MongoDB -> DynamoDB Migration - php

Question

All,
I am attempting to migrate roughly 6GB of Mongo data that is comprised of hundreds of collections to DynamoDB. I have written some scripts using the AWS PHP SDK and am able to port over very small collections but when I try ones that have more than 20k documents (still a very small collection all things considered) it either takes an outrageous amount of time or quietly fails.
Does anyone have some tips/tricks for taking data from Mongo (or any other NoSQL DB) and migrating it to Dynamo, or any other NoSQL DB. I feel like this should be relatively easy because the documents are extremely flat/simple.
Any thoughts/suggestions would be much appreciated!
Thanks!
header.php
<?
require './aws-autoloader.php';
require './MongoGet.php';
set_time_limit(0);
use \Aws\DynamoDb\DynamoDbClient;
$client = \Aws\DynamoDb\DynamoDbClient::factory(array(
'key' => 'MY_KEY',
'secret' => 'MY_SECRET',
'region' => 'MY_REGION',
'base_url' => 'http://localhost:8000'
));
$collection = "AccumulatorGasPressure4093_raw";
function nEcho($str) {
echo "{$str}<br>\n";
}
echo "<pre>";
test-store.php
<?
include('test-header.php');
nEcho("Creating table(s)...");
// create test table
$client->createTable(array(
'TableName' => $collection,
'AttributeDefinitions' => array(
array(
'AttributeName' => 'id',
'AttributeType' => 'N'
),
array(
'AttributeName' => 'count',
'AttributeType' => 'N'
)
),
'KeySchema' => array(
array(
'AttributeName' => 'id',
'KeyType' => 'HASH'
),
array(
'AttributeName' => 'count',
'KeyType' => 'RANGED'
)
),
'ProvisionedThroughput' => array(
'ReadCapacityUnits' => 10,
'WriteCapacityUnits' => 20
)
));
$result = $client->describeTable(array(
'TableName' => $collection
));
nEcho("Done creating table...");
nEcho("Getting data from Mongo...");
// instantiate class and get data
$mGet = new MongoGet();
$results = $mGet->getData($collection);
nEcho ("Done retrieving Mongo data...");
nEcho ("Inserting data...");
$i = 0;
foreach($results as $result) {
$insertResult = $client->putItem(array(
'TableName' => $collection,
'Item' => $client->formatAttributes(array(
'id' => $i,
'date' => $result['date'],
'value' => $result['value'],
'count' => $i
)),
'ReturnConsumedCapacity' => 'TOTAL'
));
$i++;
}
nEcho("Done Inserting, script ending...");

Answer 1

I suspect that you are being throttled by DynamoDB, especially if your tables' throughputs are low. The SDK retries the requests, up to 11 times per request, but eventually, the requests fail, which should throw an exception.
You should take a look at the WriteRequestBatch object. This object is basically a queue of items that get sent in batches, but any items that fail to transfer are re-queued automatically. Should provide a more robust solution for what you are doing.