DnsNameResolver should log in trace level if notification of the promise fails (#9022)

Motivation:

During investigating some other bug I noticed that we log with warn level if we fail to notify the promise due the fact that it is already full-filled. This is not correct and missleading as there is nothing wrong with it in general. A promise may already been fullfilled because we did multiple queries and one of these was successful.

Modifications:

- Change log level to trace
- Add unit test which before did log with warn level but now does with trace level.

Result:

Less missleading noise in the log.

resolver-dns/src/main/java/io/netty/resolver/dns/DnsNameResolver.java

@@ -858,13 +858,19 @@ public class DnsNameResolver extends InetNameResolver {
 
     static <T> void trySuccess(Promise<T> promise, T result) {
         if (!promise.trySuccess(result)) {
-            logger.warn("Failed to notify success ({}) to a promise: {}", result, promise);
+            // There is nothing really wrong with not be able to notify the promise as we may have raced here because
+            // of multiple queries that have been executed. Log it with trace level anyway just in case the user
+            // wants to better understand what happened.
+            logger.trace("Failed to notify success ({}) to a promise: {}", result, promise);
         }
     }
 
     private static void tryFailure(Promise<?> promise, Throwable cause) {
         if (!promise.tryFailure(cause)) {
-            logger.warn("Failed to notify failure to a promise: {}", promise, cause);
+            // There is nothing really wrong with not be able to notify the promise as we may have raced here because
+            // of multiple queries that have been executed. Log it with trace level anyway just in case the user
+            // wants to better understand what happened.
+            logger.trace("Failed to notify failure to a promise: {}", promise, cause);
         }
     }
 

resolver-dns/src/test/java/io/netty/resolver/dns/DnsNameResolverTest.java

@@ -2550,4 +2550,31 @@ public class DnsNameResolverTest {
             }
         }
     }
+
+    @Test
+    public void testDropAAAA() throws IOException {
+        String host = "somehost.netty.io";
+        TestDnsServer dnsServer2 = new TestDnsServer(Collections.singleton(host));
+        dnsServer2.start(true);
+        DnsNameResolver resolver = null;
+        try {
+            DnsNameResolverBuilder builder = newResolver()
+                    .recursionDesired(false)
+                    .queryTimeoutMillis(500)
+                    .resolvedAddressTypes(ResolvedAddressTypes.IPV4_PREFERRED)
+                    .maxQueriesPerResolve(16)
+                    .nameServerProvider(new SingletonDnsServerAddressStreamProvider(dnsServer2.localAddress()));
+
+            resolver = builder.build();
+            List<InetAddress> addressList = resolver.resolveAll(host).syncUninterruptibly().getNow();
+            assertEquals(1, addressList.size());
+            assertEquals(host, addressList.get(0).getHostName());
+        } finally {
+            dnsServer2.stop();
+            if (resolver != null) {
+                resolver.close();
+            }
+        }
+    }
+
 }

resolver-dns/src/test/java/io/netty/resolver/dns/TestDnsServer.java

@@ -17,6 +17,7 @@ package io.netty.resolver.dns;
 
 import io.netty.util.NetUtil;
 import org.apache.directory.server.dns.DnsServer;
+import org.apache.directory.server.dns.io.decoder.DnsMessageDecoder;
 import org.apache.directory.server.dns.io.encoder.DnsMessageEncoder;
 import org.apache.directory.server.dns.io.encoder.ResourceRecordEncoder;
 import org.apache.directory.server.dns.messages.DnsMessage;
@@ -27,7 +28,6 @@ import org.apache.directory.server.dns.messages.ResourceRecord;
 import org.apache.directory.server.dns.messages.ResourceRecordImpl;
 import org.apache.directory.server.dns.messages.ResourceRecordModifier;
 import org.apache.directory.server.dns.protocol.DnsProtocolHandler;
-import org.apache.directory.server.dns.protocol.DnsUdpDecoder;
 import org.apache.directory.server.dns.protocol.DnsUdpEncoder;
 import org.apache.directory.server.dns.store.DnsAttribute;
 import org.apache.directory.server.dns.store.RecordStore;
@@ -37,6 +37,8 @@ import org.apache.mina.core.session.IoSession;
 import org.apache.mina.filter.codec.ProtocolCodecFactory;
 import org.apache.mina.filter.codec.ProtocolCodecFilter;
 import org.apache.mina.filter.codec.ProtocolDecoder;
+import org.apache.mina.filter.codec.ProtocolDecoderAdapter;
+import org.apache.mina.filter.codec.ProtocolDecoderOutput;
 import org.apache.mina.filter.codec.ProtocolEncoder;
 import org.apache.mina.filter.codec.ProtocolEncoderOutput;
 import org.apache.mina.transport.socket.DatagramAcceptor;
@@ -83,6 +85,13 @@ class TestDnsServer extends DnsServer {
 
     @Override
     public void start() throws IOException {
+        start(false);
+    }
+
+    /**
+     * Start the {@link TestDnsServer} but drop all {@code AAAA} queries and not send any response to these at all.
+     */
+    public void start(final boolean dropAAAAQueries) throws IOException {
         InetSocketAddress address = new InetSocketAddress(NetUtil.LOCALHOST4, 0);
         UdpTransport transport = new UdpTransport(address.getHostName(), address.getPort());
         setTransports(transport);
@@ -94,7 +103,8 @@ class TestDnsServer extends DnsServer {
             public void sessionCreated(IoSession session) {
                 // USe our own codec to support AAAA testing
                 session.getFilterChain()
-                    .addFirst("codec", new ProtocolCodecFilter(new TestDnsProtocolUdpCodecFactory()));
+                        .addFirst("codec", new ProtocolCodecFilter(
+                                new TestDnsProtocolUdpCodecFactory(dropAAAAQueries)));
             }
         });
 
@@ -142,6 +152,11 @@ class TestDnsServer extends DnsServer {
     private final class TestDnsProtocolUdpCodecFactory implements ProtocolCodecFactory {
         private final DnsMessageEncoder encoder = new DnsMessageEncoder();
         private final TestAAAARecordEncoder recordEncoder = new TestAAAARecordEncoder();
+        private final boolean dropAAAArecords;
+
+        TestDnsProtocolUdpCodecFactory(boolean dropAAAArecords) {
+            this.dropAAAArecords = dropAAAArecords;
+        }
 
         @Override
         public ProtocolEncoder getEncoder(IoSession session) {
@@ -175,7 +190,22 @@ class TestDnsServer extends DnsServer {
 
         @Override
         public ProtocolDecoder getDecoder(IoSession session) {
-            return new DnsUdpDecoder();
+            return new ProtocolDecoderAdapter() {
+                private DnsMessageDecoder decoder = new DnsMessageDecoder();
+
+                @Override
+                public void decode(IoSession session, IoBuffer in, ProtocolDecoderOutput out) throws IOException {
+                    DnsMessage message = decoder.decode(in);
+                    if (dropAAAArecords) {
+                        for (QuestionRecord record: message.getQuestionRecords()) {
+                            if (record.getRecordType() == RecordType.AAAA) {
+                                return;
+                            }
+                        }
+                    }
+                    out.write(message);
+                }
+            };
         }
 
         private final class TestAAAARecordEncoder extends ResourceRecordEncoder {