/AWS1/CL_KNS=>GETRECORDS()¶
About GetRecords¶
Gets data records from a Kinesis data stream's shard.
When invoking this API, you must use either the StreamARN or the
StreamName parameter, or both. It is recommended that you use the
StreamARN input parameter when you invoke this API.
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. It might
take multiple calls to get to a portion of the shard that contains records.
You can scale by provisioning multiple shards per stream while considering service
limits (for more information, see Amazon Kinesis Data Streams
Limits in the Amazon Kinesis Data Streams Developer
Guide). 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.
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 1 MiB in size, and each shard can read up to 2 MiB 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. The maximum number of records that can be returned per call
is 10,000.
The size of the data returned by GetRecords varies depending on the
utilization of the shard. It is recommended that consumer applications retrieve records
via the GetRecords command using the 5 TPS limit to remain caught up.
Retrieving records less frequently can lead to consumer applications falling behind. The
maximum size of data that GetRecords can return is 10 MiB. If a call
returns this amount of data, subsequent calls made within the next 5 seconds throw
ProvisionedThroughputExceededException. If there is insufficient
provisioned throughput on the stream, subsequent calls made within the next 1 second
throw ProvisionedThroughputExceededException. GetRecords
doesn't return any data when it throws an exception. For this reason, we recommend that
you wait 1 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, you can use the
MillisBehindLatest response attribute. You can also monitor the stream
using CloudWatch metrics and other mechanisms (see Monitoring in the Amazon
Kinesis Data Streams Developer Guide).
Each Amazon Kinesis record includes a value, ApproximateArrivalTimestamp,
that is set when a stream successfully receives and stores a record. This is commonly
referred to as a server-side time stamp, whereas a client-side time stamp is set when a
data producer creates or sends the record to a stream (a data producer is any data
source putting data records into a stream, for example with PutRecords). The time stamp has millisecond precision. There are no guarantees about the time
stamp accuracy, or that the time stamp is always increasing. For example, records in a
shard or across a stream might have time stamps that are out of order.
This operation has a limit of five transactions per second per shard.
Method Signature¶
IMPORTING¶
Required arguments:¶
IV_SHARDITERATOR TYPE /AWS1/KNSSHARDITERATOR /AWS1/KNSSHARDITERATOR¶
The position in the shard from which you want to start sequentially reading data records. A shard iterator specifies this position using the sequence number of a data record in the shard.
Optional arguments:¶
IV_LIMIT TYPE /AWS1/KNSGETRECORDSINPUTLIMIT /AWS1/KNSGETRECORDSINPUTLIMIT¶
The maximum number of records to return. Specify a value of up to 10,000. If you specify a value that is greater than 10,000, GetRecords throws
InvalidArgumentException. The default value is 10,000.
IV_STREAMARN TYPE /AWS1/KNSSTREAMARN /AWS1/KNSSTREAMARN¶
The ARN of the stream.