Gets data records from a shard.

Specify a shard iterator using the ShardIterator parameter. The shard iterator specifies the position in the shard from which you want to start reading data records sequentially. If there are no records available in the portion of the shard that the iterator points to, GetRecords returns an empty list. Note that it might take multiple calls to get to a portion of the shard that contains records.

You can scale by provisioning multiple shards. Your application should have one thread per shard, each reading continuously from its stream. To read from a stream continually, call GetRecords in a loop. Use GetShardIterator to get the shard iterator to specify in the first GetRecords call. GetRecords returns a new shard iterator in NextShardIterator. Specify the shard iterator returned in NextShardIterator in subsequent calls to GetRecords. Note that if the shard has been closed, the shard iterator can't return more data and GetRecords returns null in NextShardIterator. You can terminate the loop when the shard is closed, or when the shard iterator reaches the record with the sequence number or other attribute that marks it as the last record to process.

Each data record can be up to 50 KB in size, and each shard can read up to 2 MB per second. You can ensure that your calls don't exceed the maximum supported size or throughput by using the Limit parameter to specify the maximum number of records that GetRecords can return. Consider your average record size when determining this limit. For example, if your average record size is 40 KB, you can limit the data returned to about 1 MB per call by specifying 25 as the limit.

The size of the data returned by GetRecords will vary depending on the utilization of the shard. The maximum size of data that GetRecords can return is 10 MB. If a call returns 10 MB of data, subsequent calls made within the next 5 seconds throw ProvisionedThroughputExceededException. If there is insufficient provisioned throughput on the shard, subsequent calls made within the next 1 second throw ProvisionedThroughputExceededException. Note that GetRecords won't return any data when it throws an exception. For this reason, we recommend that you wait one second between calls to GetRecords; however, it's possible that the application will get exceptions for longer than 1 second.

To detect whether the application is falling behind in processing, add a timestamp to your records and note how long it takes to process them. You can also monitor how much data is in a stream using the CloudWatch metrics for write operations (PutRecord and PutRecords). For more information, see Monitoring Amazon Kinesis with Amazon CloudWatch in the Amazon Kinesis Developer Guide.

http://docs.aws.amazon.com/kinesis/latest/APIReference/API_GetRecords.html