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Last updated on June 26, 2023
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Ingress is a Kubernetes service that allows external traffic to reach the individual services inside a cluster. It is similar to a load balancer, but there are important differences between them. Kubernetes Ingress allows you to configure deployments in front of your applications, which can be accessed by external users. Ingress can be used to publish web services, expose services to internal clients, or even route traffic to different microservices. Kubernetes Ingress Controllers are responsible for managing ingress resources (e.g., routing rules, load balancing). The ingress controller watches the Kubernetes API server and adds or removes ingress resources as appropriate.
In simpler terms, ingress is a Kubernetes concept that describes the point of entry for external traffic. This term is commonly used by Kubernetes users to refer to the API server in a cluster that handles external requests and load balances them appropriately.
If you look at the word "ingress" you can see that it is a word that means to go in. So, when you use Kubernetes to let things go in and out of our system, you call this ingress.
Imagine having multiple microservices running in a Kubernetes cluster, each serving different functionalities. These microservices need to be accessible from outside the cluster. This is where Kubernetes Ingress comes into play.
To understand how Kubernetes Ingress works, let’s use an analogy. Imagine you live in an apartment building with multiple units. Each unit has its own unique address (service). However, there’s only one main entrance (Ingress) through which all visitors enter the building.
Similarly, in a Kubernetes cluster, all external traffic enters through a single point known as the Ingress controller. The Ingress controller then checks incoming requests against defined rules and routes them to the corresponding services and pods within the cluster.
Here is a quick rundown of how ingress in Kubernetes works:
1.Ingress Controller: To make use of Ingress, you need an Ingress controller. The Ingress controller is responsible for implementing the rules defined in your Ingress resources and routing the traffic accordingly. There are various Ingress controllers available, such as Nginx, Traefik, or HAProxy.
2. Defining Rules: Once you have an Ingress controller set up, you can define rules using Kubernetes’ Ingress resource. These rules specify how incoming requests should be handled and routed within your cluster. Each rule consists of a host and a set of paths that map to different backend services.
3.Routing Traffic: When an external request comes in, it first reaches the load balancer or DNS server that forwards it to the appropriate node in your cluster where the Ingress controller resides.
4. Ingress Rules Evaluation: The Ingress controller receives the request and evaluates it against the defined rules in your Ingress resources. It looks at factors like the requested hostname and path to determine which backend service should handle the request.
5. Forwarding Requests: Once the appropriate backend service is identified, the Ingress controller routes the request to that service by forwarding it internally within your cluster.
6. Load Balancing: If you have multiple instances of a service running, the Ingress controller can handle load balancing by distributing incoming requests evenly across those instances.
7. TLS Termination: Additionally, Kubernetes Ingress supports secure connections using TLS termination. You can configure SSL certificates for specific hostnames to ensure secure communication between clients and your services.
8. Customization:Kubernetes Ingress offers various options for customization. For example, you can set up rate limiting, authentication, or URL rewriting rules to control how requests are handled.
To define routing rules for your applications using Kubernetes Ingress, you make use of Ingress resources. These resources are created by writing YAML files that specify various configurations such as hostname-based routing, path-based routing, SSL termination, load balancing techniques, and more.
For example, you can create an Ingress resource that directs all requests coming from example.com to a specific service within your cluster. You can also configure path-based routing so that requests going to example.com/api are routed to a different service.
Now that you understand how Ingress and Ingress resource’s function, it’s important to mention Ingress controllers. An Ingress controller is responsible for implementing the actual routing rules defined in the Ingress resources.
There are several Ingress controllers available in the Kubernetes ecosystem, such as Nginx Ingress Controller, Traefik, and HAProxy. You can choose the one that best fits your requirements or use the default controller provided by your Kubernetes distribution. Read on to know the details of these controllers:
Nginx Ingress Controller
Nginx is a well-known web server that can also act as an Ingress Controller. It provides powerful load-balancing capabilities, SSL termination, and URL rewriting among other useful features. If you are already familiar with Nginx, this controller is worth considering.
Traefik
Traefik is another popular option that stands out with its simplicity and flexibility. It integrates seamlessly with the Kubernetes ecosystem and offers automatic service discovery, Let’s Encrypt support for SSL certificates, and dynamic configuration updates. Plus, it has built-in support for multiple providers like Docker, Swarm, and Kubernetes.
HAProxy
For those who prefer a battle-tested solution with a long history of reliability, HAProxy might be the right choice. It excels at handling high volumes of traffic while ensuring low latency and high availability. It also supports advanced load-balancing algorithms and SSL offloading.
Ambassador
Ambassador takes a different approach by focusing on microservices architecture. It provides powerful features like automatic API documentation generation, rate limiting, circuit breaking, and observability through integration with tools like Prometheus.
A Kubernetes Ingress controller acts as a gateway or entry point for external requests to reach the appropriate services within your cluster.
Here’s how it works:
1. Routing Configuration: To begin with, you define an Ingress resource in Kubernetes that specifies how incoming requests should be handled. This includes rules for routing traffic based on specific paths or hostnames.
