title: DNS error in logs using elasticache
body: <p>I have been getting this strange error since a week now, here is the stack trace</p>
  
  <pre><code> ERROR (redisson-netty-1-4) [DNSMonitor(operationComplete:98)] Unable to resolve redis.***********.cache.amazonaws.com java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
  
  at java.util.ArrayList.rangeCheck(ArrayList.java:653)
  at java.util.ArrayList.get(ArrayList.java:429)
  at io.netty.resolver.dns.DnsNameResolver.doResolveCached(DnsNameResolver.java:613)
  at io.netty.resolver.dns.DnsNameResolver.doResolve(DnsNameResolver.java:593)
  at io.netty.resolver.dns.DnsNameResolver.doResolve(DnsNameResolver.java:527)
  at io.netty.resolver.SimpleNameResolver.resolve(SimpleNameResolver.java:63)
  </code></pre>
  
  <p>The application is a springboot API using redisson client to connect to elasticache. Though i see these errors, the API is running fine without any errors. Haven't been able to get any clues about this online too. Anyone else here faced something similar?</p>
  
  <p>I also this error in logs followed by the above error </p>
  
  <pre><code>org.redisson.client.RedisTimeoutException: Redis server response timeout (3000 ms) occured for command: (HGET) with params: [packagesCache, PooledUnsafeDirectByteBuf(ridx: 0, widx: 3, cap: 256)] channel: [id: 0xdfd44ac3, L:/10.0.2.206:42857 - R:redis.kl3ise.0001.use1.cache.amazonaws.com/10.0.1.234:6379]
      at org.redisson.command.CommandAsyncService$11.run(CommandAsyncService.java:682)
      at io.netty.util.HashedWheelTimer$HashedWheelTimeout.expire(HashedWheelTimer.java:663)
      at io.netty.util.HashedWheelTimer$HashedWheelBucket.expireTimeouts(HashedWheelTimer.java:738)
      at io.netty.util.HashedWheelTimer$Worker.run(HashedWheelTimer.java:466)
      at java.lang.Thread.run(Thread.java:748)
  </code></pre>
  
  <p>Adding additional logs </p>
  
  <pre><code>Request for schedule for student with access key ab947-cf32-4965-ab06-36d4e904899don date 2018-02-14org.redisson.client.RedisTimeoutException: Redis server response timeout (60000 ms) occured for command: (HEXISTS) with params: [analyzedStudyPlanCache, PooledUnsafeDirectByteBuf(ridx: 0, widx: 9, cap: 256)] channel: [id: 0xe4dc90da, L:/10.0.2.206:56685 – R:redis.kl3ise.0001.use1.cache.amazonaws.com/10.0.1.234:6379]
  </code></pre>