An logging example

Add the example how internal logger can be used.

Follows on: #194

Author: nicktorwald

src/main/java/org/tarantool/cluster/TarantoolClusterStoredFunctionDiscoverer.java

@@ -3,12 +3,13 @@
 import org.tarantool.TarantoolClient;
 import org.tarantool.TarantoolClientOps;
 import org.tarantool.TarantoolClusterClientConfig;
+import org.tarantool.logging.Logger;
+import org.tarantool.logging.LoggerFactory;
 import org.tarantool.util.StringUtils;
 
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
-import java.util.stream.Collectors;
 
 /**
  * A cluster nodes discoverer based on calling a predefined function
@@ -19,6 +20,8 @@
  */
 public class TarantoolClusterStoredFunctionDiscoverer implements TarantoolClusterDiscoverer {
 
+    private static final Logger LOGGER = LoggerFactory.getLogger(TarantoolClusterStoredFunctionDiscoverer.class);
+
     private TarantoolClient client;
     private String entryFunction;
 
@@ -57,12 +60,23 @@ private Set<String> checkAndFilterAddresses(List<?> result) {
             throw new IllegalDiscoveryFunctionResult("The first value must be an array of strings");
         }
 
-        return ((List<Object>) result.get(0)).stream()
-            .filter(item -> item instanceof String)
-            .map(Object::toString)
-            .filter(s -> !StringUtils.isBlank(s))
-            .filter(this::isAddress)
-            .collect(Collectors.toCollection(LinkedHashSet::new));
+        LinkedHashSet<String> passed = new LinkedHashSet<>();
+        LinkedHashSet<String> skipped = new LinkedHashSet<>();
+        for (Object item : ((List<Object>) result.get(0))) {
+            if (!(item instanceof String)) {
+                continue;
+            }
+            String s = item.toString();
+            if (!StringUtils.isBlank(s) && isAddress(s)) {
+                passed.add(s);
+            } else {
+                skipped.add(s);
+            }
+        }
+        if (!skipped.isEmpty()) {
+            LOGGER.warn("Some of the addresses were skipped because of unsupported format: {0}", skipped);
+        }
+        return passed;
     }
 
     /**