ServiceComb 开发实战（1） —— Service-Center 安装部署

一. Service-Center 是什么

Service-Center（SC）是一个服务注册中心。 服务提供者（provider）可以将自身的实例信息注册到 SC，以供服务消费者（consumer）从 SC 发现并使用它。
在传统服务中，一般将 provider 的实例信息配置到指定的配置文件中，以供 consumer 使用。这种使用方式下，若 provider 修改了配置信息，counsumer 则需要手工修改配置，并重启服务来适应变化。若是需要维护的服务较少，这倒不会花费太多气力。然而在微服务领域，涉及的服务数动辄成百上千，若是通过手工去维护这些配置，相信运维人员早就磨刀霍霍向开发了。服务注册中心应运而生。

二. 设计原理

参见：ServiceComb官网 ServiceCenter用户手册，此处不再赘述

三. 安装与启动

1. 官方安装包

官网获取指定版本并下载：http://servicecomb.apache.org/cn/release/
笔者在此处使用了 apache-servicecomb-incubating-service-center-1.0.0-linux-amd64.tar.gz 包，实际操作时请根据系统环境选取对应版本

# 下载linux版本包
$ wget http://archive.apache.org/dist/incubator/servicecomb/incubator-servicecomb-service-center/1.0.0/apache-servicecomb-incubating-service-center-1.0.0-linux-amd64.tar.gz

# 解压tar包
$ tar -zxvf  apache-servicecomb-incubating-service-center-1.0.0-linux-amd64.tar.gz

# 启动servicecenter服务
$ cd apache-servicecomb-incubating-service-center-1.0.0-linux-amd64/
$ ./start-service-center.sh
$ ps -ef | grep service-center
root     27048     1  2 14:38 pts/2    00:00:00 ./service-center
root     27164 22742  0 14:38 pts/2    00:00:00 grep --color=auto service-center

# 查看监听配置
$ cat conf/app.conf | grep "sever options" -A 16
# sever options
###################################################################
# if you want to listen at ipv6 address, then set the httpaddr value like:
# httpaddr = 2400:A480:AAAA:200::159        (global scope)
# httpaddr = fe80::f816:3eff:fe17:c38b%eth0 (link-local scope)
httpaddr = 127.0.0.1
httpport = 30100

read_header_timeout = 60s
read_timeout = 60s
idle_timeout = 60s
write_timeout = 60s
max_header_bytes = 32768 # 32K
max_body_bytes = 2097152 # 2M

enable_pprof = 0

# 查看端口监听
$ netstat -apn | grep :30100
tcp        0      0 127.0.0.1:30100         0.0.0.0:*               LISTEN      27048/service-cente

$ curl http://127.0.0.1:30100
{"_links":{"pb:latest-pact-versions":{"href":"http://127.0.0.1:30100/pacts/latest","title":"Latest pact versions"},"pb:latest-provider-pacts":{"href":"http://127.0.0.1:30100/pacts/provider/{provider}/latest","title":"Latest pacts by provider","templated":true},"pb:latest-provider-pacts-with-tag":{"href":"http://127.0.0.1:30100/pacts/provider/{provider}/latest/{tag}","title":"Latest pacts by provider with a specified tag","templated":true},"pb:pacticipants":{"href":"http://127.0.0.1:30100/participants","title":"Pacticipants"},"pb:publish-pact":{"href":"http://127.0.0.1:30100/pacts/provider/{provider}/consumer/{consumer}/version/{consumerApplicationVersion}","title":"Publish a pact","templated":true},"pb:webhooks":{"href":"http://127.0.0.1:30100/webhooks","title":"Webhooks"},"self":{"href":"http://127.0.0.1:30100/","title":"Index"}},"curies":[{"href":"http://127.0.0.1:30100/doc/{rel}","name":"pb"}]}

至此，service-center服务已成功启动，其监听地址为： 127.0.0.1:30100

2. github 源码安装

gihub官方代码库：https://github.com/apache/servicecomb-service-center
注：源码安装时涉及 golang.org/x/… 等包的下载，若因"墙"无法下载的，可以通过设置 goproxy解决

goproxy 设置：

$ echo "export GOPROXY=https://goproxy.io" >> /etc/profile
$ source /etc/profile

安装启动：

# 源码下载
$ git clone https://github.com/apache/servicecomb-service-center.git $GOPATH/src/github.com/apache/servicecomb-service-center
Cloning into '/root/chan/go//src/github.com/apache/servicecomb-service-center'...
remote: Enumerating objects: 224, done.
remote: Counting objects: 100% (224/224), done.
remote: Compressing objects: 100% (155/155), done.
remote: Total 18042 (delta 111), reused 120 (delta 66), pack-reused 17818
Receiving objects: 100% (18042/18042), 16.05 MiB | 1.51 MiB/s, done.
Resolving deltas: 100% (9863/9863), done.
Checking connectivity... done.
$ cd $GOPATH/src/github.com/apache/servicecomb-service-center

