API de bajo nivel de DynamoDB Streams: ejemplo en Java - Amazon DynamoDB

API de bajo nivel de DynamoDB Streams: ejemplo en Java

nota

El código que se presenta en esta página no es exhaustivo y no contempla todos los escenarios de consumo de Amazon DynamoDB Streams. La manera recomendada de consumir registros de transmisión de DynamoDB consiste en usar Amazon Kinesis Adapter con la Kinesis Client Library (KCL), como se describe en Uso del adaptador Kinesis de DynamoDB Streams para procesar registros de transmisión.

Esta sección contiene un programa de Java que muestra el funcionamiento de DynamoDB Streams. El programa realiza lo siguiente:

  1. Crea una tabla de DynamoDB con una transmisión habilitada.

  2. Describe los ajustes de secuencia de esta tabla.

  3. Modifica los datos de la tabla.

  4. Describe los fragmentos de la secuencia.

  5. Lee los registros de secuencia de los fragmentos.

  6. Elimina recursos.

Al ejecutar el programa, verá un resultado parecido al siguiente.

Issuing CreateTable request for TestTableForStreams
Waiting for TestTableForStreams to be created...
Current stream ARN for TestTableForStreams: arn:aws:dynamodb:us-east-2:123456789012:table/TestTableForStreams/stream/2018-03-20T16:49:55.208
Stream enabled: true
Update view type: NEW_AND_OLD_IMAGES

Performing write activities on TestTableForStreams
Processing item 1 of 100
Processing item 2 of 100
Processing item 3 of 100
...
Processing item 100 of 100

Shard: {ShardId: shardId-1234567890-...,SequenceNumberRange: {StartingSequenceNumber: 01234567890...,},}
    Shard iterator: EjYFEkX2a26eVTWe...
        ApproximateCreationDateTime: Tue Mar 20 09:50:00 PDT 2018,Keys: {Id={N: 1,}},NewImage: {Message={S: New item!,}, Id={N: 1,}},SequenceNumber: 100000000003218256368,SizeBytes: 24,StreamViewType: NEW_AND_OLD_IMAGES}
         {ApproximateCreationDateTime: Tue Mar 20 09:50:00 PDT 2018,Keys: {Id={N: 1,}},NewImage: {Message={S: This item has changed,}, Id={N: 1,}},OldImage: {Message={S: New item!,}, Id={N: 1,}},SequenceNumber: 200000000003218256412,SizeBytes: 56,StreamViewType: NEW_AND_OLD_IMAGES}
         {ApproximateCreationDateTime: Tue Mar 20 09:50:00 PDT 2018,Keys: {Id={N: 1,}},OldImage: {Message={S: This item has changed,}, Id={N: 1,}},SequenceNumber: 300000000003218256413,SizeBytes: 36,StreamViewType: NEW_AND_OLD_IMAGES}
...
Deleting the table...
Demo complete

ejemplo 

package com.amazon.codesamples;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import com.amazonaws.AmazonClientException;
import com.amazonaws.auth.DefaultAWSCredentialsProviderChain;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBStreams;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBStreamsClientBuilder;
import com.amazonaws.services.dynamodbv2.model.AttributeAction;
import com.amazonaws.services.dynamodbv2.model.AttributeDefinition;
import com.amazonaws.services.dynamodbv2.model.AttributeValue;
import com.amazonaws.services.dynamodbv2.model.AttributeValueUpdate;
import com.amazonaws.services.dynamodbv2.model.CreateTableRequest;
import com.amazonaws.services.dynamodbv2.model.DescribeStreamRequest;
import com.amazonaws.services.dynamodbv2.model.DescribeStreamResult;
import com.amazonaws.services.dynamodbv2.model.DescribeTableResult;
import com.amazonaws.services.dynamodbv2.model.GetRecordsRequest;
import com.amazonaws.services.dynamodbv2.model.GetRecordsResult;
import com.amazonaws.services.dynamodbv2.model.GetShardIteratorRequest;
import com.amazonaws.services.dynamodbv2.model.GetShardIteratorResult;
import com.amazonaws.services.dynamodbv2.model.KeySchemaElement;
import com.amazonaws.services.dynamodbv2.model.KeyType;
import com.amazonaws.services.dynamodbv2.model.ProvisionedThroughput;
import com.amazonaws.services.dynamodbv2.model.Record;
import com.amazonaws.services.dynamodbv2.model.Shard;
import com.amazonaws.services.dynamodbv2.model.ShardIteratorType;
import com.amazonaws.services.dynamodbv2.model.StreamSpecification;
import com.amazonaws.services.dynamodbv2.model.StreamViewType;
import com.amazonaws.services.dynamodbv2.util.TableUtils;

public class StreamsLowLevelDemo {

        public static void main(String args[]) throws InterruptedException {

                AmazonDynamoDB dynamoDBClient = AmazonDynamoDBClientBuilder
                                .standard()
                                .withRegion(Regions.US_EAST_2)
                                .withCredentials(new DefaultAWSCredentialsProviderChain())
                                .build();

                AmazonDynamoDBStreams streamsClient = AmazonDynamoDBStreamsClientBuilder
                                .standard()
                                .withRegion(Regions.US_EAST_2)
                                .withCredentials(new DefaultAWSCredentialsProviderChain())
                                .build();

                // Create a table, with a stream enabled
                String tableName = "TestTableForStreams";

                ArrayList<AttributeDefinition> attributeDefinitions = new ArrayList<>(
                                Arrays.asList(new AttributeDefinition()
                                                .withAttributeName("Id")
                                                .withAttributeType("N")));

