An API Gateway is a server that acts as a ‘gate’ between applications and microservices, facilitating communication between them. It is the main entry point for data flowing into your applications from various sources, and it helps streamline and manage these data interactions. The concept of an API Gateway is particularly significant in microservices architecture, where it helps manage and route requests to the right services.
How does it work?
An API Gateway works as a reverse proxy that accepts API calls, routes them to the appropriate microservices, and then consolidates the results to respond to the client. Essentially, it takes requests from a client, determines which services are needed, passes the requests to the services, and then aggregates the results. This is done to decouple clients from services, thus providing a level of abstraction.
The API Gateway can also provide functionalities such as:
- Request routing based on URI, IP, parameters, etc.
- Request aggregation to reduce the number of requests/roundtrips.
- Authentication and Authorization to secure services.
- Rate limiting to protect services from being overwhelmed.
- Caching to improve performance.
- Request shaping and manipulation to transform requests.
- Logging and monitoring to provide visibility into operations.
What are the main benefits?
- Reduced Complexity: API Gateways simplify interactions between clients and services by providing a single entry point for clients. This eliminates the need for clients to manage multiple service endpoints.
- Improved Security: API Gateways provide mechanisms to secure microservices through features like API Key management, JWT validation, and rate limiting.
- Enhanced Performance: API Gateways can improve performance by implementing caching, reducing network round trips through aggregation, and compressing responses.
- Manageability: They provide a centralized location for cross-cutting concerns, making it easier to manage, monitor, and scale your APIs.
- Insights and Analytics: By logging all the incoming and outgoing traffic, API Gateways enable comprehensive analytics and visibility into your API ecosystem.
How is it used in a microservices architecture?
In a microservices architecture, each microservice typically provides a unique service, and clients may need to interact with multiple services to complete a task. The API Gateway is handy here as it provides a single entry point for all clients.
The API Gateway can handle requests in one of two ways:
- Routing: The gateway can route requests to the appropriate microservices.
- Aggregation: The gateway can aggregate responses from multiple microservices and return a combined response to the client.
This not only simplifies the client but also allows microservices to evolve independently, as changes to service implementation are hidden behind the gateway.
How is it useful in Kubernetes?
Kubernetes (K8s) is an open-source platform for managing containerized workloads and services. While Kubernetes has built-in service discovery, using an API Gateway can further enhance the accessibility and usability of your services.
In a Kubernetes environment, an API Gateway can help with the following:
- Service discovery: API Gateway can automatically discover services running in your Kubernetes cluster and route traffic to them.
- Load balancing: It can distribute traffic among pods running the same service.
- Authentication and Authorization: It can handle these before the requests reach your services.
- Canary deployments and A/B testing: It can route different percentages of traffic to different service versions.
How is it different from Ingress Gateway or Ingress Controller?
An Ingress in Kubernetes is an API object that manages external access to the services in a cluster, typically through HTTP. An Ingress Controller is responsible for fulfilling the Ingress, usually with a load balancer.
On the other hand, an Ingress Gateway is a concept used in service mesh architectures (like Istio) to define the entry point for traffic into the mesh.
While the role of API Gateways and Ingress Controllers might seem similar, they serve different purposes. Ingress Controllers are specifically designed to route traffic within a Kubernetes cluster. In contrast, API Gateways are more about providing a single entry point for external services to communicate with the microservices inside the system, along with other capabilities like request transformation, aggregation, rate limiting, etc.
It is also common to use an API Gateway with an Ingress Controller, where the Ingress Controller manages the internal routing within the cluster, and the API Gateway manages external traffic coming into the cluster.
Is it the same as Gateway API in K8S?
No, it’s not the same. Gateway API in Kubernetes is a set of CRDs (Custom Resource Definitions) that aim to provide more prosperous and expressive capabilities than the existing Ingress API. The Gateway API is designed to evolve the Ingress model by adding more features and addressing its limitations. It is not the same as an API Gateway.