# 查看并确保 go 版本到 1.11+
$ go version
go version go1.11.4 linux/amd64

# 源码编译
$ GO111MODULE=on go mod download
go: finding github.com/dgrijalva/jwt-go v3.2.0+incompatible
go: finding github.com/coreos/pkg v0.0.0-20180108230652-97fdf19511ea
...
go: finding k8s.io/client-go v2.0.0-alpha.0.0.20180817174322-745ca8300397+incompatible

$ GO111MODULE=on go mod vendor
$ go build -o service-center

# 安装并启动 etcd
$ wget https://github.com/coreos/etcd/releases/download/v3.1.8/etcd-v3.1.8-linux-amd64.tar.gz
$ tar -xvf etcd-v3.1.8-linux-amd64.tar.gz
$ cd etcd-v3.1.8-linux-amd64
$ ./etcd

# 配置并启动 service-center
$ cd $GOPATH/src/github.com/apache/servicecomb-service-center
$ cp -r ./etc/conf .
$ ./service-center

# 查看端口监听
$ cat conf/app.conf | grep "sever options" -A 16
# sever options
###################################################################
# if you want to listen at ipv6 address, then set the httpaddr value like:
# httpaddr = 2400:A480:AAAA:200::159        (global scope)
# httpaddr = fe80::f816:3eff:fe17:c38b%eth0 (link-local scope)
httpaddr = 127.0.0.1
httpport = 30100

read_header_timeout = 60s
read_timeout = 60s
idle_timeout = 60s
write_timeout = 60s
max_header_bytes = 32768 # 32K
max_body_bytes = 2097152 # 2M

enable_pprof = 0

3. docker 镜像

此处将从 docker 和 kubernetes 两个方向，对service-center容器的启动进行介绍
由于文章仅做 service-center 研究，涉及 docker、kubernetes 知识还请各位自行补充
注：docker 拉取镜像时，若涉及国外镜像无法下载，可以通过设置 docker registry-mirror进行解决

docker registry-mirror 设置：

$ cat <<EOF > /etc/docker/daemon.json
{
"registry-mirrors": ["https://registry.docker-cn.com"]
}
EOF

$ sudo systemctl daemon-reload
$ sudo systemctl start docker

docker 镜像运行：

# 下载镜像
$ docker pull servicecomb/service-center
Using default tag: latest
latest: Pulling from servicecomb/service-center
Digest: sha256:d1c74d569dc4ca09649add02aab16758325a5b0945b0029bd70f446e6db112b4
Status: Downloaded newer image for servicecomb/service-center:latest
# 启动容器
$ docker run -d -p 30100:30100 servicecomb/service-center
0733021cd96d466f7eb27e482c9dbe75b980aad1bac0490e9b5ed65bd5329e0b

# 查看端口监听
$ docker ps | grep service-center
0733021cd96d        servicecomb/service-center        "/opt/service-cent..."   3 minutes ago       Up 3 minutes        0.0.0.0:30100->30100/tcp        gallant_varahamihira 

$ curl http://127.0.0.1:30100
{"_links":{"pb:latest-pact-versions":{"href":"http://127.0.0.1:30100/pacts/latest","title":"Latest pact versions"},"pb:latest-provider-pacts":{"href":"http://127.0.0.1:30100/pacts/provider/{provider}/latest","title":"Latest pacts by provider","templated":true},"pb:latest-provider-pacts-with-tag":{"href":"http://127.0.0.1:30100/pacts/provider/{provider}/latest/{tag}","title":"Latest pacts by provider with a specified tag","templated":true},"pb:pacticipants":{"href":"http://127.0.0.1:30100/participants","title":"Pacticipants"},"pb:publish-pact":{"href":"http://127.0.0.1:30100/pacts/provider/{provider}/consumer/{consumer}/version/{consumerApplicationVersion}","title":"Publish a pact","templated":true},"pb:webhooks":{"href":"http://127.0.0.1:30100/webhooks","title":"Webhooks"},"self":{"href":"http://127.0.0.1:30100/","title":"Index"}},"curies":[{"href":"http://127.0.0.1:30100/doc/{rel}","name":"pb"}]}

容器已启动并监听 127.0.0.1:30100 成功

4. kubernetes 部署

# 配置 kubernetes 资源文件
$ cat <<EOF >> ./service-center.yaml
apiVersion: v1
kind: Service
metadata:
  name: servicecenter
  labels:
    app: servicecenter
spec:
  ports:
  - port: 30100
    name: http
  selector:
    app: servicecenter
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: servicecenter
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: servicecenter
        version: v1
    spec:
      containers:
      - name: servicecenter
        image: servicecomb/service-center:latest
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 30100 
EOF

