Decode devp2p packets off the event thread

ethereum/p2p/src/main/java/tech/pegasys/pantheon/ethereum/p2p/discovery/VertxPeerDiscoveryAgent.java

@@ -26,7 +26,6 @@
 import tech.pegasys.pantheon.metrics.MetricCategory;
 import tech.pegasys.pantheon.metrics.MetricsSystem;
 import tech.pegasys.pantheon.util.NetworkUtility;
-import tech.pegasys.pantheon.util.Preconditions;
 
 import java.io.IOException;
 import java.net.BindException;
@@ -197,26 +196,34 @@ private void handleException(final Throwable exception) {
    * @param datagram the received datagram.
    */
   private void handlePacket(final DatagramPacket datagram) {
-    try {
-      final int length = datagram.data().length();
-      Preconditions.checkGuard(
-          validatePacketSize(length),
-          PeerDiscoveryPacketDecodingException::new,
-          "Packet too large. Actual size (bytes): %s",
-          length);
-
-      // We allow exceptions to bubble up, as they'll be picked up by the exception handler.
-      final Packet packet = Packet.decode(datagram.data());
-      // Acquire the senders coordinates to build a Peer representation from them.
-      final String host = datagram.sender().host();
-      final int port = datagram.sender().port();
-      final Endpoint endpoint = new Endpoint(host, port, OptionalInt.empty());
-      handleIncomingPacket(endpoint, packet);
-    } catch (final PeerDiscoveryPacketDecodingException e) {
-      LOG.debug("Discarding invalid peer discovery packet: {}", e.getMessage());
-    } catch (final Throwable t) {
-      LOG.error("Encountered error while handling packet", t);
+    final int length = datagram.data().length();
+    if (!validatePacketSize(length)) {
+      LOG.debug("Discarding over-sized packet. Actual size (bytes): " + length);
+      return;
     }
+    vertx.<Packet>executeBlocking(
+        future -> {
+          try {
+            future.complete(Packet.decode(datagram.data()));
+          } catch (final Throwable t) {
+            future.fail(t);
+          }
+        },
+        event -> {
+          if (event.succeeded()) {
+            // Acquire the senders coordinates to build a Peer representation from them.
+            final String host = datagram.sender().host();
+            final int port = datagram.sender().port();
+            final Endpoint endpoint = new Endpoint(host, port, OptionalInt.empty());
+            handleIncomingPacket(endpoint, event.result());
+          } else {
+            if (event.cause() instanceof PeerDiscoveryPacketDecodingException) {
+              LOG.debug("Discarding invalid peer discovery packet: {}", event.cause().getMessage());
+            } else {
+              LOG.error("Encountered error while handling packet", event.cause());
+            }
+          }
+        });
   }
 
   private class VertxAsyncExecutor implements AsyncExecutor {