Dynamodb WriteRequestBatch的AWS PHP SDK问题

Question

I am experimenting with WriteRequestBatch from AWS SDK for Dynamodb. Below is my code. Everything works except the WriteRequestBatch part. I have no clue why, and was wondering if the community could help me out here. What might I be doing wrong? I have tried googling and searching here and found only 8 other questions that could be related but unfortunately were of no help.

This is where I started from.

$ddb_client = DynamoDbClient::factory(array(
    'region' => 'us-east-1',
    'key' => 'my_key',
    'secret' => 'my_secret'
));

$ddb_client->createTable(array(
    'TableName' => 'my_table',
    'AttributeDefinitions' => array(
        array(
            'AttributeName' => 'id',
            'AttributeType' => 'S'
        ),
        array(
            'AttributeName' => 'ns',
            'AttributeType' => 'S'
        )
    ),
    'KeySchema' => array(
        array(
            'AttributeName' => 'id',
            'KeyType'       => 'HASH'
        ),
        array(
            'AttributeName' => 'ns',
            'KeyType'       => 'RANGE'
        )
    ),
    'ProvisionedThroughput' => array(
        'ReadCapacityUnits'  => 10,
        'WriteCapacityUnits' => 10
    )
));

$response = $ddb_client->putItem(array(
    "TableName" => "my_table",
    "Item" => array(
        "id" => array("S" => "exp_id"),
        "ns" => array("S" => "exp_ns"),
        "version" => array("N" => "0"),
    ),
));

$item = $response['Item'];
$item['version']['N'] = '1';

$put_batch = WriteRequestBatch::factory($ddb_client);
$put_request = new PutRequest(
    array(
        "Item" => $item,
        "Expected" => array(
            "version" => array(
                "ComparisonOperator" => "EQ",
                "AttributeValueList" => array(
                    array("N" => "0")
                )
            ),
        ),
    ),
    "my_table"
);
$putBatch->add($put_request);
$putBatch->flush();

This works instead of WriteRequestBatch. I will just have to manage batches to put myself than use WriteRequestBatch doing it for me:

$response = $ddb_client->batchWriteItem(array(
    "RequestItems" => array(
        "my_table" => array(
            array(
                "PutRequest" => array(
                    "Item" => $item,
                    "Expected" => array(
                        "version" => array(
                            "ComparisonOperator" => "EQ",
                            "AttributeValueList" => array(
                                array("S" => "0")
                            )
                        ),
                    ),
                )
            )
        )
    )
));

Answer 1

Because you currently do not have any "try / catch" error handling around your code you are likely not getting good information on your error.

I placed try/catch blocks on your code and found that the table creates just fine but that the call to putItem fails for the following reason: Requested resource not found

When you create a table it is NOT immediately available. You have to pause until it becomes available. This paragraph of the AWS docs explains this nicely:

CreateTable is an asynchronous operation. Upon receiving a CreateTable request, DynamoDB immediately returns a response with a TableStatus of CREATING . After the table is created, DynamoDB sets the TableStatus to ACTIVE . You can perform read and write operations only on an ACTIVE table. You can use the DescribeTable API to check the table status.

Once you add the call to DescribeTable like it shows, you should be good.

Answer 2

The answer by Geek Stocks is incomplete, but still helpful. One thing you can do handle the asynchronous aspects of the CreateTable operation is to use a Waiter :

$ddb_client->createTable(array('TableName' => 'my_table', ... ));
$ddb_client->waitUntil('TableExists', array('TableName' => 'my_table'));

However , there is also a problem with how you are using the WriteRequestBatch class. When you create a PutRequest , you must pass in the item, not a whole set of PutItem parameters. The WriteRequestBatch is an abstraction over DynamoDB's BatchWriteItem operation , which does not allow things like the Expected parameter. If you want to do that, then you need to use individual PutItem / UpdateItem / DeleteItem requests.

Here is a modified version of your usage of WriteRequestBatch that is correct:

$putBatch = WriteRequestBatch::factory($ddb_client);
$putBatch->add(new PutRequest($item, 'my_table'));
// ADD MORE...
// ...
// ...
$putBatch->flush();

Here is another example of using the WriteRequestBatch from the SDK's User Guide.

---

EDIT : One more complete example that works that I just tested, that shows the difference between versions prior to 2.7.0 and afterwards

use Aws\DynamoDb\DynamoDbClient;
use Aws\DynamoDb\Model\BatchRequest\WriteRequestBatch;
use Aws\DynamoDb\Model\BatchRequest\PutRequest;
use Aws\DynamoDb\Model\Item;

$client = DynamoDbClient::factory([/* ... */]);
$batch = WriteRequestBatch::factory($client);
for ($i = 1; $i <= 55; $i++) {
    // FOR ANY SDK VERSION
    // (NOTE: Does not support new M, L, BOOL, and NULL types)
    $item = Item::fromArray(['id' => $i, 'data' => "foo{$i}"]);
    // FOR SDK >= 2.7
    $item = ['id' => ['N' => $i], 'data' => ['S' => "foo{$i}"]];

    $batch->add(new PutRequest($item, 'my-table'));
}
$batch->flush();