# 创建 namespace "servicecomb"
$ kubectl create namespace servicecomb
namespace/servicecomb created

# 部署 service-center
$ kubectl -n servicecomb create -f service-center.yaml
service/servicecenter created
deployment.extensions/servicecenter created

# 查看 pod 启动状态
$ kubectl -n servicecomb get pod
NAME                             READY   STATUS    RESTARTS   AGE
servicecenter-7d964b7644-h6f4s   1/1     Running   0          72s

# 获取 service 监听
$ kubectl -n servicecomb get service
NAME            TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)     AGE
servicecenter   ClusterIP   10.104.241.163   <none>        30100/TCP   118s

$ curl http://10.104.241.163:30100
{"_links":{"pb:latest-pact-versions":{"href":"http://10.104.241.163:30100/pacts/latest","title":"Latest pact versions"},"pb:latest-provider-pacts":{"href":"http://10.104.241.163:30100/pacts/provider/{provider}/latest","title":"Latest pacts by provider","templated":true},"pb:latest-provider-pacts-with-tag":{"href":"http://10.104.241.163:30100/pacts/provider/{provider}/latest/{tag}","title":"Latest pacts by provider with a specified tag","templated":true},"pb:pacticipants":{"href":"http://10.104.241.163:30100/participants","title":"Pacticipants"},"pb:publish-pact":{"href":"http://10.104.241.163:30100/pacts/provider/{provider}/consumer/{consumer}/version/{consumerApplicationVersion}","title":"Publish a pact","templated":true},"pb:webhooks":{"href":"http://10.104.241.163:30100/webhooks","title":"Webhooks"},"self":{"href":"http://10.104.241.163:30100/","title":"Index"}},"curies":[{"href":"http://10.104.241.163:30100/doc/{rel}","name":"pb"}]}

在 kubernetes 中部署 service-center 成功，其监听地址被分配到了 10.104.241.163:30100

四. 服务注册与发现初窥

以下将通过 curl 命令模拟 Service-center 中的服务注册与发现，以便于了解其流程。具体的示例与源码分析将在后续的文章中展现。

1. provider 服务注册

   $ curl -X POST \
   http://127.0.0.1:30100/registry/v3/microservices \
   -H 'content-type: application/json' \
   -H 'x-domain-name: default' \
   -d '{
     "service":
     {
       "appId": "default",
       "serviceName": "ProviderDemoService",
       "version":"1.0.0"
     }
   }'
   {"serviceId":"fa82132706a6b75a13393d8cf48800f9689b2603"}
   

2. provider 实例注册
   根据上一步返回的的 serviceId，注册微服务实例

   $ curl -X POST \
   http://127.0.0.1:30100/registry/v3/microservices/fa82132706a6b75a13393d8cf48800f9689b2603/instances \
   -H 'content-type: application/json' \
   -H 'x-domain-name: default' \
   -d '{
     "instance": 
     {
         "hostName":"provider-demo",
         "endpoints": [
             "rest://127.0.0.1:8080"
         ]
     }
   }'
   {"instanceId":"6e160fb0196e11e9b8b50242ac110005"}
   

3. consumer 服务注册

   $ curl -X POST \
   http://127.0.0.1:30100/registry/v3/microservices \
   -H 'content-type: application/json' \
   -H 'x-domain-name: default' \
   -d '{
     "service":
     {
       "appId": "default",
       "serviceName": "ConsumerDemoService",
       "version":"1.0.0"
     }
   }'
   {"serviceId":"d08d29edbeaa372c5be88407aa9adb00b4cb6099"}
   

4. 服务发现
   根据 provider 服务名称和版本规则、以及 consumer 服务 ID 进行 provider 服务实例发现

   $ curl -X GET \
   'http://127.0.0.1:30100/registry/v3/instances?appId=default&serviceName=ProviderDemoService&version=latest' \
   -H 'content-type: application/json' \
   -H 'x-consumerid: d08d29edbeaa372c5be88407aa9adb00b4cb6099' \
   -H 'x-domain-name: default'
   {
     "instances": [
       {
         "instanceId": "c23da577197111e9b8b50242ac110005",
         "serviceId": "fa82132706a6b75a13393d8cf48800f9689b2603",
         "endpoints": [
           "rest://127.0.0.1:8080"
         ],
         "hostName": "provider-demo",
         "status": "UP",
         "healthCheck": {
           "mode": "push",
           "interval": 30,
           "times": 3
         },
         "timestamp": "1547631199",
         "modTimestamp": "1547631199",
         "version": "1.0.0"
       }
     ]
   }
   

注：Provider 服务在 30 秒内未向 Service-Center 发送心跳，将会被下线。所以服务发现的请求应在 Provider 服务创建实例后 30 秒内发出才会成功发现实例