Help Center/ Cloud Container Engine/ User Guide/ Old Console/ Networking/ Services/ LoadBalancer
Updated on 2023-11-15 GMT+08:00
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LoadBalancer

Scenario

A workload can be accessed from public networks through a load balancer, which is more secure and reliable than EIP.

The LoadBalancer access address is in the format of <IP address of public network load balancer>:<access port>, for example, 10.117.117.117:80.

In this access mode, requests are transmitted through an ELB load balancer to a node and then forwarded to the destination pod through the Service.

Figure 1 LoadBalancer

Notes and Constraints

  • LoadBalancer Services allow workloads to be accessed from public networks through ELB. This access mode has the following restrictions:
    • It is recommended that automatically created load balancers not be used by other resources. Otherwise, these load balancers cannot be completely deleted, causing residual resources.
    • Do not change the listener name for the load balancer in clusters of v1.15 and earlier. Otherwise, the load balancer cannot be accessed.
  • After a Service is created, if the affinity setting is switched from the cluster level to the node level, the connection tracing table will not be cleared. You are advised not to modify the Service affinity setting after the Service is created. If you need to modify it, create a Service again.
  • If the service affinity is set to the node level (that is, externalTrafficPolicy is set to Local), the cluster may fail to access the Service by using the ELB address. For details, see Why a Cluster Fails to Access Services by Using the ELB Address.
  • If you create a LoadBalancer Service on the CCE console, a random node port is automatically generated. If you use kubectl to create a LoadBalancer Service, a random node port is generated unless you specify one.
  • In a CCE cluster, if the cluster-level affinity is configured for a LoadBalancer Service, requests are distributed to the node ports of each node using SNAT when entering the cluster. The number of node ports cannot exceed the number of available node ports on the node. If the Service affinity is at the node level (local), there is no such constraint.
  • When the cluster service forwarding (proxy) mode is IPVS, the node IP cannot be configured as the external IP of the Service. Otherwise, the node is unavailable.

Adding a Service When Creating a Workload

You can set the Service when creating a workload on the CCE console. An Nginx workload is used as an example.

  1. In the Set Application Access step of Creating a Deployment, Creating a StatefulSet, or Creating a DaemonSet, click Add Service and set the following parameters:

    • Access Type: Select LoadBalancer (ELB).
    • Service Name: Specify a Service name, which can be the same as the workload name.
    • Service Affinity:
      • Cluster level: The IP addresses and access ports of all nodes in a cluster can access the workload associated with the Service. Service access will cause performance loss due to route redirection, and the source IP address of the client cannot be obtained.
      • Node level: Only the IP address and access port of the node where the workload is located can access the workload associated with the Service. Service access will not cause performance loss due to route redirection, and the source IP address of the client can be obtained.

    ELB Configuration

    • Elastic Load Balancer: A load balancer automatically distributes Internet access traffic to multiple nodes where the workload is located.

      You can create public network or private network load balancers.

      • Public network: You can select an existing public network load balancer or have the system automatically create a new one.
      • Private network: You can select an existing private network load balancer or have the system automatically create a new private network load balancer.
      The selected or created load balancer must be in the same VPC as the current cluster, and it must match the load balancer type (private or public network).
      • Enterprise Project: Select an enterprise project in which the load balancer is created.
      • Specifications: This field is displayed only when you select Public network and Automatically created for Elastic Load Balancer. You can click to modify the name, specifications, billing mode, and bandwidth of the load balancer.
      • Algorithm Type: Three algorithms are available: weighted round robin, weighted least connections algorithm, or source IP hash.
        • Weighted round robin: Requests are forwarded to different servers based on their weights, which indicate server processing performance. Backend servers with higher weights receive proportionately more requests, whereas equal-weighted servers receive the same number of requests. This algorithm is often used for short connections, such as HTTP services.
        • Weighted least connections: In addition to the weight assigned to each server, the number of connections processed by each backend server is also considered. Requests are forwarded to the server with the lowest connections-to-weight ratio. Building on least connections, the weighted least connections algorithm assigns a weight to each server based on their processing capability. This algorithm is often used for persistent connections, such as database connections.
        • Source IP hash: The source IP address of each request is calculated using the hash algorithm to obtain a unique hash key, and all backend servers are numbered. The generated key allocates the client to a particular server. This enables requests from different clients to be distributed in load balancing mode and ensures that requests from the same client are forwarded to the same server. This algorithm applies to TCP connections without cookies.
      • Sticky Session: This function is disabled by default. You can select Based on source IP address. Listeners ensure session stickiness based on IP addresses. Requests from the same IP address will be forwarded to the same backend server.
      • Health Check: This function is enabled by default. The health check is for the load balancer. By default, the Service ports (Node Port and container port of the Service) are used for health check. You can also specify another port for health check. After the port is specified, a Service port (name: cce-healthz; protocol: TCP) will be added for the Service.
    • Port Settings
      • Protocol: protocol used by the Service.
      • Container Port: port defined in the container image and on which the workload listens. The Nginx application listens on port 80.
      • Access Port: port mapped to the container port at the load balancer's IP address. The workload can be accessed at <Load balancer's IP address>:<Access port>. The port number range is 1–65535.

