【Azure Redis 缓存】Redisson 连接 Azure Redis出现间歇性 java.net.UnknownHostException 异常

问题描述

在Java项目中，使用Redisson作为连接Redis的客户端，间歇性的出现了DNS Monitor throwable 错误。

DNSMonitor throwable="java.net.UnknownHostException: failed to resolve 'xxxxxx.redis.cache.chinacloudapi.cn'

Redisson版本为：

org.redisson:redisson:3.12.0

全部的异常信息为：

level=ERROR logger=org.redisson.connection.DNSMonitor throwable="java.net.UnknownHostException: failed to resolve 'xxxxxx.redis.cache.chinacloudapi.cn' after 2 queries
       at io.netty.resolver.dns.DnsResolveContext.finishResolve(DnsResolveContext.java:901)
       at io.netty.resolver.dns.DnsResolveContext.tryToFinishResolve(DnsResolveContext.java:860)
       at io.netty.resolver.dns.DnsResolveContext.query(DnsResolveContext.java:328)
       at io.netty.resolver.dns.DnsResolveContext.access$600(DnsResolveContext.java:63)
       at io.netty.resolver.dns.DnsResolveContext$2.operationComplete(DnsResolveContext.java:377)
       at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:502)
       at io.netty.util.concurrent.DefaultPromise.notifyListeners0(DefaultPromise.java:495)
       at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:474)
       at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:415)
       at io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:540)
       at io.netty.util.concurrent.DefaultPromise.setFailure0(DefaultPromise.java:533)
       at io.netty.util.concurrent.DefaultPromise.tryFailure(DefaultPromise.java:114)
       at io.netty.resolver.dns.DnsQueryContext.setFailure(DnsQueryContext.java:220)
       at io.netty.resolver.dns.DnsQueryContext.access$300(DnsQueryContext.java:43)
       at io.netty.resolver.dns.DnsQueryContext$4.run(DnsQueryContext.java:170)
       at io.netty.util.concurrent.PromiseTask$RunnableAdapter.call(PromiseTask.java:38)
       at io.netty.util.concurrent.ScheduledFutureTask.run(ScheduledFutureTask.java:127)
       at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163)
       at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:405)
       at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:500)
       at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:906)
       at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
       at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
       at java.lang.Thread.run(Thread.java:748)
Caused by: io.netty.resolver.dns.DnsNameResolverTimeoutException: [/8.8.4.4:53] query timed out after 5000 milliseconds (no stack trace available)
" thread=redisson-netty-4-21 message="Unable to resolve xxxxxx.redis.cache.chinacloudapi.cn" fluentd=517d053c90c2 tag=logback.aliClient.10.218.192.150

问题分析

根据错误提示，在Github上找到 Redisson 和 Netty 都存在相似的问题。最后都建议升级 Redisson 版本到最新，同时也把 Netty 的版本升级到最新。

Regression: DNS resolver failing to find valid DNS record ：https://github.com/redisson/redisson/issues/1625

DNS resolver failing to find valid DNS record ： https://github.com/netty/netty/issues/8261

如果升级比较复杂的话，也可以将redisson的dnsMonitoringInterval参数设置为-1。

参考资料

Regression: DNS resolver failing to find valid DNS record : https://github.com/redisson/redisson/issues/1625

DNS resolver failing to find valid DNS record ： https://github.com/netty/netty/issues/8261

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