一句话

用agent更优雅，适合agent遍布每个应用机的情况。用catalog更直接，操作更方便

前言

今天遇到写一个服务启动自注册的逻辑时产生了一点纠结，可以使用agent对象的register方法进行注册，也可以使用catalog的register方法进行注册。那么，两种方式有什么区别呢？

agent对象

new 一个consulClient对象,应当是作为一个软consul agent

对API URL对应的节点的属性没有要求. 其可以是server身份也可以是纯agent身份

数据要经过冲突确认后，再存入catalog中

反注册时只可以反注册自身的节点(主机)上的服务,注册时可以注册其他主机上的服务

catalog

connect to consul database

连接的节点应当是server节点

操作后数据立马生效

反注册对所有节点生效

用途

编写反注册节点的服务应使用catalog的方法

使用agent方法反注册服务时，需要指定一个serviceID参数，该ID是的唯一维度是node也就是主机唯一的。因此从catalog进行反注册时最好是提供主机名和服务ID，当然也可以是IP和服务ID，服务名和服务ID的结合我没有尝试过。

案例

实现反注册节点的逻辑

用途：删除已经失效的主机信息，用于取消报警触发

// 根据IP删除节点

func (c *ConsulHelper) DropNodeByIP(ip string) error {

// STEP1: 查找IP在Consul中对应的NodeName

nodeName, err := c.FindNodeNameByIP(ip)

if err != nil {

return err

}

p.Infof("Find node %s by ip %s success, ", nodeName, ip)

// STEP2: 调用DropNode删除节点

err = c.DropNode(nodeName)

if err != nil {

p.Errorf("Drop Node by ip: %s failed, %+v", ip, err)

return err

}

return nil

}

func (c *ConsulHelper) DropNode(nodeName string) error {

var bom = consul.CatalogDeregistration{

Node: nodeName,

Datacenter: common.CONF.Consul.DataCenter,

}

_, err := c.API.Catalog().Deregister(&bom, nil)

return err

}

func (c *ConsulHelper) DropSelfNode() error {

return c.DropNode(c.hostUniqueName)

}

实现反注册服务的逻辑

用途：服务启动时向consul注册自身，服务正常关闭时将自身从consul中反注册

```c#

///

/// 反注册服务(使用catalog实现)

///

///

///

///

public WriteResult DeregisterService(string nodeIP, string serviceID)

{

this.logger.LogDebug($"Now start DeregisterService in {nodeIP}, service:{serviceID}");

var x = new CatalogDeregistration { Datacenter = "dc1", Address = nodeIP, ServiceID= serviceID };

return this.consul.Catalog.Deregister(x).Result;

}

///

/// 注册服务(使用Agent实现)

///

///

public void RegisterService(AgentServiceRegistration serviceRegistration)

{

this.logger.LogDebug("Now do service register");

this.consul.Agent.ServiceRegister(serviceRegistration);

}

///

/// 反注册本机上的服务(使用Agent实现)

///

/// 本机唯一的服务ID

public void DeregisterSelfNodeService(string serviceID)

{

this.logger.LogDebug("Now do service deregister");

this.consul.Agent.ServiceDeregister(serviceID);

}

private void OnStarted(IConsulService consulService)

{

var exposedHTTPURL = this.Configuration["Kestrel:EndPoints:Http:Url"];

var stringPort = exposedHTTPURL.Split(":")[^1];

consulService.RegisterSelfProject(int.Parse(stringPort));

}

private void OnStopped(IConsulService consulService)

{

var exposedHTTPURL = this.Configuration["Kestrel:EndPoints:Http:Url"];

var stringPort = exposedHTTPURL.Split(":")[^1];

consulService.DeregisterSelfProject(int.Parse(stringPort));

}

输出：

```bash

2020/04/23 17:59:26 [WARN] agent: Node name "PsyDuck.local" will not be discoverable via DNS due to invalid characters. Valid characters include all alpha-numerics and dashes.

2020/04/23 17:59:26 [INFO] raft: Restored from snapshot 13-163854-1558515302742

2020/04/23 17:59:26 [INFO] raft: Initial configuration (index=1): [{Suffrage:Voter ID:e15ef033-ec5c-f2c5-4679-43fdfa69f508 Address:10.100.100.1:8300}]

2020/04/23 17:59:26 [INFO] raft: Node at 127.0.0.1:8300 [Follower] entering Follower state (Leader: "")

2020/04/23 17:59:26 [INFO] serf: EventMemberJoin: PsyDuck.local.dc1 127.0.0.1

2020/04/23 17:59:26 [WARN] serf: Failed to re-join any previously known node

2020/04/23 17:59:26 [INFO] serf: EventMemberJoin: PsyDuck.local 127.0.0.1

2020/04/23 17:59:26 [WARN] serf: Failed to re-join any previously known node

2020/04/23 17:59:26 [INFO] consul: Adding LAN server PsyDuck.local (Addr: tcp/127.0.0.1:8300) (DC: dc1)

2020/04/23 17:59:26 [INFO] consul: Handled member-join event for server "PsyDuck.local.dc1" in area "wan"

2020/04/23 17:59:26 [INFO] agent: Started DNS server 0.0.0.0:8600 (tcp)

2020/04/23 17:59:26 [INFO] agent: Started DNS server 0.0.0.0:8600 (udp)

2020/04/23 17:59:26 [INFO] agent: Started HTTP server on [::]:8500 (tcp)

2020/04/23 17:59:26 [INFO] agent: started state syncer

2020/04/23 17:59:33 [ERR] agent: failed to sync remote state: No cluster leader

2020/04/23 17:59:35 [WARN] raft: Heartbeat timeout from "" reached, starting election

2020/04/23 17:59:35 [INFO] raft: Node at 127.0.0.1:8300 [Candidate] entering Candidate state in term 14

2020/04/23 17:59:35 [INFO] raft: Election won. Tally: 1

2020/04/23 17:59:35 [INFO] raft: Node at 127.0.0.1:8300 [Leader] entering Leader state

2020/04/23 17:59:35 [INFO] consul: cluster leadership acquired

2020/04/23 17:59:35 [INFO] consul: New leader elected: PsyDuck.local

2020/04/23 17:59:35 [INFO] consul: member 'PsyDuck.local' joined, marking health alive

2020/04/23 17:59:36 [INFO] agent: Synced node info

==> Failed to check for updates: Get https://checkpoint-api.hashicorp.com/v1/check/consul?arch=amd64&os=darwin&signature=01a8a19a-0919-6b96-8aa1-eaf5f977a351&version=1.4.2: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

2020/04/23 18:00:05 [WARN] agent: Service name "监控系统" will not be discoverable via DNS due to invalid characters. Valid characters include all alpha-numerics and dashes.

2020/04/23 18:00:05 [INFO] agent: Synced service "监控系统@127.0.0.1:5007"

2020/04/23 18:00:29 [INFO] agent: Deregistered service "监控系统@127.0.0.1:5007"

2020/04/23 18:02:06 [INFO] agent: Synced service "DBAMonitorAPI@127.0.0.1:5007"