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Markdown
254 lines
9.2 KiB
Markdown
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<!--
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#
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# Licensed to the Apache Software Foundation (ASF) under one or more
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# contributor license agreements. See the NOTICE file distributed with
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# this work for additional information regarding copyright ownership.
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# The ASF licenses this file to You under the Apache License, Version 2.0
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# (the "License"); you may not use this file except in compliance with
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# the License. You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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-->
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[English](discovery.md)
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# 集成服务发现注册中心
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* [**摘要**](#摘要)
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* [**如何扩展注册中心**](#如何扩展注册中心)
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* [**基本步骤**](#基本步骤)
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* [**以 Eureka 举例**](#以-Eureka-举例)
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* [**实现 eureka.lua**](#实现-eurekalua)
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* [**Eureka 与 APISIX 之间数据转换逻辑**](#Eureka-与-APISIX-之间数据转换逻辑)
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* [**注册中心配置**](#注册中心配置)
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* [**选择注册中心**](#选择注册中心)
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* [**Eureka 的配置**](#Eureka-的配置)
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* [**upstream 配置**](#upstream-配置)
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## 摘要
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当业务量发生变化时，需要对上游服务进行扩缩容，或者因服务器硬件故障需要更换服务器。如果网关是通过配置来维护上游服务信息，在微服务架构模式下，其带来的维护成本可想而知。再者因不能及时更新这些信息，也会对业务带来一定的影响，还有人为误操作带来的影响也不可忽视，所以网关非常必要通过服务注册中心动态获取最新的服务实例信息。架构图如下所示：
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1. 服务启动时将自身的一些信息，比如服务名、IP、端口等信息上报到注册中心；各个服务与注册中心使用一定机制（例如心跳）通信，如果注册中心与服务长时间无法通信，就会注销该实例；当服务下线时，会删除注册中心的实例信息；
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2. 网关会准实时地从注册中心获取服务实例信息；
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3. 当用户通过网关请求服务时，网关从注册中心获取的实例列表中选择一个进行代理；
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常见的注册中心：Eureka, Etcd, Consul, Nacos, Zookeeper等
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## 如何扩展注册中心？
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### 基本步骤
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APISIX 要扩展注册中心其实是件非常容易的事情，其基本步骤如下：
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1. 在 `apisix/discovery/` 目录中添加注册中心客户端的实现；
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2. 实现用于初始化的 `_M.init_worker()` 函数以及用于获取服务实例节点列表的 `_M.nodes(service_name)` 函数；
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3. 将注册中心数据转换为 APISIX 格式的数据；
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### 以 Eureka 举例
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#### 实现 eureka.lua
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首先在 `apisix/discovery/` 目录中添加 [`eureka.lua`](../apisix/discovery/eureka.lua);
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然后在 `eureka.lua` 实现用于初始化的 `init_worker` 函数以及用于获取服务实例节点列表的 `nodes` 函数即可：
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```lua
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local _M = {
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version = 0.1,
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}
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function _M.nodes(service_name)
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... ...
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end
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function _M.init_worker()
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... ...
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end
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return _M
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```
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#### Eureka 与 APISIX 之间数据转换逻辑
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APISIX是通过 `upstream.nodes` 来配置上游服务的，所以使用注册中心后，通过注册中心获取服务的所有 node 后，赋值给 `upstream.nodes` 来达到相同的效果。那么 APISIX 是怎么将 Eureka 的数据转成 node 的呢？ 假如从 Eureka 获取如下数据：
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```json
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{
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"applications": {
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"application": [
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{
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"name": "USER-SERVICE", # 服务名称
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"instance": [
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{
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"instanceId": "192.168.1.100:8761",
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"hostName": "192.168.1.100",
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"app": "USER-SERVICE", # 服务名称
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"ipAddr": "192.168.1.100", # 实例 IP 地址
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"status": "UP", # 状态
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"overriddenStatus": "UNKNOWN", # 覆盖状态
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"port": {
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"$": 8761, # 端口
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"@enabled": "true" # 开始端口
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},
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"securePort": {
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"$": 443,
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"@enabled": "false"
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},
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"metadata": {
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"management.port": "8761",
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"weight": 100 # 权重，需要通过 spring boot 应用的 eureka.instance.metadata-map.weight 进行配置
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},
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"homePageUrl": "http://192.168.1.100:8761/",
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"statusPageUrl": "http://192.168.1.100:8761/actuator/info",
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"healthCheckUrl": "http://192.168.1.100:8761/actuator/health",
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... ...
