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The AWS Java SDK for Amazon DynamoDB module holds the client classes that are used for communicating with Amazon DynamoDB Service
/*
* Copyright 2013-2016 Amazon Technologies, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://aws.amazon.com/apache2.0
*
* 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 com.amazonaws.services.dynamodbv2.util;
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.model.CreateTableRequest;
import com.amazonaws.services.dynamodbv2.model.DeleteTableRequest;
import com.amazonaws.services.dynamodbv2.model.DescribeTableRequest;
import com.amazonaws.services.dynamodbv2.model.ResourceInUseException;
import com.amazonaws.services.dynamodbv2.model.ResourceNotFoundException;
import com.amazonaws.services.dynamodbv2.model.TableDescription;
import com.amazonaws.services.dynamodbv2.model.TableStatus;
/**
* Utility methods for working with DynamoDB tables.
*
*
* // ... create DynamoDB table ...
* try {
* waitUntilActive(dynamoDB, myTableName());
* } catch (AmazonClientException e) {
* // table didn't become active
* }
* // ... start making calls to table ...
*
*/
public class TableUtils {
/**
* Thrown by {@link TableUtils} when a table never reaches a desired state
*/
public static class TableNeverTransitionedToStateException extends AmazonClientException {
private static final long serialVersionUID = 8920567021104846647L;
public TableNeverTransitionedToStateException(String tableName, TableStatus desiredStatus) {
super("Table " + tableName + " never transitioned to desired state of " + desiredStatus.toString());
}
}
private static final int DEFAULT_WAIT_TIMEOUT = 10 * 60 * 1000;
private static final int DEFAULT_WAIT_INTERVAL = 20 * 1000;
/**
* The logging utility.
*/
private static final Log LOG = LogFactory.getLog(TableUtils.class);
/**
* Waits up to 10 minutes for a specified DynamoDB table to resolve,
* indicating that it exists. If the table doesn't return a result after
* this time, an AmazonClientException is thrown.
*
* @param dynamo
* The DynamoDB client to use to make requests.
* @param tableName
* The name of the table being resolved.
*
* @throws AmazonClientException
* If the specified table does not resolve before this method
* times out and stops polling.
* @throws InterruptedException
* If the thread is interrupted while waiting for the table to
* resolve.
*/
public static void waitUntilExists(final AmazonDynamoDB dynamo, final String tableName)
throws InterruptedException {
waitUntilExists(dynamo, tableName, DEFAULT_WAIT_TIMEOUT, DEFAULT_WAIT_INTERVAL);
}
/**
* Waits up to a specified amount of time for a specified DynamoDB table to
* resolve, indicating that it exists. If the table doesn't return a result
* after this time, an AmazonClientException is thrown.
*
* @param dynamo
* The DynamoDB client to use to make requests.
* @param tableName
* The name of the table being resolved.
* @param timeout
* The maximum number of milliseconds to wait.
* @param interval
* The poll interval in milliseconds.
*
* @throws AmazonClientException
* If the specified table does not resolve before this method
* times out and stops polling.
* @throws InterruptedException
* If the thread is interrupted while waiting for the table to
* resolve.
*/
public static void waitUntilExists(final AmazonDynamoDB dynamo, final String tableName, final int timeout,
final int interval) throws InterruptedException {
TableDescription table = waitForTableDescription(dynamo, tableName, null, timeout, interval);
if (table == null) {
throw new AmazonClientException("Table " + tableName + " never returned a result");
}
}
/**
* Waits up to 10 minutes for a specified DynamoDB table to move into the
* ACTIVE state. If the table does not exist or does not
* transition to the ACTIVE state after this time, then an
* AmazonClientException is thrown.
*
* @param dynamo
* The DynamoDB client to use to make requests.
* @param tableName
* The name of the table whose status is being checked.
*
* @throws TableNeverTransitionedToStateException
* If the specified table does not exist or does not transition
* into the ACTIVE state before this method times
* out and stops polling.
* @throws InterruptedException
* If the thread is interrupted while waiting for the table to
* transition into the ACTIVE state.
