DNS Error in Logs Using Elasticity

Question

I get this strange error for a week, here is the stack trace

 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)

An application is the springboot API, using the redisson client to connect to the elastic. Although I see these errors, the API works fine, without errors. Failed to get any information about this online either. Has anyone else come across something similar?

I also log this error, followed by the error above

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)

Adding Additional Logs

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]

Answer 1

The magazine is already giving a hint Unable to resolve redis.***********.cache.amazonaws.com.

First try to check if your instance can resolve (find where the Redis server is), you can do this simply:

$ host redis.****.cache.amazonaws.com

ping redis.****.cache.amazonaws.com , ( IP-)

, , , , DNS-. ,

$ dig @8.8.8.8 redis.***cache.amazonaws.com +short

DNS Google, , , /etc/resolv.conf

, , /redis , - :

redis-cli -h redis.***.cache.amazonaws.com

, 6379,

redis-cli -h redis.***.cache.amazonaws.com -p XXXX 

, XXXX .

redis-cli, telnet, :

telnet redis.***.cache.amazonaws.com 6379

, , , AWS, , .