redisson-dns-search-domain-unknown-host-exception

문제점

...
Unable to resolve redis-m.xxxxxx.xxx.xx.xxxx.xx
io.netty.resolver.dns.DnsResolveContext$SearchDomainUnknownHostException: Failed to resolve 'redis-m.xxxxxx.xxx.xx.xxxx.xx' and search domain query for configured domains failed as well: [xxx-xxxxxxx, xxxxxxxxx]  
    at io.netty.resolver.dns.DnsResolveContext.finishResolve(DnsResolveContext.java:1047)  
    at io.netty.resolver.dns.DnsResolveContext.tryToFinishResolve(DnsResolveContext.java:1000)  
    at io.netty.resolver.dns.DnsResolveContext.query(DnsResolveContext.java:418)  
    at io.netty.resolver.dns.DnsResolveContext.access$600(DnsResolveContext.java:66)  
    at io.netty.resolver.dns.DnsResolveContext$2.operationComplete(DnsResolveContext.java:467)  
    at io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:578)  
    at io.netty.util.concurrent.DefaultPromise.notifyListeners0(DefaultPromise.java:571)  
    at io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:550)  
    at io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:491)  
    at io.netty.util.concurrent.DefaultPromise.setValue0(DefaultPromise.java:616)  
    at io.netty.util.concurrent.DefaultPromise.setFailure0(DefaultPromise.java:609)  
    at io.netty.util.concurrent.DefaultPromise.tryFailure(DefaultPromise.java:117)  
    at io.netty.resolver.dns.DnsQueryContext.tryFailure(DnsQueryContext.java:256)  
    at io.netty.resolver.dns.DnsQueryContext$4.run(DnsQueryContext.java:208)  
    at io.netty.util.concurrent.PromiseTask.runTask(PromiseTask.java:98)  
    at io.netty.util.concurrent.ScheduledFutureTask.run(ScheduledFutureTask.java:153)  
    at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:174)  
    at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:167)  
    at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:470)  
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:503)  
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)  
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)  
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)  
    at java.base/java.lang.Thread.run(Unknown Source)  
Caused by: io.netty.resolver.dns.DnsNameResolverTimeoutException: [/xx.xxx.x.xx:53] query via UDP timed out after 5000 milliseconds (no stack trace available)
...

  • 간헐적으로 에러 발생

  • 에러 해석

    • redis-host에 대해 DNS로 찾지 못함.

    • Timeout 발생 DNS서버가 5초 내로 응답하지 못함

  • 의존성

    • java 17

    • org.redisson:redisson-spring-boot-starter:3.18.0

      • io.netty:4.1.79 (Final)

    • `org.springframework.boot:2.7.3

원인

  • redisson(netty) -> DNS

    • 기존 DnsAddressResolverGroupFactory 을 통해 생성된 DnsAddressResolverGroup는 여러 DNS에 동시에 쿼리?

      • (추측) 쿼리 중 하나만 실패해도 조회실패이지 않았을까 -> 에러 발생

      • 동작 방식에 대한 확인이 필요

  • SequentialDnsAddressResolverFactory 을 통해 생성된 DnsAddressResolver의 경우

    • DNS 요청에 대한 동시성을 제어했음.

    • 최대 8개 DNS 조회만 발생하도록

    • DNS 요청에 대한 부하를 줄여서 문제가 없는걸까? (좀 더 확인해봐야할 부분)

정리

  • Authoritative

    • 해당 도메인의 공식 DNS 정보 보유

    • 응답이 최종적이고 신뢰할 수 있음

  • Non-Authoritative

    • 캐시된 정보만 보유

    • 다른 서버에 추가 확인 필요할 수 있음

  • NXDOMAIN

    • Non-Existent Domain

    • 도메인이 존재하지 않음을 나타내는 DNS 응답

  • netty issue

    • netty pull request

    • 기존 -> 여러 nameserver 가 존재할 때, 그 중 하나의 nameserver 가 NXDOMAIN (non-existent domain, 도메인이 존재하지 않음) 으로 응답하면 해당 쿼리 자체를 실패 처리

      • authoritative or non-authoritative 상관 없이

    • 개선 -> 만약 NXDOMAIN 이지만 non-authoritative 이라면 다음 nameserver로 쿼리 시도

      • https://github.com/netty/netty/pull/8731/files

해결

  • redisson commit

    • DnsAddressResolverGroupFactory 대신 SequentialDnsAddressResolverFactory 사용하도록 변경

      • DNS 조회에 대한 동시성을 제어함.

  • 즉 3.31.0 버전 이상으로 redisson version upgrade함.

    • io.netty:4.1.79 (Final)

// AS-IS
implementation("org.redisson:redisson-spring-boot-starter:3.18.0")

// TO-BE
implementation("org.redisson:redisson-spring-boot-starter:3.38.1") {
	exclude(group = "org.redisson", module = "redisson-spring-data-33")
}
implementation("org.redisson:redisson-spring-data-27:3.38.1")

  • SpringBoot 2.7 대는 위와와 같이 변경을 권장함.

    • 버전을 올리고,

    • spring-data-33 제외

    • spring-data-27 추가

    • https://redisson.org/docs/integration-with-spring/#spring-boot-starter

참고

  • https://github.com/redisson/redisson/issues/1625

  • https://github.com/redisson/redisson/issues/1944

  • https://github.com/netty/netty/issues/8261#issuecomment-427350547

  • https://github.com/redisson/redisson/commit/2d83ebdf64bde8793b8c3b24be81ad23e72119d5

  • https://zorba91.tistory.com/353

  • https://blog.naver.com/dong6245/140050637164

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