DynamoDB Streams 하위 수준 API: Java 예시

참고

이 페이지의 코드는 완전한 코드가 아니며, Amazon DynamoDB Streams 사용 시나리오 중 일부만 처리합니다. DynamoDB에서 스트림 레코드를 사용하기 위해 권장되는 방법은 DynamoDB Streams Kinesis 어댑터를 사용하여 스트림 레코드 처리 단원에 기술된 것처럼 Amazon Kinesis 어댑터를 통해 Kinesis Client Library(KCL)를 사용하는 것입니다.

이 단원에는 실행 중인 DynamoDB Streams를 보여 주는 Java 프로그램이 나와 있습니다. 이 프로그램에서는 다음 작업을 수행합니다.

1. 스트림을 활성화하여 DynamoDB 테이블을 생성합니다.

2. 이 테이블의 스트림 설정을 설명합니다.

3. 테이블의 데이터를 수정합니다.

4. 스트림의 샤드를 설명합니다.

5. 샤드의 스트림 레코드를 읽습니다.

6. 그리고 정리합니다.

프로그램을 실행하면 다음과 비슷한 출력 화면이 나타납니다.

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

예

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");

        }
}