Prefer approx timestamp if flag set.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "aws-lambda-stream",
-  "version": "1.1.0",
+  "version": "1.1.1",
   "description": "Create stream processors with AWS Lambda functions.",
   "keywords": [
     "aws",

src/from/dynamodb.js

@@ -11,6 +11,7 @@ export const fromDynamodb = (event, {
   eventTypePrefix = undefined,
   ignoreTtlExpiredEvents = false,
   ignoreReplicas = true,
+  preferApproximateTimestamp = false,
 } = {}) => // eslint-disable-line import/prefer-default-export
 
   // prepare the event stream
@@ -34,7 +35,7 @@ export const fromDynamodb = (event, {
           id: record.eventID,
           type: `${calculateEventTypePrefix(record, { skFn, discriminatorFn, eventTypePrefix })}-${calculateEventTypeSuffix(record)}`,
           partitionKey: record.dynamodb.Keys[pkFn].S,
-          timestamp: deriveTimestamp(record),
+          timestamp: deriveTimestamp(record, preferApproximateTimestamp),
           tags: {
             region: record.awsRegion,
           },
@@ -88,8 +89,13 @@ const calculateEventTypeSuffix = (record) => {
   return suffix;
 };
 
-const deriveTimestamp = (record) =>
-  parseInt(record.dynamodb.NewImage?.timestamp?.N, 10) || ddbApproximateCreationTimestamp(record);
+const deriveTimestamp = (record, preferApproximateTimestamp) => {
+  if (preferApproximateTimestamp) {
+    return ddbApproximateCreationTimestamp(record);
+  } else {
+    return parseInt(record.dynamodb.NewImage?.timestamp?.N, 10) || ddbApproximateCreationTimestamp(record);
+  }
+};
 
 export const ddbApproximateCreationTimestamp = (record) => record.dynamodb.ApproximateCreationDateTime * 1000;
 

test/unit/from/dynamodb.test.js

@@ -221,6 +221,116 @@ describe('from/dynamodb.js', () => {
       .done(done);
   });
 
+  it('should prefer approximate timestamp if flag set', (done) => {
+    const events = toDynamodbRecords([
+      {
+        timestamp: 1572832690,
+        keys: {
+          pk: '1',
+          sk: 'thing',
+        },
+        newImage: {
+          pk: '1',
+          sk: 'thing',
+          discriminator: 'thing',
+          name: 'n1',
+          timestamp: 1572832690001,
+          // insert in the current region will not have the awsregion field
+        },
+      },
+      // dynamodb stream emits an extra update event as it adorns the 'aws:rep' global table metadata
+      // so this extra event should be skipped
+      {
+        timestamp: 1572832690,
+        keys: {
+          pk: '1',
+          sk: 'thing',
+        },
+        newImage: {
+          pk: '1',
+          sk: 'thing',
+          discriminator: 'thing',
+          name: 'n1',
+          awsregion: 'us-west-2',
+        },
+        oldImage: {
+          pk: '1',
+          sk: 'thing',
+          discriminator: 'thing',
+          name: 'n1',
+          // as mentioned above there was no awsregion field on the insert event
+        },
+      },
+    ]);
+
+    fromDynamodb(events, { preferApproximateTimestamp: true })
+      .collect()
+      .tap((collected) => {
+        // console.log(JSON.stringify(collected, null, 2));
+
+        expect(collected.length).to.equal(1);
+        expect(collected[0]).to.deep.equal({
+          record: {
+            eventID: '0',
+            eventName: 'INSERT',
+            eventSource: 'aws:dynamodb',
+            awsRegion: 'us-west-2',
+            dynamodb: {
+              ApproximateCreationDateTime: 1572832690,
+              Keys: {
+                pk: {
+                  S: '1',
+                },
+                sk: {
+                  S: 'thing',
+                },
+              },
+              NewImage: {
+                pk: {
+                  S: '1',
+                },
+                sk: {
+                  S: 'thing',
+                },
+                discriminator: {
+                  S: 'thing',
+                },
+                name: {
+                  S: 'n1',
+                },
+                timestamp: {
+                  N: '1572832690001',
+                },
+              },
+              OldImage: undefined,
+              SequenceNumber: '0',
+              StreamViewType: 'NEW_AND_OLD_IMAGES',
+            },
+          },
+          event: {
+            id: '0',
+            type: 'thing-created',
+            partitionKey: '1',
+            timestamp: 1572832690000,
+            tags: {
+              region: 'us-west-2',
+            },
+            raw: {
+              new: {
+                pk: '1',
+                sk: 'thing',
+                discriminator: 'thing',
+                name: 'n1',
+                timestamp: 1572832690001,
+              },
+              old: undefined,
+            },
+          },
+        });
+      })
+      .done(done);
+  });
+
   it('should parse MODIFY record', (done) => {
     const events = toDynamodbRecords([
       {