minor, add more logs to troubleshot a mysterious NPE in ScannerWorker…

….java (#3361)
solversa · Nov 28, 2017 · 924c667 · 924c667
1 parent fbd83ce
commit 924c667
Showing 1 changed file with 18 additions and 4 deletions.
diff --git a/core-storage/src/main/java/org/apache/kylin/storage/gtrecord/ScannerWorker.java b/core-storage/src/main/java/org/apache/kylin/storage/gtrecord/ScannerWorker.java
@@ -19,7 +19,7 @@
 package org.apache.kylin.storage.gtrecord;
 
 import java.io.IOException;
-import java.lang.reflect.InvocationTargetException;
+import java.util.Arrays;
 import java.util.Iterator;
 
 import org.apache.kylin.cube.cuboid.Cuboid;
@@ -39,10 +39,15 @@
 public class ScannerWorker {
 
     private static final Logger logger = LoggerFactory.getLogger(ScannerWorker.class);
-    private IGTScanner internal = null;
+
+    private final IGTScanner internal;
+    private final Object[] inputArgs;
 
     public ScannerWorker(ISegment segment, Cuboid cuboid, GTScanRequest scanRequest, String gtStorage,
             StorageContext context) {
+
+        inputArgs = new Object[] { segment, cuboid, scanRequest, gtStorage, context };
+
         try (TraceScope scope = Trace.startSpan("visit segment " + segment.getName())) {
 
             if (scanRequest == null) {
@@ -58,21 +63,30 @@ public ScannerWorker(ISegment segment, Cuboid cuboid, GTScanRequest scanRequest,
                         .getConstructor(ISegment.class, Cuboid.class, GTInfo.class, StorageContext.class)
                         .newInstance(segment, cuboid, info, context); // default behavior
                 internal = rpc.getGTScanner(scanRequest);
-            } catch (IOException | InstantiationException | InvocationTargetException | IllegalAccessException
-                    | ClassNotFoundException | NoSuchMethodException e) {
+            } catch (Exception e) {
                 throw new RuntimeException(e);
             }
         }
+
+        checkNPE();
     }
 
     public boolean isSegmentSkipped() {
         return internal instanceof EmptyGTScanner;
     }
 
     public Iterator<GTRecord> iterator() {
+        // to troubleshoot a myth NPE on line: return internal.iterator()
+        checkNPE();
         return internal.iterator();
     }
 
+    private void checkNPE() {
+        if (internal == null) {
+            logger.error("Caught an impossible NPE, args are " + Arrays.toString(inputArgs), new Exception());
+        }
+    }
+
     public void close() throws IOException {
         internal.close();
     }