Add a system property to set hostId if not yet initialized

patch by Abi Palagashvili; reviewed by Stefan Miklosovic and Paulo Motta for CASSANDRA-14582

CHANGES.txt

@@ -1,4 +1,5 @@
 4.1
+ * Add a system property to set hostId if not yet initialized (CASSANDRA-14582)
  * GossiperTest.testHasVersion3Nodes didn't take into account trunk version changes, fixed to rely on latest version (CASSANDRA-16651)
 Merged from 4.0:
  * Make JmxHistogram#getRecentValues() and JmxTimer#getRecentValues() thread-safe (CASSANDRA-16707)

conf/jvm-server.options

@@ -22,6 +22,9 @@
 # and perhaps have affinity.
 #-Dcassandra.available_processors=number_of_processors
 
+# Specify host id for the first boot and persist it
+#-Dcassandra.host_id_first_boot=host_id
+
 # The directory location of the cassandra.yaml file.
 #-Dcassandra.config=directory
 

src/java/org/apache/cassandra/db/SystemKeyspace.java

@@ -1126,13 +1126,15 @@ public final class SystemKeyspace
             return hostId;
 
         // ID not found, generate a new one, persist, and then return it.
-        hostId = UUID.randomUUID();
+        String hostString = System.getProperty("cassandra.host_id_first_boot", UUID.randomUUID().toString());
+        hostId = UUID.fromString(hostString);
         logger.warn("No host ID found, created {} (Note: This should happen exactly once per node).", hostId);
         return setLocalHostId(hostId);
     }
 
     /**
-     * Sets the local host ID explicitly.  Should only be called outside of SystemTable when replacing a node.
+     * Sets the local host ID explicitly. Should only be called outside of SystemTable when replacing a node.
+     * Used also in CASSANDRA-14582.
      */
     public static synchronized UUID setLocalHostId(UUID hostId)
     {