  2. After the configuration is complete, click OK.
  3. On the workload creation page, click Next: Configure Advanced Settings. On the page displayed, click Create.
  4. After the workload is successfully created, choose Workloads > Deployments or Workloads > StatefulSets on the CCE console. Click the name of the workload to view its details. On the workload details page, click the Services tab and obtain the access address.

    Figure 2 Obtaining the load balancer IP address

  5. Click the access address.

Adding a Service After Creating a Workload

You can set the Service after creating a workload. This has no impact on the workload status and takes effect immediately. The procedure is as follows:

  1. Log in to the CCE console. In the navigation pane, choose Resource Management > Network.
  2. On the Services tab page, click Create Service.

    The parameters are the same as those in Adding a Service When Creating a Workload.

  3. Click Create.

Using kubectl to Create a Service (Using an Existing Load Balancer)

You can set the access type when creating a workload using kubectl. This section uses an Nginx workload as an example to describe how to add a LoadBalancer Service using kubectl.

  1. Use kubectl to connect to the cluster. For details, see Connecting to a Cluster Using kubectl.
  2. Create and edit the nginx-deployment.yaml and nginx-elb-svc.yaml files.

    The file names are user-defined. nginx-deployment.yaml and nginx-elb-svc.yaml are merely example file names.

    vi nginx-deployment.yaml

    apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx 
        name: nginx
      imagePullSecrets:
      - name: default-secret

    vi nginx-elb-svc.yaml

    Before enabling sticky session, ensure that the following conditions are met:

    • The workload protocol is TCP.
    • Anti-affinity has been configured between pods of the workload. That is, all pods of the workload are deployed on different nodes. For details, see Workload-Node Anti-Affinity.
    apiVersion: v1 
kind: Service 
metadata: 
  annotations:
    kubernetes.io/elb.id: 3c7caa5a-a641-4bff-801a-feace27424b6          # Load balancer ID. Replace it with the actual value.
    kubernetes.io/elb.class: performance                               # Load balancer type
  name: nginx 
spec: 
  ports: 
  - name: service0 
    port: 80
    protocol: TCP 
    targetPort: 80
  selector: 
    app: nginx 
  type: LoadBalancer
    Table 1 Key parameters

    Parameter

    Mandatory

    Type

    Description

    kubernetes.io/elb.class

    String

    Select a proper load balancer type as required.

    The value can be:

    • performance: dedicated load balancer, which can be used only in clusters of v1.17 and later.

    kubernetes.io/elb.session-affinity-mode

    No

    String

    Listeners ensure session stickiness based on IP addresses. Requests from the same IP address will be forwarded to the same backend server.

    • Disabling sticky session: Do not set this parameter.
    • Enabling sticky session: Set this parameter to SOURCE_IP, indicating that the sticky session is based on the source IP address.

    kubernetes.io/elb.session-affinity-option

    No

    Table 2 Object

    This parameter specifies the sticky session timeout.

    kubernetes.io/elb.id

    Yes

    String

    This parameter indicates the ID of a load balancer. The value can contain 1 to 100 characters.

    Mandatory when an existing load balancer is to be associated.

    Obtaining the load balancer ID:

    On the management console, click Service List, and choose Networking > Elastic Load Balance. Click the name of the target load balancer. On the Summary tab page, find and copy the ID.

    kubernetes.io/elb.subnet-id

    -

    String

    This parameter indicates the ID of the subnet where the cluster is located. The value can contain 1 to 100 characters.

