Network.AWS.Kinesis.GetRecords

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 this amount 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, you can use the MillisBehindLatest response attribute. You can also monitor the amount of data in a stream using the CloudWatch metrics. For more information, see Monitoring Amazon Kinesis with Amazon CloudWatch in the Amazon Kinesis Developer Guide.

See: AWS API Reference for GetRecords.

Creating a Request

getRecords

Arguments

:: Text

grShardIterator

-> GetRecords

Creates a value of GetRecords with the minimum fields required to make a request.

Use one of the following lenses to modify other fields as desired:

• grLimit
• grShardIterator

data GetRecords

Represents the input for GetRecords.

See: getRecords smart constructor.

Instances

Eq GetRecords

Data GetRecords

Read GetRecords

Show GetRecords

Generic GetRecords

ToJSON GetRecords

AWSRequest GetRecords

ToPath GetRecords

ToHeaders GetRecords

ToQuery GetRecords

type Rep GetRecords

type Sv GetRecords = Kinesis

type Rs GetRecords = GetRecordsResponse

Request Lenses

grLimit :: Lens' GetRecords (Maybe Natural)

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.

grShardIterator :: Lens' GetRecords Text

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.

Destructuring the Response

getRecordsResponse

Arguments

:: Int

grrsStatus

-> GetRecordsResponse

Creates a value of GetRecordsResponse with the minimum fields required to make a request.

Use one of the following lenses to modify other fields as desired:

• grrsMillisBehindLatest
• grrsNextShardIterator
• grrsStatus
• grrsRecords

data GetRecordsResponse

Represents the output for GetRecords.

See: getRecordsResponse smart constructor.

Instances

Eq GetRecordsResponse

Data GetRecordsResponse

Read GetRecordsResponse

Show GetRecordsResponse

Generic GetRecordsResponse

type Rep GetRecordsResponse

Response Lenses

grrsMillisBehindLatest :: Lens' GetRecordsResponse (Maybe Natural)

The number of milliseconds the GetRecords response is from the tip of the stream, indicating how far behind current time the consumer is. A value of zero indicates record processing is caught up, and there are no new records to process at this moment.

grrsNextShardIterator :: Lens' GetRecordsResponse (Maybe Text)

The next position in the shard from which to start sequentially reading data records. If set to null, the shard has been closed and the requested iterator will not return any more data.

grrsStatus :: Lens' GetRecordsResponse Int

The response status code.

grrsRecords :: Lens' GetRecordsResponse [Record]

The data records retrieved from the shard.