实现目标

  • 多IP解析，负载轮询
  • 自动检查后端服务状态，自动剔除不可用后端
  • 别名配置
  • 上游DNS支持
  • ttl cache 支持

前两点由cousul实现
后两点由dnsmasq实现
别名配置未实现

简单应用

集群配置

10.1.88.84
10.1.88.85
10.1.88.86

consul agent -server -bootstrap-expect=3 -data-dir=/tmp/consul -node=10.1.88.84 -bind=10.1.88.84 -client=0.0.0.0 -datacenter=bj -domain=zhangeamon.com -config-dir=/etc/consul.d -ui
consul agent -server -bootstrap-expect=3 -data-dir=/tmp/consul -node=10.1.88.85 -bind=10.1.88.85 -client=0.0.0.0 -datacenter=bj -domain=zhangeamon.com -join=10.1.88.84 -config-dir=/etc/consul.d -ui
consul agent -server -bootstrap-expect=3 -data-dir=/tmp/consul -node=10.1.88.86 -bind=10.1.88.86 -client=0.0.0.0 -datacenter=bj -domain=zhangeamon.com -join=10.1.88.84 -config-dir=/etc/consul.d -ui

服务发现配置

cat /etc/consul.d.web.json

{
  "services":[
    {
      "id": "web01",
      "name": "web",
      "address": "10.1.88.84",
      "tags": [
        "rails"
       ],
        "check": {
          "name": "SSH",
          "tcp": "10.1.88.84:22",
          "interval": "1s",
          "timeout": "1s",
          "success_before_passing": 3,
          "failures_before_critical": 3
      }
    },
    { 
      "id": "web02",
      "name": "web",
      "address": "10.1.88.85",
      "tags": [
        "rails"
      ],
      "check": {
          "name": "SSH",
          "tcp": "10.1.88.85:8000",
          "interval": "1s",
          "timeout": "1s",
          "success_before_passing": 3,
          "failures_before_critical": 3
      }
     }
  ]
}

加载服务发现配置 consul reload

测试

dig @127.0.0.1 -p 8600 web.service.zhangeamon.com

在 10.1.88.85 启动服务8000端口

python -m SimpleHTTPServer 8000

服务开启时解析到 10.1.88.85 服务关闭时 10.1.88.85 被剔除。

API 服务发现

cat agent-service.json

{
  "ID": "redis1",
  "Name": "redis",
  "Tags": ["primary", "v1"],
  "Address": "10.10.2.11",
  "Port": 8000,
  "Meta": {
    "redis_version": "4.0"
  },
  "EnableTagOverride": true,
  "Check": {
    "checkID": "redis001",
    "name": "redis001",
    "DeregisterCriticalServiceAfter": "1m",
    "ttl":"30s",
    "status": "passing"
  },
  "Weights": {
    "Passing": 10,
    "Warning": 1
  }
}

cat agent-service.json

{
  "ID": "redis1",
  "Name": "redis",
  "Tags": ["primary", "v1"],
  "Address": "10.10.2.11",
  "Port": 8000,
  "Meta": {
    "redis_version": "4.0"
  },
  "EnableTagOverride": true,
  "Check": {
    "DeregisterCriticalServiceAfter": "1m",
    "http": "http://10.10.2.11:8000",
    "Interval": "10s",
    "Timeout": "5s"
  },
  "Weights": {
    "Passing": 10,
    "Warning": 1
  }
}

服务注册

curl     --request PUT     --data @agent-service.json     http://10.10.2.12:8500/v1/agent/service/register?replace-existing-checks=true

ttl 状态维护

curl     --request PUT     --data @agent-service.json     http://10.10.2.12:8500/v1/agent/check/pass/redis001

dnsmasq 配置

vi /etc/dnsmasq.conf

conf-dir=/etc/dnsmasq.d,.rpmnew,.rpmsave,.rpmorig
all-servers
# 多个上游dns配置 后缀为 zhangeamon.com 上游走consul,实现支持上游dns功能
server=119.29.29.29#53
server=/zhangeamon.com/10.1.88.84#8600
server=/zhangeamon.com/10.1.88.85#8600
server=/zhangeamon.com/10.1.88.86#8600
#resolv-file=/etc/resolv.dnsmasq.conf
log-facility=/var/log/dnsmasq/dnsmasq.log
log-async=100
# 缓存配置
cache-size=1000000
#no-hosts
dns-forward-max=1000000
log-queries

#cname 配置未生效
#cname=web.zhangeamon.com,web.service.zhangeamon.com 
#cname=a.a.com,a.b.com
#cname 使用限制说明。本地/etc/hosts
Provide an alias for a "local" DNS name. Note that this _only_ works
# for targets which are names from DHCP or /etc/hosts. Give host
# "bert" another name, bertrand
#cname=bertand,bert

负载均衡

负载均衡指的是多个dns服务同时对外提供服务。

配置nginx转发dns

upstream dns_servers {
  server <UPSTREAM>  weight=2 max_fails=1  fail_timeout=5s;
  server <UPSTREAM>  weight=2 max_fails=1  fail_timeout=5s;
}

server {
  listen 53  udp;
  listen 53; #tcp
  proxy_pass dns_servers;

  proxy_timeout 3s;
  proxy_responses 1;

  error_log <LOG_PATH> error;
}