2.Load Balancing: The ingress controller receives incoming requests from the external world and distributes them to the appropriate backend services based on the routing configuration defined in the Ingress resource. It ensures that each request is efficiently load-balanced across multiple instances of your application.
3.SSL Termination: If you need to secure your connections using HTTPS, the ingress controller can handle SSL termination by decrypting incoming encrypted traffic and forwarding it to your application over HTTP within the cluster.
4. Path-Based Routing: The ingress controller allows you to route requests based on specific paths defined in the Ingress resource. For example, you can configure different paths like /api or /app to be directed to separate services within your cluster.
5. Virtual Hosts: You can also configure virtual hosts (hostnames) in the Ingress resource, enabling you to direct requests coming from different domains or subdomains to different backend services.
6.ngress Controller Implementation: There are various implementations of ingress controllers available, such as Nginx Ingress Controller, Traefik, or HAProxy. Each implementation has its own set of features and configuration options.
7. Dynamic Updates: One great advantage of using an ingress controller is that it allows dynamic updates without modifying your application code. You can add, modify, or remove routing rules in the Ingress resource, and the controller will automatically apply these changes to ensure proper routing of incoming traffic.
Ingress in Kubernetes provides a wide array of use cases. These are detailed below:
Seamless Load Balancing
One of the primary use cases for Ingress is load balancing. Let’s say you have multiple pods running your application, and you want to distribute incoming traffic evenly among them. With Ingress, you can easily achieve this by configuring rules that route requests to specific pods based on certain criteria like path or host.
SSL/TLS Termination
Securing your application with HTTPS is essential to protect sensitive data. However, managing SSL certificates can be cumbersome when dealing with multiple services within Kubernetes. Ingress simplifies this by acting as a termination point for SSL/TLS connections. It terminates encrypted traffic and then forwards it to the appropriate service over an unencrypted connection.
URL-Based Routing
In some scenarios, you may have multiple applications running on different paths or domain names in your cluster. Ingress allows you to define rules that map specific URLs to corresponding services or pods. This enables users to access different applications through a single entry point without exposing their internal structure.
Content-Based Routing
Sometimes, you may need more advanced routing capabilities based on request headers or other parameters. Ingress provides powerful features like content-based routing, allowing you to direct traffic based on specific headers or other request attributes. This flexibility opens up possibilities for implementing complex routing patterns tailored to your application’s needs.
Rate Limiting and Traffic Shaping
Controlling and limiting incoming traffic is crucial for maintaining service availability and preventing abuse. With Ingress, you can apply rate-limiting policies at the edge of your cluster, ensuring fair distribution of resources among clients while protecting against potential denial-of-service attacks.
External Authentication and Authorization
Ingress can also act as a gateway for external authentication and authorization mechanisms. This means you can integrate it with external identity providers or access control systems to enforce security policies before traffic reaches your applications.
Let’s explore some examples to understand how Ingress can simplify your routing needs.
Example 1: Basic Routing
Imagine you have a Kubernetes cluster with multiple microservices running. You want to expose these services to the outside world using a single IP address and domain name. Here’s where Ingress shines:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: my-ingress
spec:
rules:
- host: example.com
http:
paths:
- pathType: Prefix
path: "/service1"
backend:
service:
name: service1
port:
number: 80
- pathType: Prefix
path: "/service2"
backend:
service:
name: service2
port:
number: 80
With this simple configuration, any request coming to example.com/service1 will be routed to service1, while requests to example.com/service2 will go to service2.
Example 2: SSL/TLS Termination
Security is essential when exposing your services over the internet. Fortunately, Ingress allows you to easily handle SSL/TLS encryption and termination. Take a look at this example:
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: my-ingress-ssl
spec:
tls:
- hosts:
- example.com
secretName: my-tls-secret
rules:
- host: example.com
http:
paths:
- pathType: Prefix
path: "/"
backend:
service:
name: my-service
port:
number: 80
In this case, we’re using the tls section to specify that we want to use SSL/TLS encryption for example.com. The actual SSL/TLS certificate is stored in a secret called my-tls-secret. Now you can securely access your services over HTTPS!
Kubernetes Ingress provides a powerful and flexible way to manage external access to your applications running in a cluster. By leveraging the capabilities of an Ingress controller and defining routing rules through Ingress resources, you can easily direct incoming traffic to the appropriate services within your cluster. Armed with this knowledge, you’re well-equipped to start exploring and utilizing KubernetesIngress in your own projects! Do you want to learn more about what is Ingress in Kubernetes? With a DevOps certification, you can acquire all the details. Know more about DevOps training course here.
1. What is Ingress vs load balancer?
Load balancers are external to a cluster, whereas ingress is a native object. Also, they can route to multiple services. However, the load balancer can route to only a single service.
2. Does ingress require a load balancer?
Yes, to deliver the application to clients outside the Kubernetes cluster, a load balancer is required.
3. What is ingress vs egress in Kubernetes?
Ingress refers to the incoming traffic in the pod, whereas egress refers to the outgoing traffic.
4. Do I need ingress for Kubernetes?
You will need an ingress controller to gather traffic in your Kubernetes cluster.
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