Services

A Service is an abstract way to expose an application running on a set of Pods as a network service. Namely, a Service groups endpoints of these Pods into a single resource, which can be accessed through different ways.

With Kubernetes, you don’t need to modify your application to use an unfamiliar service discovery mechanism. Kubernetes gives Pods their IP addresses and a single DNS name for a set of Pods, and can load-balance across them.

For more information, see the official documentation of Kubernetes.

Access Type

  • Virtual IP: It is based on the unique IP generated by the cluster. A Service can be accessed through this IP inside the cluster. Alternatively, a Service can also be accessed through NodePort and LoadBalancer outside the cluster. This type is suitable for most Services.
  • Headless: The cluster does not generate an IP address for the Service, and the Service is directly accessed through the backend Pod IP of the Service within the cluster. This type is suitable for backend heterogeneous Services, such as Services that need to distinguish between master and slave.

Tip

In KubeSphere, stateful and stateless Services are created with a virtual IP by default. If you want to create a Headless Service, use YAML to configure it directly.

Prerequisites

Service Type

create_service_type

As shown in the image, KubeSphere provides three basic methods to create a Service: Stateless Service, Stateful Service, and External Service. Besides, you can also customize a Service through Specify Workloads and Edit by YAML under Custom Creation.

Stateless Service

Stateless Services are the most commonly used Services in container Services. They define the Pod template to control the Pod status, including rolling updates and rollbacks. A Deployment workload is also created when you create a stateless Service. For more information about stateless Services, see Deployments.

Stateful Service

Stateful Services are used to manage stateful applications, ensuring ordered and graceful deployment and scaling. They also provide stable persistent storage and network identifiers. A StatefulSet workload is also created when you create a stateful Service. For more information about stateful Services, see StatefulSets.

External Service

Different from stateless and stateful Services, an ExternalName Service maps a Service to a DNS name instead of a selector. You need to specify these Services in the ExternalName field, indicated by externalName in the YAML file.

Specify Workloads

Create a Service with existing Pods.

Edit by YAML

Create a Service directly with YAML. You can upload and download YAML configuration files to and from the console.

Tip

The value of annotations:kubesphere.io/serviceType keywords can be defined as: statelessservice, statefulservice, externalservice and None.

Create a Stateless Service

Step 1: Open Dashboard

  1. Go to Services under Application Workloads of a project and click Create.

services_lists

  1. Click Stateless Service.

stateless_form

Note

The steps of creating a stateful Service and a stateless Service are basically the same. This example only presents the process of creating a stateless Service for demonstration purpose.

Step 2: Input Basic Information

  1. In the dialogue that appears, you can see the filed Version prepopulated with v1. You need to define a name for the Service, such as demo-service. When you finish, click Next to continue.

stateless_form_1

  • Name: The name of the Service and Deployment, which is also the unique identifier.
  • Alias: The alias name of the Service, making resources easier to identify.
  • Version: It can only contain lowercase letters and numbers. The maximum length of characters is set to 16.

Tip

The value of Name is used in both configurations, one for Deployment and the other for Service. You can see the manifest file of the Deployment and the Service by enabling Edit Mode in the top right corner. Below is an example file for your reference.

  1. kind: Deployment
  2. metadata:
  3.   labels:
  4.     version: v1
  5.     app: xxx
  6.   name: xxx-v1
  7. spec:
  8.   selector:
  9.     matchLabels:
  10.       version: v1
  11.       app: xxx
  12.   template:
  13.     metadata:
  14.       labels:
  15.         version: v1
  16.         app: xxx
  17. ---
  18. kind: Service
  19. metadata:
  20.   labels:
  21.     version: v1
  22.     app: xxx
  23.   name: xxx
  24. spec:
  25.     metadata:
  26.       labels:
  27.         version: v1
  28.         app: xxx

Step 3: Set Image

To add a container image for the Service, see Set Image for details.

stateless_form_2.png

Tip

For more information about explanations of dashboard properties, see Container Image Settings directly.

Step 4: Mount Volumes

To mount a volume for the Service, see Mount Volumes for details.

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Step 5: Configure Advanced Settings

You can set a policy for node scheduling and add metadata which is the same as explained in Deployments. For a Service, you can see two additional options available.

stateless_form_4

Internet Access

You can expose a Service externally through two methods, NodePort and LoadBalancer.

  • NodePort: A Service is exposed on each node’s IP address at a static port.

  • LoadBalancer: Clients send requests to the IP address of a load balancer.

Note

This value is specified by .spec.type. If you select LoadBalancer, you need to add annotations for it at the same time.

Enable Sticky Session

You may want to route all traffic sent from a single client session to the same instance of an app which runs across multiple replicas. This makes better use of caches as it reduces latency. This behavior of load balancing is called Sticky Sessions.

You can set the maximum session sticky time in this field, specified by .spec.sessionAffinityConfig.clientIP.timeoutSeconds in the manifest file, which defaults to 10800.

Check Service Details

Detail Page

  1. After a Service is created, you can click the three dots on the right to further edit it, such as its metadata (excluding Name), YAML, port, and Internet access.

stateless_finish

  • Edit: View and edit the basic data.
  • Edit YAML: View, upload, download, or update the YAML file.
  • Edit Service: View the access type and set selectors and ports.
  • Edit Internet Access: Edit the service Internet access method.
  • Delete: When you delete a Service, associated resources will be displayed. If you check them, they will be deleted together with the Service.
  1. Click the name of the Service and you can go to its detail page.

stateless_finish

  • Click More to expand the drop-down menu which is the same as the one in the Service list.
  • The Pod list provides detailed information of the Pod (status, node, Pod IP and resource usage).
  • You can view the container information by clicking a Pod item.
  • Click the container log icon to view output logs of the container.
  • You can view the Pod detail page by clicking the Pod name.