The essential guide to Microservices Design Patterns

What is Microservices architecture and how does it work?

At its core, microservices architecture is a design approach for developing software applications as a collection of small, independent services. Each service is focused on a specific business capability and can be created, deployed, and scaled independently from other services in the application.

Consequently, each service typically has its own database and communicates with other services through lightweight APIs. Developers can build and deploy each service independently, using the programming language and technology stack best suited to its needs.

Microservices Design Patterns

However, developing, deploying, and managing such a microservices architecture poses its own share of challenges. For instance, managing shared access, ensuring data consistency, maintaining the security of service, facilitating communication between services, and managing dependencies. To address these challenges, microservices design patterns use architectural patterns that provide efficient administration of these services, overcome challenges, and maximize performance. By choosing the right design pattern for your use case, you can increase component reusability and reduce development time and effort. Over time, this can eliminate the need to reinvent the wheel each time you make changes to your application.

Commonly referenced Microservices Design Patterns:

1. API Gateway
   As a microservices-based application grows in complexity, the number of endpoints can become unwieldy, making it difficult to manage and maintain. An API gateway acts as a single entry point to the application, abstracting away the complexity of the underlying microservices. This approach simplifies the communication between the client and the microservices, as clients no longer need to know the specific location or address of each individual microservice. Instead, clients can interact with a single endpoint provided by the API gateway, which then handles the complexity of communicating with the underlying microservices.
   API gateways also provide other important functions, such as authentication, rate limiting, request/response transformation, and service discovery. These features can help improve the security, scalability, and reliability of a microservices architecture.
   Another benefit of using an API gateway is that it can simplify the management and monitoring of a microservices architecture. By centralizing the routing and communication between services, an API gateway can provide a single point of control for managing traffic and monitoring service performance.
2. Access tokens
   Access tokens are commonly used as a security mechanism in microservice architecture to authorize and authenticate requests between services. Here's how it typically works:
   1. A client sends a request to a service.
   2. The service receiving the request verifies the identity of the client by checking the access token that was included with the request.
   3. If the access token is valid, the service will authorize the request and process it. If the access token is invalid or has expired, the service will reject the request and send an error message back to the client.
   4. The service may also generate a new access token and send it back to the client with the response. This allows the client to use the new access token in subsequent requests.
   Access tokens are typically generated by an authentication service or identity provider, which is responsible for verifying the identity of users or services and issuing access tokens. The access token usually contains information about the user or service that it represents, as well as a time-to-live (TTL) value that indicates how long the token is valid.
   In addition, to the security benefit, access tokens allow for improved scalability and flexibility in a distributed architecture.
3. Service discovery
   Service discovery is the automatic detection of devices and offered services over a network. Discovery, which minimizes configuration efforts for administrators, is commonly found in microservice architectures and containerization platforms.
   Service discovery is important because individual services are typically deployed independently in microservices architecture and may run on different servers or containers. Without a service discovery mechanism, each service would need to maintain a manually configured list of other services it needs to communicate with, which would be both tedious and error-prone.
   There are different ways to implement service discovery in microservices, but one common approach is to use a service registry. A service registry is a central repository that keeps track of all the services in the system, along with their location and other relevant metadata. When a service needs to communicate with another service, it queries the service registry to find the location of the desired service, and then establishes a connection to it.
   Some popular tools for implementing service discovery and service registries in microservices include Consul, etcd, and ZooKeeper. Additionally, some container orchestration platforms, such as Kubernetes, have built-in support for service discovery.
4. Circuit Breaker pattern
   The circuit breaker pattern is a design pattern used in software development to improve the resilience and fault tolerance of a system. It works by detecting failures in a service or component and temporarily halting access to that service or component. This allows the system to handle the failure gracefully and prevent cascading failures that could bring down the entire system. In Microservices, different services communicate with each other over a network, which can introduce a number of potential failures, including network latency, timeouts, and service failures. The circuit breaker pattern is used to improve the reliability and resilience of the system.
   Once the service or component has recovered, the circuit breaker can be reset, and requests can resume. This pattern helps prevent overloading a service or component that is already experiencing issues and allows the system to gracefully handle unexpected failures.
   By using the circuit breaker pattern, developers can improve the resilience and fault tolerance of the system, reducing the likelihood of downtime or other issues.
5. Distributed Tracing
   Since different services communicate with each other over a network in microservices architecture, a single user request often requires interactions with multiple services.
   The distributed tracing pattern is required to instrument the responses and requests between the services, enabling the system to track each interaction as a trace. This trace has all the information about the service involved, including the time taken to process the request and any errors/exceptions that may have occurred.
   A distributed tracing system typically consists of three main components: a tracer, a collector, and a visualizer. The tracer is embedded within each microservice and records trace data for each request. The collector aggregates this trace data from different services and sends it to the visualizer, which displays the trace data in a way that is easily understandable by humans.
   Distributed tracing helps gain visibility and insight into the flow of requests and responses between different services in a distributed system. This helps developers and operations teams to understand how requests propagate through a complex system and identify performance bottlenecks or errors that may arise as a result.
   Distributed tracing also improves observability, and leads to faster root cause analysis and enhanced collaboration.
6. CQRS and SAGA
   CQRS (Command Query Responsibility Segregation) and Saga are two design patterns used in distributed systems and microservices architecture to improve the scalability, performance, and fault tolerance of the system.
   CQRS separates the responsibility for handling commands (write operations that change the state of the system) from that of handling queries (read operations that retrieve data from the system). In a CQRS architecture, commands are handled by a separate write model, while queries are handled by a separate read model. This separation can improve the scalability of the system by allowing each model to be optimized for its specific task.
   A Saga is a pattern used to manage long-lived transactions that involve multiple services. In a Saga, each service involved in the transaction takes responsibility for its part of the transaction, and a coordinator service manages the overall transaction. The coordinator service communicates with each service to ensure that each step of the transaction is completed successfully. If a step fails, the coordinator service can initiate compensating transactions to undo the steps that have already been completed.