Java tutorial
/* * Copyright 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Licensed under the Amazon Software License (the "License"). * You may not use this file except in compliance with the License. * A copy of the License is located at * * http://aws.amazon.com/asl/ * * or in the "license" file accompanying this file. This file is distributed * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either * express or implied. See the License for the specific language governing * permissions and limitations under the License. */ package eu.roschi.obdkinesis.utils; import java.util.ArrayList; import java.util.List; import java.util.concurrent.TimeUnit; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.amazonaws.AmazonClientException; import com.amazonaws.services.dynamodbv2.AmazonDynamoDB; import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapper; import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperConfig; import com.amazonaws.services.dynamodbv2.datamodeling.DynamoDBMapperConfig.TableNameOverride; import com.amazonaws.services.dynamodbv2.model.AttributeDefinition; import com.amazonaws.services.dynamodbv2.model.CreateTableRequest; 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.ResourceInUseException; import com.amazonaws.services.dynamodbv2.model.ResourceNotFoundException; import com.amazonaws.services.dynamodbv2.model.ScalarAttributeType; /** * Utility methods for interacting with Amazon DynamoDB for this application. */ public class DynamoDBUtils { private static final Log LOG = LogFactory.getLog(DynamoDBUtils.class); private static final String ATTRIBUTE_NAME_HASH_KEY = "resource"; private static final String ATTRIBUTE_NAME_RANGE_KEY = "timestamp"; private AmazonDynamoDB dynamoDB; /** * Create a new utility instance that uses the provided Amazon DynamoDB client. * * @param dynamoDB The Amazon DynamoDB client to use. */ public DynamoDBUtils(AmazonDynamoDB dynamoDB) { if (dynamoDB == null) { throw new NullPointerException("dynamoDB must not be null"); } this.dynamoDB = dynamoDB; } /** * Create a DynamoDB mapper that uses the provided table name in every request. * * @param tableName The name of the DynamoDB table the mapper will use for all requests. * @return A mapper capable of reading/writing to the table given. */ public DynamoDBMapper createMapperForTable(String tableName) { DynamoDBMapperConfig config = new DynamoDBMapperConfig( TableNameOverride.withTableNameReplacement(tableName)); return new DynamoDBMapper(dynamoDB, config); } /** * Creates the table to store our counts in with a hash key of "resource" and a range key of "timestamp" so we can * query counts for a given resource by time. This uses an initial provisioned throughput of 10 read capacity units * and 5 write capacity units * * @param tableName The name of the table to create. */ public void createCountTableIfNotExists(String tableName) { List<KeySchemaElement> ks = new ArrayList<>(); ks.add(new KeySchemaElement().withKeyType(KeyType.HASH).withAttributeName(ATTRIBUTE_NAME_HASH_KEY)); ks.add(new KeySchemaElement().withKeyType(KeyType.RANGE).withAttributeName(ATTRIBUTE_NAME_RANGE_KEY)); ArrayList<AttributeDefinition> attributeDefinitions = new ArrayList<>(); attributeDefinitions.add(new AttributeDefinition().withAttributeName(ATTRIBUTE_NAME_HASH_KEY) .withAttributeType(ScalarAttributeType.S)); // Range key must be a String. DynamoDBMapper translates Dates to ISO8601 strings. attributeDefinitions.add(new AttributeDefinition().withAttributeName(ATTRIBUTE_NAME_RANGE_KEY) .withAttributeType(ScalarAttributeType.S)); // Create the table with enough write IOPS to handle 5 distinct resources updated every 1 second: // 1 update/second * 5 resources = 5 write IOPS. // The provisioned throughput will need to be adjusted if the cadinality of the input data or the interval for // updates changes. CreateTableRequest createTableRequest = new CreateTableRequest().withTableName(tableName) .withProvisionedThroughput(new ProvisionedThroughput(1L, 1L)).withKeySchema(ks) .withAttributeDefinitions(attributeDefinitions); try { dynamoDB.createTable(createTableRequest); LOG.info(String.format("Created DynamoDB table: %s. Waiting up to 5 minutes for it to become ACTIVE...", tableName)); // Wait 5 minutes for the table to become ACTIVE if (!waitUntilTableIsActive(tableName, 10, TimeUnit.MINUTES.toSeconds(5))) { throw new IllegalStateException( String.format("Timed out while waiting for DynamoDB table %s to become ready", tableName)); } } catch (ResourceInUseException ex) { // Assume table exists and is ready to use } } /** * Delete a DynamoDB table. * * @param tableName The name of the table to delete. */ public void deleteTable(String tableName) { LOG.info(String.format("Deleting DynamoDB table %s", tableName)); try { dynamoDB.deleteTable(tableName); } catch (ResourceNotFoundException ex) { // Ignore, table could not be found. } catch (AmazonClientException ex) { LOG.error(String.format("Error deleting DynamoDB table %s", tableName), ex); } } /** * Wait for a DynamoDB table to become active and ready for use. * * @param tableName The name of the table to wait until it becomes active. * @param secondsBetweenPolls Seconds to wait between requests to DynamoDB. * @param timeoutSeconds Maximum amount of time, in seconds, to wait for a table to become ready. * @return {@code true} if the table is ready. False if our timeout exceeded or we were interrupted. */ private boolean waitUntilTableIsActive(String tableName, long secondsBetweenPolls, long timeoutSeconds) { long sleepTimeRemaining = timeoutSeconds * 1000; while (!doesTableExist(tableName)) { if (sleepTimeRemaining <= 0) { return false; } long timeToSleepMillis = Math.min(1000 * secondsBetweenPolls, sleepTimeRemaining); try { Thread.sleep(timeToSleepMillis); } catch (InterruptedException ex) { LOG.warn("Interrupted while waiting for count table to become ready", ex); Thread.currentThread().interrupt(); return false; } sleepTimeRemaining -= timeToSleepMillis; } return true; } /** * Determines if the table exists and is ACTIVE. * * @param tableName The name of the table to check. * @return {@code true} if the table exists and is in the ACTIVE state */ private boolean doesTableExist(String tableName) { try { return "ACTIVE".equals(dynamoDB.describeTable(tableName).getTable().getTableStatus()); } catch (AmazonClientException ex) { LOG.warn(String.format("Unable to describe table %s", tableName), ex); return false; } } }