reliable multicast: announce presence to group

1 files changed, 47 insertions, 0 deletions

diff --git a/src/main/java/derms/net/rmulticast/Announce.java b/src/main/java/derms/net/rmulticast/Announce.java
new file mode 100644
index 0000000..08d817d
--- /dev/null
+++ b/src/main/java/derms/net/rmulticast/Announce.java
@@ -0,0 +1,47 @@
+package derms.net.rmulticast;
+
+import derms.net.ConcurrentMulticastSocket;
+import derms.net.Packet;
+
+import java.io.IOException;
+import java.net.DatagramPacket;
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.time.Duration;
+import java.util.logging.Logger;
+
+/**
+ * Periodically announce the presence of the local process to the group.
+ * Allows processes to populate their set of group members, even if not
+ * all members would normally send messages to the group.
+ */
+class Announce implements Runnable {
+    private static final Duration period = Duration.ofSeconds(30);
+
+    private final DatagramPacket pkt;
+    private final ConcurrentMulticastSocket outSock;
+    private final Logger log;
+
+    Announce(InetSocketAddress group, InetAddress laddr, ConcurrentMulticastSocket outSock) throws IOException {
+        AnnounceMessage msg = new AnnounceMessage(laddr);
+        this.pkt = Packet.encode(msg, group);
+        this.outSock = outSock;
+        this.log = Logger.getLogger(this.getClass().getName());
+    }
+
+    @Override
+    public void run() {
+        try {
+            for (;;) {
+                try {
+                    Wait.forDuration(period);
+                    outSock.send(pkt);
+                } catch (IOException e) {
+                    log.warning(e.getMessage());
+                }
+            }
+        } catch (InterruptedException e) {
+            log.info("Announce thread interrupted: " + e.getMessage());
+        }
+    }
+}