TotalOrderMulticastSender

1 files changed, 53 insertions, 0 deletions

diff --git a/src/main/java/derms/net/tomulticast/TotalOrderMulticast.java b/src/main/java/derms/net/tomulticast/TotalOrderMulticast.java
new file mode 100644
index 0000000..d83a34d
--- /dev/null
+++ b/src/main/java/derms/net/tomulticast/TotalOrderMulticast.java
@@ -0,0 +1,53 @@
+package derms.net.tomulticast;
+
+import derms.net.rmulticast.MessagePayload;
+import derms.net.rmulticast.ReliableMulticast;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.util.logging.Logger;
+
+/**
+ * <p>A single-sender, multiple-receiver multicast group that enforces a total order on
+ * received messages. If a process delivers message <i>A</i> before message <i>B</i>,
+ * then all other processes will deliver <i>A</i> and <i>B</i> in the same order
+ * (<i>A</i> before <i>B</i>).</p>
+ *
+ * <p>Additionally, the protocol guarantees reliable delivery of messages. If the sender
+ * crashes while sending a message, either all processes will receive the message, or
+ * none of them will.</p>
+ *
+ * <p><b>Only one sender is allowed per multicast group</b>, but a group may have multiple
+ * receivers. Use {@link derms.net.tomulticast.TotalOrderMulticastSender} to send
+ * messages, and {@link derms.net.tomulticast.TotalOrderMulticastReceiver} to receive
+ * them.</p>
+ */
+public abstract class TotalOrderMulticast<T extends MessagePayload> {
+    final ReliableMulticast<Message<T>> sock;
+    protected final InetSocketAddress group;
+    protected Long seq; // Sequence number.
+    protected final Logger log;
+
+    protected TotalOrderMulticast(InetSocketAddress group, InetAddress laddr) throws IOException {
+        this.sock = new ReliableMulticast<Message<T>>(group, laddr);
+        this.group = group;
+        this.seq = (long) 0;
+        this.log = Logger.getLogger(this.getClass().getName());
+    }
+
+    /** Close the underlying socket. */
+    public void close() {
+        sock.close();
+    }
+
+    /** Increment the sequence number. */
+    protected void incSeq() {
+        if (seq < seq.MAX_VALUE) {
+            seq++;
+        } else {
+            log.warning("Sequence number overflow. Wrapping to 0.");
+            seq = (long) 0;
+        }
+    }
+}