spring boot集成dubbo項目啟動過程中報錯，錯誤信息如下：
2020-01-19 17:42:30.466 ERROR - [main] org.springframework.boot.SpringApplication.reportFailure(822) | Application run failed
java.lang.IllegalStateException: zookeeper not connected
at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperClient.<init>(CuratorZookeeperClient.java:83)
at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperTransporter.createZookeeperClient(CuratorZookeeperTransporter.java:26)
at org.apache.dubbo.remoting.zookeeper.support.AbstractZookeeperTransporter.connect(AbstractZookeeperTransporter.java:68)
at org.apache.dubbo.remoting.zookeeper.ZookeeperTransporter$Adaptive.connect(ZookeeperTransporter$Adaptive.java)
at org.apache.dubbo.configcenter.support.zookeeper.ZookeeperDynamicConfiguration.<init>(ZookeeperDynamicConfiguration.java:70)
at org.apache.dubbo.configcenter.support.zookeeper.ZookeeperDynamicConfigurationFactory.createDynamicConfiguration(ZookeeperDynamicConfigurationFactory.java:37)
at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory.lambda$getDynamicConfiguration$0(AbstractDynamicConfigurationFactory.java:39)
at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1660)
at org.apache.dubbo.common.config.configcenter.AbstractDynamicConfigurationFactory.getDynamicConfiguration(AbstractDynamicConfigurationFactory.java:39)
at org.apache.dubbo.common.config.configcenter.DynamicConfiguration.getDynamicConfiguration(DynamicConfiguration.java:223)
at org.apache.dubbo.config.bootstrap.DubboBootstrap.prepareEnvironment(DubboBootstrap.java:815)
at org.apache.dubbo.config.bootstrap.DubboBootstrap.startConfigCenter(DubboBootstrap.java:560)
at org.apache.dubbo.config.bootstrap.DubboBootstrap.useRegistryAsConfigCenterIfNecessary(DubboBootstrap.java:624)
at org.apache.dubbo.config.bootstrap.DubboBootstrap.initialize(DubboBootstrap.java:508)
at org.apache.dubbo.config.bootstrap.DubboBootstrap.start(DubboBootstrap.java:698)
at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onContextRefreshedEvent(DubboBootstrapApplicationListener.java:52)
at org.apache.dubbo.config.spring.context.DubboBootstrapApplicationListener.onApplicationContextEvent(DubboBootstrapApplicationListener.java:45)
at org.apache.dubbo.config.spring.context.OneTimeExecutionApplicationContextEventListener.onApplicationEvent(OneTimeExecutionApplicationContextEventListener.java:40)
at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:172)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:165)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:402)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:359)
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:896)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:552)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:743)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:390)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:312)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1214)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1203)
at cn.mogutrip.base.foundation.shell.Application.main(Application.java:28)
Caused by: java.lang.IllegalStateException: zookeeper not connected
at org.apache.dubbo.remoting.zookeeper.curator.CuratorZookeeperClient.<init>(CuratorZookeeperClient.java:80)
... 30 common frames omitted
項目中引用的是dubbo-spring-boot-starter，版本配置如下：
<dependency>
<groupId>org.apache.dubbo</groupId>
<artifactId>dubbo-spring-boot-starter</artifactId>
<version>2.7.5</version>
</dependency>
從啟動結果可以看出，dubbo的注冊中心zookeeper連接不上了，起初我以為apollo中配置的zookeeper地址錯了，核對了一遍沒毛病。然后看了下項目中的application.properties配置文件，又看了下啟動日志，排除了apollo沒生效的可能性。而且項目中使用的Elastic-Job的配置中心zookeeper和dubbo的一樣，但是Elastic-Job卻啟動成功了。伴隨了一頭霧水，習慣性的百度了下spring boot集成dubbo所遇到的坑，大多數的情況是啟動類上沒有添加 @EnableDubboConfig 注解，可是我的項目添加了的。嘗試了網上的各種坑之后，還是沒有解決。然后我讓組員在他電腦上啟動項目看一下，居然一點問題都沒有。那就是服務器zookeeper不穩定嘍！
可是怎么解決這個不穩定呢？從出錯的問題更了下源碼：
可以發現配置的信息都讀取到了的，走到下面這一步：
boolean connected = client.blockUntilConnected(timeout, TimeUnit.MILLISECONDS);
返回的值是false。如果timeout的值變大，是不是就可能為true了呢？上面一步看出timeout=3000。那么timeout哪里來的，我沒發現我的配置里有3000。
不斷跟進、跟進、跟進：
到了DubboBootstrap類的startConfigCenter方法，已經沒有入參了，這里拿到的timeout也是3000，那就只有下面這行代碼可以取到：
Collection<ConfigCenterConfig> configCenters = configManager.getConfigCenters();
繼續追蹤：
終於看到ConfigCenterConfig類中初始化了timeout = 3000L。原來dubbo的config-center配置中心，默認的獲取配置的超時時間是3秒鍾。
在項目的配置文件中修改一下這個時間為10秒：
dubbo.config-center.timeout=10000
再次啟動項目，完美解決！
總結：遇到問題，還是要從錯誤的本質出發，多跟進底層源碼，加深理解的同時，也學到了其架構思想和perfect的設計。
更多config-center的配置可以參考鏈接：http://dubbo.apache.org/zh-cn/docs/user/references/xml/dubbo-config-center.html