Note

Amazon ElastiCache is a web service that makes it easy to deploy, operate, and scale an in-memory data store or cache in the cloud. The service improves the performance of web applications by allowing you to retrieve information from fast, managed, in-memory caches, instead of relying entirely on slower disk-based databases.

Putting a cache between application servers and a database is a common mechanism to alleviate read load from the database, which, in turn, may allow resources to be used to support more writes. Caches can also improve latency.

Relational databases are still very popular for storing structured data and business objects. AWS offers six database engines (Microsoft SQL Server, Oracle, MySQL, MariaDB, PostgreSQL, and Amazon Aurora) as managed services via Amazon Relational Database Service (Amazon RDS).

Note

Amazon RDS makes it easy to set up, operate, and scale a relational database in the cloud. It provides cost-efficient and resizable capacity while managing time-consuming database administration tasks, freeing you to focus on applications and business.

Relational databases, however, are not designed for endless scale, which can make it very hard and time-intensive to apply techniques to support a high number of queries.

NoSQL databases have been designed to favor scalability, performance, and availability over the consistency of relational databases. One important element is that NoSQL databases typically do not enforce a strict schema. Data is distributed over partitions that can be scaled horizontally and is retrieved via partition keys.

Since individual microservices are designed to do one thing well, they typically have a simplified data model that might be well suited to NoSQL persistence. It is important to understand that NoSQL-databases have different access patterns than relational databases. For example, it is not possible to join tables. If this is necessary, the logic has to be implemented in the application.

Note

Amazon DynamoDB is a fast and flexible NoSQL database service for all applications that need consistent, single-digit millisecond latency at any scale.

You can use Amazon DynamoDB to create a database table that can store and retrieve any amount of data and serve any level of request traffic. DynamoDB automatically spreads the data and traffic for the table over a sufficient number of servers to handle the request capacity specified by the customer and the amount of data stored, while maintaining consistent and fast performance.

DynamoDB is designed for scale and performance. In most cases, DynamoDB response times can be measured in single-digit milliseconds. However, there are certain use cases that require response times in microseconds. For these use cases, DynamoDB Accelerator (DAX) provides caching capabilities for accessing eventually consistent data. DAX does all the heavy lifting required to add in- memory acceleration to your DynamoDB tables, without requiring developers to manage cache invalidation, data population, or cluster management.

DynamoDB provides an auto scaling feature to dynamically adjust provisioned throughput capacity on your behalf, in response to actual traffic patterns.

Provisioned throughput is the maximum amount of capacity that an application can consume from a table or index. When the workload decreases, Application

Auto Scaling decreases the throughput so that you don't pay for unused provisioned capacity.