GOSSIP-62 Implement Crdt PN-Counter

restored layout of pom.xml for minimal changes in PR

Snapshot - I think I have the basic framework in place. No tests are passing and nothing works, but most of the calls and the builder are in place.

capture working code

starting working on example code

Working examples

GOSSIP-65 Implement crdt LWW-Element-Set

LWWSet implemented + se/de + unit tests + jackson tests + DataTests

GOSSIP-55 Added event handlers to notify share data and per node data changes

Reformat code to match apache standard

Fixed DataTest errors WRT PNCounter

gossip-examples/src/main/java/org/apache/gossip/examples/StandAlonePNCounter.java

@@ -0,0 +1,170 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.gossip.examples;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.net.URI;
+import java.util.Arrays;
+import java.util.List;
+
+import org.apache.gossip.GossipSettings;
+import org.apache.gossip.LocalMember;
+import org.apache.gossip.RemoteMember;
+import org.apache.gossip.crdt.PNCounter;
+import org.apache.gossip.manager.GossipManager;
+import org.apache.gossip.manager.GossipManagerBuilder;
+import org.apache.gossip.model.SharedDataMessage;
+
+public class StandAlonePNCounter {
+  private static ExampleCommon common = new ExampleCommon();
+  private static String lastInput = "{None}";
+
+  public static void main(String[] args) throws InterruptedException, IOException {
+    args = common.checkArgsForClearFlag(args);
+    GossipSettings s = new GossipSettings();
+    s.setWindowSize(1000);
+    s.setGossipInterval(100);
+    GossipManager gossipService = GossipManagerBuilder
+            .newBuilder()
+            .cluster("mycluster")
+            .uri(URI.create(args[0])).id(args[1])
+            .gossipMembers(
+                    Arrays.asList(new RemoteMember("mycluster", URI.create(args[2]), args[3])))
+            .gossipSettings(s)
+            .build();
+    gossipService.init();
+
+    new Thread(() -> {
+      while (true) {
+        common.optionallyClearTerminal();
+        printLiveMembers(gossipService);
+        printDeadMambers(gossipService);
+        printValues(gossipService);
+        try {
+          Thread.sleep(2000);
+        } catch (Exception ignore) {
+        }
+      }
+    }).start();
+
+    String line = null;
+    try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
+      while ((line = br.readLine()) != null) {
+        System.out.println(line);
+        char op = line.charAt(0);
+        char blank = line.charAt(1);
+        String val = line.substring(2);
+        Long l = null;
+        boolean valid = true;
+        try {
+           l = Long.valueOf(val);
+        } catch (NumberFormatException ex) {
+          valid = false;
+        }
+        valid = valid &&
+          (
+            (blank == ' ') &&
+            ((op == 'i') || (op == 'd'))
+          );
+        if (valid) {
+          if (op == 'i') {
+            increment(l, gossipService);
+          } else if (op == 'd') {
+            decrement(l, gossipService);
+          }
+        }
+        setLastInput(line,valid);
+      }
+    }
+  }
+
+  private static void printValues(GossipManager gossipService) {
+    System.out.println("Last Input: " + getLastInput());
+    System.out.println("---------- " + (gossipService.findCrdt("myPNCounter") == null ? ""
+            : gossipService.findCrdt("myPNCounter").value()));
+    System.out.println("********** " + gossipService.findCrdt("myPNCounter"));
+  }
+
+  private static void printDeadMambers(GossipManager gossipService) {
+    List<LocalMember> members = gossipService.getDeadMembers();
+    if (members.isEmpty()) {
+       System.out.println("Dead: (none)");
+       return;
+    }
+    System.out.println("Dead: " + members.get(0));
+    for (int i = 1; i < members.size(); i++) {
+      System.out.println("    : " + members.get(i)); 
+    }
+  }
+
+  private static void printLiveMembers(GossipManager gossipService) {
+    List<LocalMember> members = gossipService.getLiveMembers();
+    if (members.isEmpty()) {
+       System.out.println("Live: (none)");
+       return;
+    }
+    System.out.println("Live: " + members.get(0));
+    for (int i = 1; i < members.size(); i++) {
+      System.out.println("    : " + members.get(i)); 
+    }
+  }
+
+  private static void increment(Long l, GossipManager gossipManager) {
+    PNCounter c = (PNCounter) gossipManager.findCrdt("myPNCounter");
+    if (c == null) {
+      c = new PNCounter(new PNCounter.Builder(gossipManager).increment((l)));
+    } else {
+      c = new PNCounter(c, new PNCounter.Builder(gossipManager).increment((l)));
+    }
+    SharedDataMessage m = new SharedDataMessage();
+    m.setExpireAt(Long.MAX_VALUE);
+    m.setKey("myPNCounter");
+    m.setPayload(c);
+    m.setTimestamp(System.currentTimeMillis());
+    gossipManager.merge(m);
+  }
+
+  private static void decrement(Long l, GossipManager gossipManager) {
+    PNCounter c = (PNCounter) gossipManager.findCrdt("myPNCounter");
+    if (c == null) {
+      c = new PNCounter(new PNCounter.Builder(gossipManager).decrement((l)));
+    } else {
+      c = new PNCounter(c, new PNCounter.Builder(gossipManager).decrement((l)));
+    }
+    SharedDataMessage m = new SharedDataMessage();
+    m.setExpireAt(Long.MAX_VALUE);
+    m.setKey("myPNCounter");
+    m.setPayload(c);
+    m.setTimestamp(System.currentTimeMillis());
+    gossipManager.merge(m);
+  }
+  
+  private static void setLastInput(String input, boolean valid) {
+    lastInput = input;
+    if (! valid) {
+      lastInput += " (invalid)";
+    }
+  }
+
+  private static String getLastInput() {
+    return lastInput;
+  }
+
+}