    • Mandatory when a cluster of v1.11.7-r0 or earlier is to be automatically created.
    • Optional for clusters later than v1.11.7-r0.

    kubernetes.io/elb.lb-algorithm

    No

    String

    This parameter indicates the load balancing algorithm of the backend server group. The default value is ROUND_ROBIN.

    Options:

    • ROUND_ROBIN: weighted round robin algorithm
    • LEAST_CONNECTIONS: weighted least connections algorithm
    • SOURCE_IP: source IP hash algorithm

    When the value is SOURCE_IP, the weights of backend servers in the server group are invalid.

    kubernetes.io/elb.health-check-flag

    No

    String

    Whether to enable the ELB health check.

    Enabled by default.

    • Enabling health check: Leave blank this parameter or set it to on.
    • Disabling health check: Set this parameter to off.

    kubernetes.io/elb.health-check-option

    No

    Table 3 Object

    ELB health check configuration items.

    port

    Yes

    Integer

    Access port that is registered on the load balancer and mapped to the cluster-internal IP address.

    targetPort

    Yes

    String

    Container port set on the CCE console.
    Table 2 Data structure of the elb.session-affinity-option field

    Parameter

    Mandatory

    Type

    Description

    persistence_timeout

    Yes

    String

    Sticky session timeout, in minutes. This parameter is valid only when elb.session-affinity-mode is set to SOURCE_IP.

    Value range: 1 to 60. Default value: 60
    Table 3 Data structure description of the elb.health-check-option field

    Parameter

    Mandatory

    Type

    Description

    delay

    No

    String

    Initial waiting time (in seconds) for starting the health check.

    Value range: 1 to 50. Default value: 5

    timeout

    No

    String

    Health check timeout, in seconds.

    Value range: 1 to 50. Default value: 10

    max_retries

    No

    String

    Maximum number of health check retries.

    Value range: 1 to 10. Default value: 3

    protocol

    No

    String

    Health check protocol.

    Default value: protocol of the associated Service

    Value options: TCP, UDP_CONNECT, or HTTP

    path

    No

    String

    Health check URL. This parameter needs to be configured when the protocol is HTTP.

    Default value: /

    The value contains 1 to 10,000 characters.

  3. Create a workload.

    kubectl create -f nginx-deployment.yaml

    If information similar to the following is displayed, the workload has been created.

    deployment "nginx" created

    kubectl get pod

    If information similar to the following is displayed, the workload is running.

    NAME                     READY     STATUS             RESTARTS   AGE
nginx-2601814895-c1xwh   1/1       Running            0          6s

  4. Create a Service.

    kubectl create -f nginx-elb-svc.yaml

    If information similar to the following is displayed, the Service has been created.

    service "nginx" created

    kubectl get svc

    If information similar to the following is displayed, the access type has been set successfully, and the workload is accessible.

    NAME         TYPE           CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
kubernetes   ClusterIP      10.247.0.1       <none>        443/TCP        3d
nginx        LoadBalancer   10.247.130.196   10.78.42.242   80:31540/TCP   51s

  5. Enter the URL in the address box of the browser, for example, 10.78.42.242:80. 10.78.42.242 indicates the IP address of the load balancer, and 80 indicates the access port displayed on the CCE console.

    The Nginx is accessible.

    Figure 3 Accessing Nginx through the LoadBalancer Service

Using kubectl to Create a Service (Automatically Creating a Load Balancer)

You can add a Service when creating a workload using kubectl. This section uses an Nginx workload as an example to describe how to add a LoadBalancer Service using kubectl.

  1. Use kubectl to connect to the cluster. For details, see Connecting to a Cluster Using kubectl.
  2. Create and edit the nginx-deployment.yaml and nginx-elb-svc.yaml files.

    The file names are user-defined. nginx-deployment.yaml and nginx-elb-svc.yaml are merely example file names.

    vi nginx-deployment.yaml

    apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - image: nginx 
        name: nginx
      imagePullSecrets:
      - name: default-secret

    vi nginx-elb-svc.yaml

    Before enabling sticky session, ensure that the following conditions are met:

    • The workload protocol is TCP.
    • Anti-affinity has been configured between pods of the workload. That is, all pods of the workload are deployed on different nodes. For details, see Workload-Node Anti-Affinity.

