GOSSIP-25 Create reaper process to expire per-node data

src/test/java/org/apache/gossip/manager/DataReaperTest.java

@@ -0,0 +1,55 @@
+package org.apache.gossip.manager;
+
+import java.net.URI;
+
+import org.apache.gossip.GossipSettings;
+import org.apache.gossip.manager.random.RandomGossipManager;
+import org.apache.gossip.model.GossipDataMessage;
+import org.junit.Assert;
+import org.junit.Test;
+
+import io.teknek.tunit.TUnit;
+
+public class DataReaperTest {
+
+  @Test
+  public void testReaperOneShot() {
+    String myId = "4";
+    String key = "key";
+    String value = "a";
+    GossipSettings settings = new GossipSettings();
+    GossipManager gm = RandomGossipManager.newBuilder().cluster("abc").settings(settings)
+            .withId(myId).uri(URI.create("udp://localhost:5000")).build();
+    gm.gossipPerNodeData(perNodeDatum(key, value));
+    Assert.assertEquals(value, gm.findGossipData(myId, key).getPayload());
+    gm.getDataReaper().runOnce();
+    TUnit.assertThat(() -> gm.findGossipData(myId, key)).equals(null);
+  }
+
+  private GossipDataMessage perNodeDatum(String key, String value) {
+    GossipDataMessage m = new GossipDataMessage();
+    m.setExpireAt(System.currentTimeMillis() + 5L);
+    m.setKey(key);
+    m.setPayload(value);
+    m.setTimestamp(System.currentTimeMillis());
+    return m;
+  }
+
+  @Test
+  public void testHigherTimestampWins() {
+    String myId = "4";
+    String key = "key";
+    String value = "a";
+    GossipSettings settings = new GossipSettings();
+    GossipManager gm = RandomGossipManager.newBuilder().cluster("abc").settings(settings)
+            .withId(myId).uri(URI.create("udp://localhost:5000")).build();
+    GossipDataMessage before = perNodeDatum(key, value);
+    GossipDataMessage after = perNodeDatum(key, "b");
+    after.setTimestamp(after.getTimestamp() - 1);
+    gm.gossipPerNodeData(before);
+    Assert.assertEquals(value, gm.findGossipData(myId, key).getPayload());
+    gm.gossipPerNodeData(after);
+    Assert.assertEquals(value, gm.findGossipData(myId, key).getPayload());
+  }
+
+}