[GitHub] [cassandra] yifan-c commented on a change in pull request #1438: CASSANDRA-17347 Fix NullPointerException during StartupClusterConnectivityChecker

[GitBox <gi...@apache.org>]

yifan-c commented on a change in pull request #1438:
URL: https://github.com/apache/cassandra/pull/1438#discussion_r799729740



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File path: src/java/org/apache/cassandra/net/StartupClusterConnectivityChecker.java
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@@ -171,7 +172,10 @@ public boolean execute(Set<InetAddressAndPort> peers, Function<InetAddressAndPor
         {
             // dc -> missing peer host addresses
             Map<String, List<String>> peersDown = acks.getMissingPeers().stream()
-                                                      .collect(groupingBy(peerToDatacenter::get,
+                                                      .collect(groupingBy(peer -> {
+                                                                              String dc = peerToDatacenter.get(peer);
+                                                                              return dc != null ? dc : StringUtils.defaultString(getDatacenterSource.apply(peer), "unknown");

Review comment:
       The goal is here very simple, i.e. try to resolve the value from the map cache, if not try to resolve from snitch, if all attempts fail, use the default "unknown". 
   There are so many ways to express it in the code and all correctly. Functional, ternary operator, or just the plain `if`
   In this particular scenario, I would rate the plain `if` to have the best readability, then the ternary operator. Functional seems a bit overkill. 




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