    Example of a Service using a dedicated, public network load balancer:

    apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
  namespace: default
  annotations:
    kubernetes.io/elb.class: performance
    kubernetes.io/elb.autocreate: 
        '{
            "type": "public",
            "bandwidth_name": "cce-bandwidth-1626694478577",
            "bandwidth_chargemode": "traffic",
            "bandwidth_size": 5,
            "bandwidth_sharetype": "PER",
            "eip_type": "5_bgp",
            "available_zone": [
                "eu-west-101a"
            ],
            "l4_flavor_name": "L4_flavor.elb.s1.small"
        }'
spec:
  selector:
    app: nginx
  ports:
  - name: cce-service-0
    targetPort: 80
    nodePort: 0
    port: 80
    protocol: TCP
  type: LoadBalancer
    Table 4 Key parameters

    Parameter

    Mandatory

    Type

    Description

    kubernetes.io/elb.class

    String

    Select a proper load balancer type as required.

    The value can be:

    • performance: dedicated load balancer, which can be used only in clusters of v1.17 and later.

    kubernetes.io/elb.subnet-id

    -

    String

    This parameter indicates the ID of the subnet where the cluster is located. The value can contain 1 to 100 characters.

    • Mandatory when a cluster of v1.11.7-r0 or earlier is to be automatically created.
    • Optional for clusters later than v1.11.7-r0.

    kubernetes.io/elb.enterpriseID

    No

    String

    Clusters of v1.15 and later versions support this field. In clusters earlier than v1.15, load balancers are created in the default project by default.

    This parameter indicates the ID of the enterprise project in which the ELB load balancer will be created.

    If this parameter is not specified or is set to 0, resources will be bound to the default enterprise project.

    How to obtain:

    Log in to the management console and choose Enterprise > Project Management on the top menu bar. In the list displayed, click the name of the target enterprise project, and copy the ID on the enterprise project details page.

    kubernetes.io/elb.session-affinity-option

    No

    Table 2 Object

    Sticky session timeout.

    kubernetes.io/elb.autocreate

    Yes

    elb.autocreate object

    Whether to automatically create a load balancer associated with the Service.

    Example:

    • Automatically created public network load balancer:

      {"type":"public","bandwidth_name":"cce-bandwidth-1551163379627","bandwidth_chargemode":"traffic","bandwidth_size":5,"bandwidth_sharetype":"PER","eip_type":"5_bgp","name":"james"}

    • Automatically created private network load balancer:

      {"type":"inner","name":"A-location-d-test"}

    kubernetes.io/elb.lb-algorithm

    No

    String

    This parameter indicates the load balancing algorithm of the backend server group. The default value is ROUND_ROBIN.

    Options:

    • ROUND_ROBIN: weighted round robin algorithm
    • LEAST_CONNECTIONS: weighted least connections algorithm
    • SOURCE_IP: source IP hash algorithm

    When the value is SOURCE_IP, the weights of backend servers in the server group are invalid.

    kubernetes.io/elb.health-check-flag

    No

    String

    Whether to enable the ELB health check.

    Disabled by default.

    • Enabling health check: Leave blank this parameter or set it to on.
    • Disabling health check: Set this parameter to off.

    kubernetes.io/elb.health-check-option

    No

    Table 3 Object

    ELB health check configuration items.

    kubernetes.io/elb.session-affinity-mode

    No

    String

    Listeners ensure session stickiness based on IP addresses. Requests from the same IP address will be forwarded to the same backend server.

    • Disabling sticky session: Do not set this parameter.
    • Enabling sticky session: Set this parameter to SOURCE_IP, indicating that the sticky session is based on the source IP address.

    kubernetes.io/elb.session-affinity-option

    No

    Table 2 Object

    Sticky session timeout.

    kubernetes.io/hws-hostNetwork

    No

    String

    This parameter indicates whether the workload Services use the host network. Setting this parameter to true will enable the load balancer to forward requests to the host network.

    The host network is not used by default. The value can be true or false.

    externalTrafficPolicy

    No

    String

    If sticky session is enabled, add this parameter so that requests are transferred to a fixed node. If a LoadBalancer Service with this parameter set to Local is created, a client can access the target backend only if the client is installed on the same node as the backend.
    Table 5 Data structure of the elb.autocreate field

    Parameter

    Mandatory

    Type

    Description

    name

    No

    String

    Name of the automatically created load balancer.

    Value range: a string of 1 to 64 characters, including lowercase letters, digits, and underscores (_). The value must start with a lowercase letter and end with a lowercase letter or digit.

    Default name: cce-lb+service.UID

    type

    No

    String

    Network type of the load balancer.

