Refactor validation logic in StorageService.rebuild

patch by Stefan Miklosovic; reviewed by Ariel Weisberg for CASSANDRA-18803

Author: smiklosovic

CHANGES.txt

@@ -1,4 +1,5 @@
 3.0.30
+ * Refactor validation logic in StorageService.rebuild (CASSANDRA-18803)
  * Make alternation of a user type validate the same way as creation of a user type does (CASSANDRA-18585)
  * Backport of CASSANDRA-16905 Further restrict schema column drop/recreate conversions (CASSANDRA-18760)
  * CQLSH emits a warning when the server version doesn't match (CASSANDRA-18745)

src/java/org/apache/cassandra/service/StorageService.java

@@ -1308,35 +1308,27 @@ public boolean isJoined()
 
     public void rebuild(String sourceDc)
     {
-        try
+        if (sourceDc != null)
         {
-            // check ongoing rebuild
-            if (!isRebuilding.compareAndSet(false, true))
+            TokenMetadata.Topology topology = getTokenMetadata().cloneOnlyTokenMap().getTopology();
+            Set<String> availableDCs = topology.getDatacenterEndpoints().keySet();
+            if (!availableDCs.contains(sourceDc))
             {
-                throw new IllegalStateException("Node is still rebuilding. Check nodetool netstats.");
-            }
-
-            if (sourceDc != null)
-            {
-                TokenMetadata.Topology topology = getTokenMetadata().cloneOnlyTokenMap().getTopology();
-                Set<String> availableDCs = topology.getDatacenterEndpoints().keySet();
-                if (!availableDCs.contains(sourceDc))
-                {
-                    throw new IllegalArgumentException(String.format("Provided datacenter '%s' is not a valid datacenter, available datacenters are: %s",
-                                                                     sourceDc, String.join(",", availableDCs)));
-                }
+                throw new IllegalArgumentException(String.format("Provided datacenter '%s' is not a valid datacenter, available datacenters are: %s",
+                                                                 sourceDc, String.join(",", availableDCs)));
             }
         }
-        catch (Throwable ex)
+
+        // check ongoing rebuild
+        if (!isRebuilding.compareAndSet(false, true))
         {
-            isRebuilding.set(false);
-            throw ex;
+            throw new IllegalStateException("Node is still rebuilding. Check nodetool netstats.");
         }
 
-        logger.info("rebuild from dc: {}", sourceDc == null ? "(any dc)" : sourceDc);
-
         try
         {
+            logger.info("rebuild from dc: {}", sourceDc == null ? "(any dc)" : sourceDc);
+
             RangeStreamer streamer = new RangeStreamer(tokenMetadata,
                                                        null,
                                                        FBUtilities.getBroadcastAddress(),