                ArrayList<KeySchemaElement> keySchema = new ArrayList<>(
                                Arrays.asList(new KeySchemaElement()
                                                .withAttributeName("Id")
                                                .withKeyType(KeyType.HASH))); // Partition key

                StreamSpecification streamSpecification = new StreamSpecification()
                                .withStreamEnabled(true)
                                .withStreamViewType(StreamViewType.NEW_AND_OLD_IMAGES);

                CreateTableRequest createTableRequest = new CreateTableRequest().withTableName(tableName)
                                .withKeySchema(keySchema).withAttributeDefinitions(attributeDefinitions)
                                .withProvisionedThroughput(new ProvisionedThroughput()
                                                .withReadCapacityUnits(10L)
                                                .withWriteCapacityUnits(10L))
                                .withStreamSpecification(streamSpecification);

                System.out.println("Issuing CreateTable request for " + tableName);
                dynamoDBClient.createTable(createTableRequest);
                System.out.println("Waiting for " + tableName + " to be created...");

                try {
                        TableUtils.waitUntilActive(dynamoDBClient, tableName);
                } catch (AmazonClientException e) {
                        e.printStackTrace();
                }

                // Print the stream settings for the table
                DescribeTableResult describeTableResult = dynamoDBClient.describeTable(tableName);
                String streamArn = describeTableResult.getTable().getLatestStreamArn();
                System.out.println("Current stream ARN for " + tableName + ": " +
                                describeTableResult.getTable().getLatestStreamArn());
                StreamSpecification streamSpec = describeTableResult.getTable().getStreamSpecification();
                System.out.println("Stream enabled: " + streamSpec.getStreamEnabled());
                System.out.println("Update view type: " + streamSpec.getStreamViewType());
                System.out.println();

                // Generate write activity in the table

                System.out.println("Performing write activities on " + tableName);
                int maxItemCount = 100;
                for (Integer i = 1; i <= maxItemCount; i++) {
                        System.out.println("Processing item " + i + " of " + maxItemCount);

                        // Write a new item
                        Map<String, AttributeValue> item = new HashMap<>();
                        item.put("Id", new AttributeValue().withN(i.toString()));
                        item.put("Message", new AttributeValue().withS("New item!"));
                        dynamoDBClient.putItem(tableName, item);

                        // Update the item
                        Map<String, AttributeValue> key = new HashMap<>();
                        key.put("Id", new AttributeValue().withN(i.toString()));
                        Map<String, AttributeValueUpdate> attributeUpdates = new HashMap<>();
                        attributeUpdates.put("Message", new AttributeValueUpdate()
                                        .withAction(AttributeAction.PUT)
                                        .withValue(new AttributeValue()
                                                        .withS("This item has changed")));
                        dynamoDBClient.updateItem(tableName, key, attributeUpdates);

                        // Delete the item
                        dynamoDBClient.deleteItem(tableName, key);
                }

                // Get all the shard IDs from the stream. Note that DescribeStream returns
                // the shard IDs one page at a time.
                String lastEvaluatedShardId = null;

                do {
                        DescribeStreamResult describeStreamResult = streamsClient.describeStream(
                                        new DescribeStreamRequest()
                                                        .withStreamArn(streamArn)
                                                        .withExclusiveStartShardId(lastEvaluatedShardId));
                        List<Shard> shards = describeStreamResult.getStreamDescription().getShards();

                        // Process each shard on this page

                        for (Shard shard : shards) {
                                String shardId = shard.getShardId();
                                System.out.println("Shard: " + shard);

                                // Get an iterator for the current shard

                                GetShardIteratorRequest getShardIteratorRequest = new GetShardIteratorRequest()
                                                .withStreamArn(streamArn)
                                                .withShardId(shardId)
                                                .withShardIteratorType(ShardIteratorType.TRIM_HORIZON);
                                GetShardIteratorResult getShardIteratorResult = streamsClient
                                                .getShardIterator(getShardIteratorRequest);
                                String currentShardIter = getShardIteratorResult.getShardIterator();

                                // Shard iterator is not null until the Shard is sealed (marked as READ_ONLY).
                                // To prevent running the loop until the Shard is sealed, which will be on
                                // average
                                // 4 hours, we process only the items that were written into DynamoDB and then
                                // exit.
                                int processedRecordCount = 0;
                                while (currentShardIter != null && processedRecordCount < maxItemCount) {
                                        System.out.println("    Shard iterator: " + currentShardIter.substring(380));

                                        // Use the shard iterator to read the stream records

                                        GetRecordsResult getRecordsResult = streamsClient
                                                        .getRecords(new GetRecordsRequest()
                                                                        .withShardIterator(currentShardIter));
                                        List<Record> records = getRecordsResult.getRecords();
                                        for (Record record : records) {
                                                System.out.println("        " + record.getDynamodb());
                                        }
                                        processedRecordCount += records.size();
                                        currentShardIter = getRecordsResult.getNextShardIterator();
                                }
                        }

                        // If LastEvaluatedShardId is set, then there is
                        // at least one more page of shard IDs to retrieve
                        lastEvaluatedShardId = describeStreamResult.getStreamDescription().getLastEvaluatedShardId();

                } while (lastEvaluatedShardId != null);

                // Delete the table
                System.out.println("Deleting the table...");
                dynamoDBClient.deleteTable(tableName);

                System.out.println("Demo complete");

        }
}