The DnsClient does not have a close method to release the underlying …

…networking resources.

Add a close method to the client that closes the datagram channel, inflight queries are failed.

src/main/asciidoc/dns.adoc

@@ -26,6 +26,8 @@ for non blocking address resolution.
 {@link examples.DNSExamples#example1__}
 ----
 
+A client uses a single event loop for querying purposes, it can safely be used from any thread, including non Vert.x thread.
+
 === lookup
 
 Try to lookup the A (ipv4) or AAAA (ipv6) record for a given name. The first which is returned will be used,

src/main/java/io/vertx/core/dns/DnsClient.java

@@ -24,6 +24,8 @@
  * Provides a way to asynchronously lookup information from DNS servers.
  * <p>
  * Please consult the documentation for more information on DNS clients.
+ * <p>
+ * The client is thread safe and can be used from any thread.
  *
  * @author <a href="mailto:nmaurer@redhat.com">Norman Maurer</a>
  */
@@ -237,4 +239,15 @@ public interface DnsClient {
    * Like {@link #reverseLookup(String, Handler)} but returns a {@code Future} of the asynchronous result
    */
   Future<@Nullable String> reverseLookup(String ipaddress);
+
+  /**
+   * Close the client.
+   */
+  void close(Handler<AsyncResult<Void>> handler);
+
+  /**
+   * Like {@link #close(Handler)} but returns a {@code Future} of the asynchronous result
+   */
+  Future<Void> close();
+
 }

src/main/java/io/vertx/core/dns/impl/DnsClientImpl.java

@@ -27,6 +27,7 @@
 import io.vertx.core.impl.future.PromiseInternal;
 import io.vertx.core.impl.VertxInternal;
 import io.vertx.core.buffer.impl.PartialPooledByteBufAllocator;
+import io.vertx.core.net.impl.ConnectionBase;
 import io.vertx.core.spi.transport.Transport;
 
 import java.net.Inet4Address;
@@ -49,40 +50,39 @@ public final class DnsClientImpl implements DnsClient {
   private final VertxInternal vertx;
   private final LongObjectMap<Query> inProgressMap = new LongObjectHashMap<>();
   private final InetSocketAddress dnsServer;
-  private final ContextInternal actualCtx;
+  private final ContextInternal context;
   private final DatagramChannel channel;
   private final DnsClientOptions options;
+  private volatile Future<Void> closed;
 
   public DnsClientImpl(VertxInternal vertx, DnsClientOptions options) {
     Objects.requireNonNull(options, "no null options accepted");
     Objects.requireNonNull(options.getHost(), "no null host accepted");
 
     this.options = new DnsClientOptions(options);
 
-    ContextInternal creatingContext = vertx.getContext();
-
     this.dnsServer = new InetSocketAddress(options.getHost(), options.getPort());
     if (this.dnsServer.isUnresolved()) {
       throw new IllegalArgumentException("Cannot resolve the host to a valid ip address");
     }
     this.vertx = vertx;
 
     Transport transport = vertx.transport();
-    actualCtx = vertx.getOrCreateContext();
+    context = vertx.getOrCreateContext();
     channel = transport.datagramChannel(this.dnsServer.getAddress() instanceof Inet4Address ? InternetProtocolFamily.IPv4 : InternetProtocolFamily.IPv6);
     channel.config().setOption(ChannelOption.DATAGRAM_CHANNEL_ACTIVE_ON_REGISTRATION, true);
     MaxMessagesRecvByteBufAllocator bufAllocator = channel.config().getRecvByteBufAllocator();
     bufAllocator.maxMessagesPerRead(1);
     channel.config().setAllocator(PartialPooledByteBufAllocator.INSTANCE);
-    actualCtx.nettyEventLoop().register(channel);
+    context.nettyEventLoop().register(channel);
     if (options.getLogActivity()) {
       channel.pipeline().addLast("logging", new LoggingHandler(options.getActivityLogFormat()));
     }
     channel.pipeline().addLast(new DatagramDnsQueryEncoder());
     channel.pipeline().addLast(new DatagramDnsResponseDecoder());
     channel.pipeline().addLast(new SimpleChannelInboundHandler<DnsResponse>() {
       @Override
-      protected void channelRead0(ChannelHandlerContext ctx, DnsResponse msg) throws Exception {
+      protected void channelRead0(ChannelHandlerContext ctx, DnsResponse msg) {
         DefaultDnsQuestion question = msg.recordAt(DnsSection.QUESTION);
         Query query = inProgressMap.get(dnsMessageId(msg.id(), question.name()));
         if (query != null) {
@@ -266,9 +266,12 @@ private <T> Future<T> lookupSingle(String name, DnsRecordType... types) {
   @SuppressWarnings("unchecked")
   private <T> Future<List<T>> lookupList(String name, DnsRecordType... types) {
     ContextInternal ctx = vertx.getOrCreateContext();
+    if (closed != null) {
+      return ctx.failedFuture(ConnectionBase.CLOSED_EXCEPTION);
+    }
     PromiseInternal<List<T>> promise = ctx.promise();
     Objects.requireNonNull(name, "no null name accepted");
-    EventLoop el = actualCtx.nettyEventLoop();
+    EventLoop el = context.nettyEventLoop();
     Query query = new Query(name, types);
     query.promise.addListener(promise);
     if (el.inEventLoop()) {
@@ -285,7 +288,7 @@ private long dnsMessageId(int id, String query) {
 
