Kong提供了两种负载均衡方案：

基于DNS的负载均衡

当使用基于DNS的负载均衡时，上游服务的注册是在Kong之外完成，而Kong只接收来自DNS服务器的负载均衡域名解析。使用包含主机名（而不是IP地址）URL定义的每个API将自动使用基于DNS的负载均衡。

Ring-Balancer环形均衡器

使用环形均衡器时，上游服务的添加和删除将由Kong处理，不需要进行DNS域名解析（当然如果target配置为域名也需要解析域名，但不需要DNS实现负载均衡）。Kong将扮演服务注册中心的角色。使用upstream和target配置服务。

加权循环算法：默认情况下环形均衡器将使用加权循环的方案。
散列算法：以none、consumer、IP或者header为输入的散列算法。none就是加权循环算法。

负载均衡应用

蓝绿部署Blue-Green Deployments

可以通过通过定义蓝upstream和绿upstream。然后通过更新Kong Service，切换host对应的upstrean来达到蓝绿的快速切换。

金丝雀发布Canary Releases

直接使用环形均衡器，通过调整target的权重，允许一个平滑和可控的金丝雀环境。

下面验证一下Ring-Balancer环形均衡器。先创建两个echo服务，为了验证负载均衡，两个echo服务的名称定为echo-v1和echo-v2，其port分别为8080和8081。

vi echo-v1-service.yaml
apiVersion: v1
kind: Service
metadata:
  labels:
    app: echo-v1
  name: echo-v1
spec:
  ports:
  - port: 8080
    name: http
    protocol: TCP
    targetPort: 8080
  selector:
    app: echo-v1
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: echo-v1
  name: echo-v1
spec:
  replicas: 1
  selector:
    matchLabels:
      app: echo-v1
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: echo-v1
    spec:
      containers:
      - image: e2eteam/echoserver:2.2
        name: echo-v1
        ports:
        - containerPort: 8080
        env:
          - name: NODE_NAME
            valueFrom:
              fieldRef:
                fieldPath: spec.nodeName
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          - name: POD_NAMESPACE
            valueFrom:
              fieldRef:
                fieldPath: metadata.namespace
          - name: POD_IP
            valueFrom:
              fieldRef:
                fieldPath: status.podIP
        resources: {}

vi echo-v2-service.yaml
apiVersion: v1
kind: Service
metadata:
  labels:
    app: echo-v2
  name: echo-v2
spec:
  ports:
  - port: 8081
    name: http
    protocol: TCP
    targetPort: 8080
  selector:
    app: echo-v2
---
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: echo-v2
  name: echo-v2
spec:
  replicas: 1
  selector:
    matchLabels:
      app: echo-v2
  strategy: {}
  template:
    metadata:
      creationTimestamp: null
      labels:
        app: echo-v2
    spec:
      containers:
      - image: e2eteam/echoserver:2.2
        name: echo-v2
        ports:
        - containerPort: 8080
        env:
          - name: NODE_NAME
            valueFrom:
              fieldRef:
                fieldPath: spec.nodeName
          - name: POD_NAME
            valueFrom:
              fieldRef:
                fieldPath: metadata.name
          - name: POD_NAMESPACE
            valueFrom:
              fieldRef:
                fieldPath: metadata.namespace
          - name: POD_IP
            valueFrom:
              fieldRef:
                fieldPath: status.podIP
        resources: {}

kubectl apply -f echo-v1-service.yaml
kubectl apply -f echo-v2-service.yaml

创建一个upstream，名称为echo-upstream。

curl -X POST \
  --url http://192.168.1.55:32444/upstreams \
  --data "name=echo-upstream" \
  -s | python -m json.tool
{
    "algorithm": "round-robin",
    "created_at": 1577502909,
    "hash_fallback": "none",
    "hash_fallback_header": null,
    "hash_on": "none",
    "hash_on_cookie": null,
    "hash_on_cookie_path": "/",
    "hash_on_header": null,
    "healthchecks": {
        "active": {
            "concurrency": 10,
            "healthy": {
                "http_statuses": [
                    200,
                    302
                ],
                "interval": 0,
                "successes": 0
            },
            "http_path": "/",
            "https_sni": null,
            "https_verify_certificate": true,
            "timeout": 1,
            "type": "http",
            "unhealthy": {
                "http_failures": 0,
                "http_statuses": [
                    429,
                    404,
                    500,
                    501,
                    502,
                    503,
                    504,
                    505
                ],
                "interval": 0,
                "tcp_failures": 0,
                "timeouts": 0
            }
        },
        "passive": {
            "healthy": {
                "http_statuses": [
                    200,
                    201,
                    202,
                    203,
                    204,
                    205,
                    206,
                    207,
                    208,
                    226,
                    300,
                    301,
                    302,
                    303,
                    304,
                    305,
                    306,
                    307,
                    308
                ],
                "successes": 0
            },
            "type": "http",
            "unhealthy": {
                "http_failures": 0,
                "http_statuses": [
                    429,
                    500,
                    503
                ],
                "tcp_failures": 0,
                "timeouts": 0
            }
        }
    },
    "id": "d440cf4f-bf3a-4127-b610-4e811e5231c2",
    "name": "echo-upstream",
    "slots": 10000,
    "tags": null
}