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}
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]
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}
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]
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}
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}
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```
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解析 instance 数据步骤：
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1. 首先要选择状态为 “UP” 的实例： overriddenStatus 值不为 "UNKNOWN" 以 overriddenStatus 为准，否则以 status 的值为准；
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2. IP 地址：以 ipAddr 的值为 IP; 并且必须是 IPv4 或 IPv6 格式的；
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3. 端口：端口取值规则是，如果 port["@enabled"] 等于 "true" 那么使用 port["\$"] 的值；如果 securePort["@enabled"] 等于 "true" 那么使用 securePort["$"] 的值；
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4. 权重：权重取值顺序是，先判断 `metadata.weight` 是否有值，如果没有，则取配置中的 `eureka.weight` 的值, 如果还没有，则取默认值`100`；
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这个例子转成 APISIX nodes 的结果如下：
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```json
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[
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{
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"host" : "192.168.1.100",
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"port" : 8761,
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"weight" : 100,
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"metadata" : {
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"management.port": "8761",
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}
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}
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]
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```
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## 注册中心配置
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### 选择注册中心
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首先要在 `conf/config.yaml` 文件中增加如下配置，以选择注册中心的类型：
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```yaml
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apisix:
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discovery: eureka
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```
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此名称要与 `apisix/discovery/` 目录中实现对应注册中心的文件名保持一致。
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现已支持注册中心有：Eureka 。
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### Eureka 的配置
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在 `conf/config.yaml` 增加如下格式的配置：
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```yaml
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eureka:
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host: # it's possible to define multiple eureka hosts addresses of the same eureka cluster.
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- "http://${usename}:${passowrd}@${eureka_host1}:${eureka_port1}"
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- "http://${usename}:${passowrd}@${eureka_host2}:${eureka_port2}"
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prefix: "/eureka/"
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fetch_interval: 30 # 从 eureka 中拉取数据的时间间隔，默认30秒
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weight: 100 # default weight for node
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timeout:
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connect: 2000 # 连接 eureka 的超时时间，默认2000ms
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send: 2000 # 向 eureka 发送数据的超时时间，默认2000ms
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read: 5000 # 从 eureka 读数据的超时时间，默认5000ms
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```
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通过 `eureka.host ` 配置 eureka 的服务器地址。
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如果 eureka 的地址是 `http://127.0.0.1:8761/` ，并且不需要用户名和密码验证的话，配置如下：
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```yaml
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eureka:
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host:
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- "http://127.0.0.1:8761"
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prefix: "/eureka/"
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```
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## upstream 配置
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APISIX是通过 `upstream.service_name` 与注册中心的服务名进行关联。下面是将 uri 为 "/user/*" 的请求路由到注册中心名为 "USER-SERVICE" 的服务上例子：
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```shell
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$ curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -i -d '
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{
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"uri": "/user/*",
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"upstream": {
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"service_name": "USER-SERVICE",
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"type": "roundrobin"
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}
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}'
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HTTP/1.1 201 Created
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Date: Sat, 31 Aug 2019 01:17:15 GMT
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Content-Type: text/plain
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Transfer-Encoding: chunked
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Connection: keep-alive
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Server: APISIX web server
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{"node":{"value":{"uri":"\/user\/*","upstream": {"service_name": "USER-SERVICE", "type": "roundrobin"}},"createdIndex":61925,"key":"\/apisix\/routes\/1","modifiedIndex":61925},"action":"create"}
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```
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因为上游的接口 URL 可能会有冲突，通常会在网关通过前缀来进行区分：
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```shell
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$ curl http://127.0.0.1:9080/apisix/admin/routes/1 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -i -d '
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{
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"uri": "/a/*",
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"plugins": {
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"proxy-rewrite" : {
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regex_uri: ["^/a/(.*)", "/${1}"]
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}
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}
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"upstream": {
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"service_name": "A-SERVICE",
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"type": "roundrobin"
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}
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}'
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$ curl http://127.0.0.1:9080/apisix/admin/routes/2 -H 'X-API-KEY: edd1c9f034335f136f87ad84b625c8f1' -X PUT -i -d '
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{
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"uri": "/b/*",
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"plugins": {
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"proxy-rewrite" : {
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regex_uri: ["^/b/(.*)", "/${1}"]
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}
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}
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"upstream": {
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"service_name": "B-SERVICE",
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"type": "roundrobin"
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}
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}'
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```
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假如 A-SERVICE 和 B-SERVICE 都提供了一个 `/test` 的接口，通过上面的配置，可以通过 `/a/test` 访问 A-SERVICE 的 `/test` 接口，通过 `/b/test` 访问 B-SERVICE 的 `/test` 接口。
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**注意**：配置 `upstream.service_name` 后 `upstream.nodes` 将不再生效，而是使用从注册中心的数据来替换，即使注册中心的数据是空的。
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