NIFI-4709 - Fixed ListAzureBlobStorage timestamp precision handling.

Signed-off-by: Pierre Villard <pierre.villard.fr@gmail.com>

This closes #2354.

nifi-nar-bundles/nifi-azure-bundle/nifi-azure-processors/src/main/java/org/apache/nifi/processors/azure/storage/ListAzureBlobStorage.java

@@ -134,6 +134,14 @@ public class ListAzureBlobStorage extends AbstractListProcessor<BlobInfo> {
         return Scope.CLUSTER;
     }
 
+    @Override
+    protected String getDefaultTimePrecision() {
+        // User does not have to choose one.
+        // AUTO_DETECT can handle most cases, but it may incur longer latency
+        // when all listed files do not have SECOND part in their timestamps although Azure Blob Storage does support seconds.
+        return PRECISION_SECONDS.getValue();
+    }
+
     @Override
     protected List<BlobInfo> performListing(final ProcessContext context, final Long minTimestamp) throws IOException {
         String containerName = context.getProperty(AzureStorageUtils.CONTAINER).evaluateAttributeExpressions().getValue();

nifi-nar-bundles/nifi-extension-utils/nifi-processor-utils/src/main/java/org/apache/nifi/processor/util/list/AbstractListProcessor.java

@@ -41,6 +41,7 @@ import org.apache.nifi.processor.ProcessContext;
 import org.apache.nifi.processor.ProcessSession;
 import org.apache.nifi.processor.Relationship;
 import org.apache.nifi.processor.exception.ProcessException;
+import org.apache.nifi.util.StringUtils;
 
 import java.io.File;
 import java.io.FileInputStream;
@@ -124,6 +125,10 @@ import java.util.stream.Collectors;
  * changing a property value. The {@link #isListingResetNecessary(PropertyDescriptor)} method is responsible for determining when the listing needs to be reset by returning
  * a boolean indicating whether or not a change in the value of the provided property should trigger the timestamp and identifier information to be cleared.
  * </li>
+ * <li>
+ * Provide the target system timestamp precision. By either letting user to choose the right one by adding TARGET_SYSTEM_TIMESTAMP_PRECISION to the return value of
+ * getSupportedPropertyDescriptors method or, overriding getDefaultTimePrecision method in case the target system has a fixed time precision.
+ * </li>
  * </ul>
  */
 @TriggerSerially
@@ -438,7 +443,11 @@ public abstract class AbstractListProcessor<T extends ListableEntity> extends Ab
             latestListedEntryTimestampThisCycleMillis = orderedEntries.lastKey();
 
             // Determine target system time precision.
-            final String specifiedPrecision = context.getProperty(TARGET_SYSTEM_TIMESTAMP_PRECISION).getValue();
+            String specifiedPrecision = context.getProperty(TARGET_SYSTEM_TIMESTAMP_PRECISION).getValue();
+            if (StringUtils.isBlank(specifiedPrecision)) {
+                // If TARGET_SYSTEM_TIMESTAMP_PRECISION is not supported by the Processor, then specifiedPrecision can be null, instead of its default value.
+                specifiedPrecision = getDefaultTimePrecision();
+            }
             final TimeUnit targetSystemTimePrecision
                     = PRECISION_AUTO_DETECT.getValue().equals(specifiedPrecision)
                         ? targetSystemHasMilliseconds ? TimeUnit.MILLISECONDS : targetSystemHasSeconds ? TimeUnit.SECONDS : TimeUnit.MINUTES
@@ -544,6 +553,17 @@ public abstract class AbstractListProcessor<T extends ListableEntity> extends Ab
         }
     }
 
+    /**
+     * This method is intended to be overridden by SubClasses those do not support TARGET_SYSTEM_TIMESTAMP_PRECISION property.
+     * So that it use return different precisions than PRECISION_AUTO_DETECT.
+     * If TARGET_SYSTEM_TIMESTAMP_PRECISION is supported as a valid Processor property,
+     * then PRECISION_AUTO_DETECT will be the default value when not specified by a user.
+     * @return
+     */
+    protected String getDefaultTimePrecision() {
+        return TARGET_SYSTEM_TIMESTAMP_PRECISION.getDefaultValue();
+    }
+
     private void resetTimeStates() {
         lastListedLatestEntryTimestampMillis = null;
         lastProcessedLatestEntryTimestampMillis = 0L;