   // Testing purposes
   public void inProgressQueries(Handler<Integer> handler) {
-    actualCtx.runOnContext(v -> {
+    context.runOnContext(v -> {
       handler.handle(inProgressMap.size());
     });
   }
@@ -306,7 +309,7 @@ public Query(String name, DnsRecordType[] types) {
       for (DnsRecordType type: types) {
         msg.addRecord(DnsSection.QUESTION, new DefaultDnsQuestion(name, type, DnsRecord.CLASS_IN));
       }
-      this.promise = actualCtx.nettyEventLoop().newPromise();
+      this.promise = context.nettyEventLoop().newPromise();
       this.types = types;
       this.name = name;
     }
@@ -348,13 +351,13 @@ void run() {
       inProgressMap.put(dnsMessageId(msg.id(), name), this);
       timerID = vertx.setTimer(options.getQueryTimeout(), id -> {
         timerID = -1;
-        actualCtx.runOnContext(v -> {
+        context.runOnContext(v -> {
           fail(new VertxException("DNS query timeout for " + name));
         });
       });
       channel.writeAndFlush(msg).addListener((ChannelFutureListener) future -> {
         if (!future.isSuccess()) {
-          actualCtx.emit(future.cause(), this::fail);
+          context.emit(future.cause(), this::fail);
         }
       });
     }
@@ -368,4 +371,28 @@ private boolean isRequestedType(DnsRecordType dnsRecordType, DnsRecordType[] typ
       return false;
     }
   }
+
+  @Override
+  public void close(Handler<AsyncResult<Void>> handler) {
+    close().onComplete(handler);
+  }
+
+  @Override
+  public Future<Void> close() {
+    PromiseInternal<Void> promise;
+    synchronized (this) {
+      if (closed != null) {
+        return closed;
+      }
+      promise = vertx.promise();
+      closed = promise.future();
+    }
+    context.runOnContext(v -> {
+      new ArrayList<>(inProgressMap.values()).forEach(query -> {
+        query.fail(ConnectionBase.CLOSED_EXCEPTION);
+      });
+      channel.close().addListener(promise);
+    });
+    return promise.future();
+  }
 }

src/test/java/io/vertx/core/dns/DNSTest.java

@@ -11,33 +11,28 @@
 
 package io.vertx.core.dns;
 
-import static io.vertx.test.core.TestUtils.assertIllegalStateException;
 import static io.vertx.test.core.TestUtils.assertNullPointerException;
 
 import java.net.InetSocketAddress;
-import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
 
 import io.vertx.test.core.TestUtils;
 import io.vertx.test.core.VertxTestBase;
 import org.apache.directory.server.dns.messages.DnsMessage;
+import org.apache.directory.server.dns.store.RecordStore;
 import org.junit.Test;
 
-import io.vertx.core.AbstractVerticle;
-import io.vertx.core.DeploymentOptions;
 import io.vertx.core.Vertx;
 import io.vertx.core.VertxException;
 import io.vertx.core.VertxOptions;
-import io.vertx.core.dns.DnsClient;
-import io.vertx.core.dns.DnsClientOptions;
-import io.vertx.core.dns.DnsException;
-import io.vertx.core.dns.DnsResponseCode;
-import io.vertx.core.dns.MxRecord;
-import io.vertx.core.dns.SrvRecord;
 import io.vertx.core.dns.impl.DnsClientImpl;
 import io.vertx.test.fakedns.FakeDNSServer;
 import io.vertx.test.netty.TestLoggerFactory;
 
+import java.util.List;
+
 /**
  * @author <a href="mailto:nmaurer@redhat.com">Norman Maurer</a>
  * @author <a href="http://tfox.org">Tim Fox</a>
@@ -445,6 +440,37 @@ public void testRecursionNotDesired() throws Exception {
     await();
   }
 
+  @Test
+  public void testClose() throws Exception {
+    waitFor(2);
+    String ip = "10.0.0.1";
+    RecordStore store = dnsServer.testResolveA(ip).store();
+    CountDownLatch latch1 = new CountDownLatch(1);
+    CountDownLatch latch2 = new CountDownLatch(1);
+    dnsServer.store(question -> {
+      latch1.countDown();
+      try {
+        latch2.await(10, TimeUnit.SECONDS);
+      } catch (Exception e) {
+        fail(e);
+      }
+      return store.getRecords(question);
+    });
+    DnsClient dns = prepareDns();
+    dns
+      .resolveA("vertx.io")
+      .onComplete(onFailure(timeout -> {
+        assertTrue(timeout.getMessage().contains("closed"));
+        complete();
+      }));
+    awaitLatch(latch1);
+    dns.close().onComplete(onSuccess(v -> {
+      complete();
+      latch2.countDown();
+    }));
+    await();
+  }
+
   private DnsClient prepareDns() throws Exception {
     return prepareDns(new DnsClientOptions().setQueryTimeout(15000));
   }

src/test/java/io/vertx/test/fakedns/FakeDNSServer.java

@@ -93,6 +93,10 @@ public static RecordStore A_store(Function<String, String> entries) {
   public FakeDNSServer() {
   }
 
+  public RecordStore store() {
+    return store;
+  }
+
   public FakeDNSServer store(RecordStore store) {
     this.store = store;
     return this;