    • public: public network load balancer
    • inner: private network load balancer

    Default value: inner

    bandwidth_name

    Yes for public network load balancers

    String

    Bandwidth name. The default value is cce-bandwidth-******.

    Value range: a string of 1 to 64 characters, including lowercase letters, digits, and underscores (_). The value must start with a lowercase letter and end with a lowercase letter or digit.

    bandwidth_chargemode

    No

    String

    Bandwidth billing mode.

    • traffic: billed by traffic

    bandwidth_size

    Yes for public network load balancers

    Integer

    Bandwidth size. The default value is 1 to 2000 Mbit/s. Set this parameter based on the bandwidth range allowed in your region.

    bandwidth_sharetype

    Yes for public network load balancers

    String

    Bandwidth sharing mode.

    • PER: dedicated bandwidth

    eip_type

    Yes for public network load balancers

    String

    EIP type.

    • 5_bgp: dynamic BGP

    available_zone

    Yes

    Array of strings

    AZ where the load balancer is located.

    This parameter is available only for dedicated load balancers.

    l4_flavor_name

    Yes

    String

    Flavor name of the layer-4 load balancer.

    This parameter is available only for dedicated load balancers.

    l7_flavor_name

    No

    String

    Flavor name of the layer-7 load balancer.

    This parameter is available only for dedicated load balancers.

    elb_virsubnet_ids

    No

    Array of strings

    Subnet where the backend server of the load balancer is located. If this parameter is left blank, the default cluster subnet is used.

    Load balancers occupy different number of subnet IP addresses based on their specifications. Therefore, you are not advised to use the subnet CIDR blocks of other resources (such as clusters and nodes) as the load balancer CIDR block.

    This parameter is available only for dedicated load balancers.

    Example:

    "elb_virsubnet_ids": [
   "14567f27-8ae4-42b8-ae47-9f847a4690dd"
 ]

  3. Create a workload.

    kubectl create -f nginx-deployment.yaml

    If information similar to the following is displayed, the workload is being created.

    deployment "nginx" created

    kubectl get po

    If information similar to the following is displayed, the workload is running.

    NAME                     READY     STATUS             RESTARTS   AGE
nginx-2601814895-c1xwh   1/1       Running            0          6s

  4. Create a Service.

    kubectl create -f nginx-elb-svc.yaml

    If information similar to the following is displayed, the Service has been created.

    service "nginx" created

    kubectl get svc

    If information similar to the following is displayed, the access type has been set successfully, and the workload is accessible.

    NAME         TYPE           CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
kubernetes   ClusterIP      10.247.0.1       <none>        443/TCP        3d
nginx        LoadBalancer   10.247.130.196   10.78.42.242   80:31540/TCP   51s

  5. Enter the URL in the address box of the browser, for example, 10.78.42.242:80. 10.78.42.242 indicates the IP address of the load balancer, and 80 indicates the access port displayed on the CCE console.

    The Nginx is accessible.

    Figure 4 Accessing Nginx through the LoadBalancer Service

Why a Cluster Fails to Access Services by Using the ELB Address

If the service affinity of a LoadBalancer Service is set to the node level, that is, the value of externalTrafficPolicy is Local, the ELB address may fail to be accessed from the cluster (specifically, nodes or containers).

This is because when the LoadBalancer Service is created, kube-proxy adds the ELB access address (external-ip) to iptables or IPVS. When the ELB address is accessed from the cluster, the ELB load balancer is not used. Instead, kube-proxy directly forwards the access request. The case depends on which container network model and service forwarding mode you use.

The following methods can be used to solve this problem:

  • (Recommended) In the cluster, use the ClusterIP Service or service domain name for access.
  • Set externalTrafficPolicy of the Service to Cluster, which means cluster-level service affinity. Note that this affects source address persistence. 
    apiVersion: v1 
kind: Service
metadata: 
  annotations:   
    kubernetes.io/elb.class: union
    kubernetes.io/elb.autocreate: '{"type":"public","bandwidth_name":"cce-bandwidth","bandwidth_chargemode":"traffic","bandwidth_size":5,"bandwidth_sharetype":"PER","eip_type":"5_bgp","name":"james"}'
  labels: 
    app: nginx 
  name: nginx 
spec: 
  externalTrafficPolicy: Cluster
  ports: 
  - name: service0 
    port: 80
    protocol: TCP 
    targetPort: 80
  selector: 
    app: nginx 
  type: LoadBalancer
Parent topic: Services