*/
public static void waitUntilActive(final AmazonDynamoDB dynamo, final String tableName)
throws InterruptedException, TableNeverTransitionedToStateException {
waitUntilActive(dynamo, tableName, DEFAULT_WAIT_TIMEOUT, DEFAULT_WAIT_INTERVAL);
}
/**
* Waits up to a specified amount of time for a specified DynamoDB table to
* move into the ACTIVE state. If the table does not exist or
* does not transition to the ACTIVE state after this time,
* then an AmazonClientException is thrown.
*
* @param dynamo
* The DynamoDB client to use to make requests.
* @param tableName
* The name of the table whose status is being checked.
* @param timeout
* The maximum number of milliseconds to wait.
* @param interval
* The poll interval in milliseconds.
*
* @throws TableNeverTransitionedToStateException
* If the specified table does not exist or does not transition
* into the ACTIVE state before this method times
* out and stops polling.
* @throws InterruptedException
* If the thread is interrupted while waiting for the table to
* transition into the ACTIVE state.
*/
public static void waitUntilActive(final AmazonDynamoDB dynamo, final String tableName, final int timeout,
final int interval) throws InterruptedException, TableNeverTransitionedToStateException {
TableDescription table = waitForTableDescription(dynamo, tableName, TableStatus.ACTIVE, timeout, interval);
if (table == null || !table.getTableStatus().equals(TableStatus.ACTIVE.toString())) {
throw new TableNeverTransitionedToStateException(tableName, TableStatus.ACTIVE);
}
}
/**
* Wait for the table to reach the desired status and returns the table
* description
*
* @param dynamo
* Dynamo client to use
* @param tableName
* Table name to poll status of
* @param desiredStatus
* Desired {@link TableStatus} to wait for. If null this method
* simply waits until DescribeTable returns something non-null
* (i.e. any status)
* @param timeout
* Timeout in milliseconds to continue to poll for desired status
* @param interval
* Time to wait in milliseconds between poll attempts
* @return Null if DescribeTables never returns a result, otherwise the
* result of the last poll attempt (which may or may not have the
* desired state)
* @throws InterruptedException
* @throws {@link
* IllegalArgumentException} If timeout or interval is invalid
*/
private static TableDescription waitForTableDescription(final AmazonDynamoDB dynamo, final String tableName,
TableStatus desiredStatus, final int timeout, final int interval)
throws InterruptedException, IllegalArgumentException {
if (timeout < 0) {
throw new IllegalArgumentException("Timeout must be >= 0");
}
if (interval <= 0 || interval >= timeout) {
throw new IllegalArgumentException("Interval must be > 0 and < timeout");
}
long startTime = System.currentTimeMillis();
long endTime = startTime + timeout;
TableDescription table = null;
while (System.currentTimeMillis() < endTime) {
try {
table = dynamo.describeTable(new DescribeTableRequest(tableName)).getTable();
if (desiredStatus == null || table.getTableStatus().equals(desiredStatus.toString())) {
return table;
}
} catch (ResourceNotFoundException rnfe) {
// ResourceNotFound means the table doesn't exist yet,
// so ignore this error and just keep polling.
}
Thread.sleep(interval);
}
return table;
}
/**
* Creates the table and ignores any errors if it already exists.
* @param dynamo The Dynamo client to use.
* @param createTableRequest The create table request.
* @return True if created, false otherwise.
*/
public static final boolean createTableIfNotExists(final AmazonDynamoDB dynamo, final CreateTableRequest createTableRequest) {
try {
dynamo.createTable(createTableRequest);
return true;
} catch (final ResourceInUseException e) {
if (LOG.isTraceEnabled()) {
LOG.trace("Table " + createTableRequest.getTableName() + " already exists", e);
}
}
return false;
}
/**
* Deletes the table and ignores any errors if it doesn't exist.
* @param dynamo The Dynamo client to use.
* @param deleteTableRequest The delete table request.
* @return True if deleted, false otherwise.
*/
public static final boolean deleteTableIfExists(final AmazonDynamoDB dynamo, final DeleteTableRequest deleteTableRequest) {
try {
dynamo.deleteTable(deleteTableRequest);
return true;
} catch (final ResourceNotFoundException e) {
if (LOG.isTraceEnabled()) {
LOG.trace("Table " + deleteTableRequest.getTableName() + " does not exist", e);
}
}
return false;
}
}
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