为echo-upstream上游服务创建两个负载均衡target，分别对应以上创建的两个kubernetes的echo-v1和echo-v2服务。注意两个target的权重，是150:50。

curl -X POST \
  --url http://192.168.1.55:32444/upstreams/echo-upstream/targets \
  --data "target=echo-v1:8080" \
  --data "weight=150" \
  -s | python -m json.tool
{
    "created_at": 1577503409.365,
    "id": "97f5c06a-a4a3-4734-ae3d-eac95a78f6f8",
    "target": "echo-v1:8080",
    "upstream": {
        "id": "d440cf4f-bf3a-4127-b610-4e811e5231c2"
    },
    "weight": 150
}

curl -X POST \
  --url http://192.168.1.55:32444/upstreams/echo-upstream/targets \
  --data "target=echo-v2:8081" \
  --data "weight=50" \
  -s | python -m json.tool
{
    "created_at": 1577503417.043,
    "id": "e09063bf-634b-4dbb-a95d-71b5e9526cec",
    "target": "echo-v2:8081",
    "upstream": {
        "id": "d440cf4f-bf3a-4127-b610-4e811e5231c2"
    },
    "weight": 50
}

创建service，其中host对应以上创建的echo-upstream。

curl -X POST \
  --url http://192.168.1.55:32444/services/ \
  --data "name=echo-service" \
  --data "host=echo-upstream" \
  -s | python -m json.tool
{
    "client_certificate": null,
    "connect_timeout": 60000,
    "created_at": 1577503779,
    "host": "echo-upstream",
    "id": "1f47b93c-b677-4990-9cbc-4504cbd89f6d",
    "name": "echo-service",
    "path": null,
    "port": 80,
    "protocol": "http",
    "read_timeout": 60000,
    "retries": 5,
    "tags": null,
    "updated_at": 1577503779,
    "write_timeout": 60000
}

创建路由。

curl -X POST \
  --url http://192.168.1.55:32444/services/echo-service/routes \
  --data 'name=echo-service-route' \
  --data "paths[]=/foo" \
  -s | python -m json.tool
{
    "created_at": 1577503971,
    "destinations": null,
    "headers": null,
    "hosts": null,
    "https_redirect_status_code": 426,
    "id": "56861fa1-a605-4bb7-a7f9-3726ed41b762",
    "methods": null,
    "name": "echo-service-route",
    "paths": [
        "/foo"
    ],
    "preserve_host": false,
    "protocols": [
        "http",
        "https"
    ],
    "regex_priority": 0,
    "service": {
        "id": "1f47b93c-b677-4990-9cbc-4504cbd89f6d"
    },
    "snis": null,
    "sources": null,
    "strip_path": true,
    "tags": null,
    "updated_at": 1577503971
}

测试一下效果。根据结果看echo-v1 : echo-v2基本上符合3 ： 1。

curl -i http://192.168.1.55:32080/foo
HTTP/1.1 200 OK
Content-Type: text/plain; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
Date: Sat, 28 Dec 2019 03:34:33 GMT
Server: echoserver
X-Kong-Upstream-Latency: 44
X-Kong-Proxy-Latency: 4
Via: kong/1.3.0

Hostname: echo-v1-7db89db86-5xvcw

Pod Information:
        node name:      k8s-node2
        pod name:       echo-v1-7db89db86-5xvcw
        pod namespace:  default
        pod IP: 10.244.2.12

Server values:
        server_version=nginx: 1.14.2 - lua: 10015

Request Information:
        client_address=10.244.1.14
        method=GET
        real path=/
        query=
        request_version=1.1
        request_scheme=http
        request_uri=http://echo-v1:8080/

Request Headers:
        accept=*/*
        connection=keep-alive
        host=echo-v1:8080
        user-agent=curl/7.29.0
        x-forwarded-for=10.244.0.0
        x-forwarded-host=192.168.1.55
        x-forwarded-port=8000
        x-forwarded-proto=http
        x-real-ip=10.244.0.0

Request Body:
        -no body in request-

curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v2-644b65df68-css5k
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v2-644b65df68-css5k
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v2-644b65df68-css5k
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v2-644b65df68-css5k
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v2-644b65df68-css5k
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v2-644b65df68-css5k
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw
curl -i http://192.168.1.55:32080/foo -s | grep "pod name:"
        pod name:       echo-v1-7db89db86-5xvcw

Kong系列-07-负载均衡

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