'Netty is unable to resolve a DNS name

I use Marketo to send emails from my Java application, I submit REST requests to the Marketo API using WebClient. Recently sending emails has started throwing exceptions, and I discovered that Netty is throwing the following error:

Received a mismatching DNS response: DatagramDnsResponse(from: /100.96.1.1:53, to: /0:0:0:0:0:0:0:0:50578, 19016, QUERY(0), NoError(0), RD RA)
        DefaultDnsQuestion(145-jnh-675.mktorest.com. IN A)
        DefaultDnsRawRecord(145-jnh-675.mktorest.com. 91 IN A 4B)

Received a mismatching DNS response: DatagramDnsResponse(from: /100.96.1.1:53, to: /0:0:0:0:0:0:0:0:50578, 24563, QUERY(0), NoError(0), RD RA)
        DefaultDnsQuestion(145-jnh-675.mktorest.com. IN AAAA)
        DefaultDnsRawRecord(mktorest.com. 122 IN SOA 52B)

If I interrogate that DNS name using dig, I get a NOERROR status, so why is Netty throwing this error? The following is the output from dig.

$ dig 145-JNH-675.mktorest.com

; <<>> DiG 9.10.6 <<>> 145-JNH-675.mktorest.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44141
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;145-jnh-675.mktorest.com.  IN  A

;; ANSWER SECTION:
145-jnh-675.mktorest.com. 300   IN  A   199.15.214.159

;; Query time: 96 msec
;; SERVER: 100.96.1.1#53(100.96.1.1)
;; WHEN: Tue Apr 19 17:55:05 EDT 2022
;; MSG SIZE  rcvd: 58
javadnsnetty


Solution 1:[1]

I was able to resolve this changing the default DNS resolver as per a Reactor Netty issue here (https://github.com/reactor/reactor-netty/issues/1431).

final var httpClient = HttpClient.create().resolver(DefaultAddressResolverGroup.INSTANCE)
final var webClient = WebClient.builder().clientConnector(ReactorClientHttpConnector(httpClient)).build()

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Fam

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