What about Service Mesh vs API Gateway?
Service Mesh and API Gateway are tools that help manage and control traffic in a microservices architecture, but they are used for different purposes and scopes.
A Service Mesh manages internal service-to-service communication in a microservices architecture, providing features like load balancing, service discovery, traffic management, and fault injection. Service Mesh works at the application networking layer, primarily focusing on network-level operations. Istio and Linkerd are examples of Service Mesh.
On the other hand, API Gateway is more about managing incoming requests from external clients and routing them to appropriate services. It operates at the edge of your system and is more concerned with API-level operations, such as API routing, rate limiting, authentication, and API composition. Kong and Apigee are examples of API Gateways.
While there is some overlap in the features they provide, they are complementary to each other in a microservices architecture.
What is the difference between API Gateway and API Management?
While the terms API Gateway and API Management are sometimes used interchangeably, they refer to different aspects of API infrastructure.
An API Gateway is a technical component focused on the runtime for route requests, secure APIs, aggregate data, etc. It is more about the operational aspects of running an API.
API Management, on the other hand, is a broader term encompassing the creation, maintenance, and enforcement of API policies across the entire lifecycle of an API. It includes components like a developer portal, policy management, analytics, etc., in addition to the API Gateway.
So, in a nutshell, API Gateway is part of a broader API Management solution.
How to Choose an API Gateway?
Choosing an API Gateway depends on various factors, including but not limited to your specific use cases, requirements, the technology stack you are using, and your team’s expertise. Here are some considerations:
- Performance: Does the API Gateway meet your performance requirements regarding latency, throughput, etc.?
- Scalability: Can it scale as your application grows and handle increased traffic?
- Feature set: Does it provide the features you need, such as rate limiting, authentication, request transformation, etc.?
- Ease of use: Is configuring, deploying, and managing easy? Does it provide a user-friendly interface or a robust API for configuration?
- Compatibility: Does it support the technologies and protocols that your application uses? Is it compatible with your existing infrastructure?
- Security: Does it provide robust security mechanisms to protect your APIs?
- Community and support: Is there a strong community and good support from the provider?
What are the best options in terms of features?
There are many great API Gateway solutions, both open-source and commercial. Here are some of them:
- Kong: Kong is a famous open-source API Gateway platform designed for multi-cloud or hybrid environments.
- KrakenD: KrakenD is an ultra-performant API Gateway framework in Go. It is designed to be minimalist and able to handle a high volume of requests, with functionalities like API aggregation, service discovery, and more.
- Express Gateway: A microservices API Gateway built on top of Express.js. It’s highly customizable, with features like rate limiting, JWT validation, and circuit breaker support.
- Zuul: Developed by Netflix, Zuul is a gateway service that provides dynamic routing, monitoring, resiliency, security, and more.
- Ambassador: Designed specifically for Kubernetes, Ambassador is a high-performance, open-source API Gateway built on the Envoy Proxy. Ambassador supports various features needed for Edge Stack routing in microservice architectures.
- Tyk: Tyk is an open-source, full-lifecycle API management platform.
- AWS API Gateway: A fully managed service by AWS to create, publish, maintain, monitor, and secure APIs.
- Apigee: Apigee, by Google Cloud, is a full-fledged API platform that includes an API Gateway and comprehensive API management tools.
- Azure API Management: A solution from Microsoft Azure offering full-lifecycle API management.
What is the main difference between reverse proxy and API Gateway?
A reverse proxy is a server that sits between client devices and a web server, forwarding client requests to the web server and returning the server’s responses to the clients.
On the other hand, an API Gateway is a more advanced form of a reverse proxy. In addition to routing requests like a reverse proxy, an API Gateway can aggregate responses from multiple microservices, manage API versions, implement security protocols, and perform other tasks specific to business logic.
In summary, while all API Gateways can function as a reverse proxy, not all reverse proxies can serve as API Gateways. The API Gateway is more suited for scenarios requiring more business-related functionality.