尋視線上環境日誌時，發現瞭如下錯誤，查了一下，得知可能是eureka服務註冊中心不可用導致的，
不過檢查了一下服務註冊中心項目，發現是正常運行的，且這個錯誤日誌只是偶爾出現，所以就有些困惑了。
排查過程：
1，然後我找到報錯的這個項目的線上環境關於eureka的配置，然後對其可能註冊到的所有eureka註冊中心都一一進行訪問，發現前兩個都是正常可以訪問的，正納悶時，第3個註冊中心的ip與端口發現訪問不了了，這時就略有所悟，應該是無法通過這個註冊中心的地址進行註冊了
2，然後打開eureka註冊中心項目，查看其對外訪問ip與端口，果然只有錯誤日誌項目配置中的前2個ip，第3個ip是沒有的，再次驗證了問題所在。
解決方案：
方案1，可以將客戶端項目中配置的註冊中心ip添加到eureka註冊中心項目對外訪問ip列表中（因爲我的項目該ip機器下線，所以不適合我）
方案2，將客戶端項目中配置的該ip移除（本人採取的這種方案）
當然爲了更高可用，也可以在eureka註冊中心項目中添加新的ip，將客戶端項目中配置更新舊的ip爲新的可用的ip
經驗總結：
客戶端服務配置的eureka註冊中心列表，只要有有個不可用，其它哪怕都可用，也會報如下錯誤，所以儘量及時清楚不可用的註冊中心機器配置
2019-12-06 11:28:02.454 ERROR [DiscoveryClient-HeartbeatExecutor-0] com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient
- Request execution errorcom.sun.jersey.api.client.ClientHandlerException:
java.net.ConnectException: Connection refused (Connection refused)
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187)
at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123)
at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27)
at com.sun.jersey.api.client.Client.handle(Client.java:652)
at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682)
at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74)
at com.sun.jersey.api.client.WebResource$Builder.put(WebResource.java:529)
at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.sendHeartBeat(AbstractJerseyEurekaHttpClient.java:102)
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$3.execute(EurekaHttpClientDecorator.java:92)
at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73)
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.sendHeartBeat(EurekaHttpClientDecorator.java:89)
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$3.execute(EurekaHttpClientDecorator.java:92)
at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.executeOnNewServer(RedirectingEurekaHttpClient.java:118
at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.execute(RedirectingEurekaHttpClient.java:79)
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.sendHeartBeat(EurekaHttpClientDecorator.java:89)
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$3.execute(EurekaHttpClientDecorator.java:92)
at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:119)
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.sendHeartBeat(EurekaHttpClientDecorator.java:89)
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$3.execute(EurekaHttpClientDecorator.java:92)
at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77)
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.sendHeartBeat(EurekaHttpClientDecorator.java:89)
at com.netflix.discovery.DiscoveryClient.renew(DiscoveryClient.java:824)
at com.netflix.discovery.DiscoveryClient$HeartbeatThread.run(DiscoveryClient.java:1393)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748) Caused by: java.net.ConnectException: Connection refused (Connection refused)
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121)
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180)
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144)
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134)
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:610)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:445)
at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173)
... 27 common frames omitted