Copyright | (c) 2013-2016 Brendan Hay |
---|---|
License | Mozilla Public License, v. 2.0. |
Maintainer | Brendan Hay <brendan.g.hay@gmail.com> |
Stability | auto-generated |
Portability | non-portable (GHC extensions) |
Safe Haskell | None |
Language | Haskell2010 |
Gets data records from an Amazon Kinesis stream's 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 per stream while considering service limits (for more information, see Streams Limits in the Amazon Kinesis 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
. 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 1 MB 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.
The size of the data returned by GetRecords
varies 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 stream using CloudWatch metrics and other mechanisms (see Monitoring in the Amazon Kinesis 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 timestamp, whereas a client-side timestamp 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 timestamp has millisecond precision. There are no guarantees about the timestamp accuracy, or that the timestamp is always increasing. For example, records in a shard or across a stream might have timestamps that are out of order.
- getRecords :: Text -> GetRecords
- data GetRecords
- grLimit :: Lens' GetRecords (Maybe Natural)
- grShardIterator :: Lens' GetRecords Text
- getRecordsResponse :: Int -> GetRecordsResponse
- data GetRecordsResponse
- grrsNextShardIterator :: Lens' GetRecordsResponse (Maybe Text)
- grrsMillisBehindLatest :: Lens' GetRecordsResponse (Maybe Natural)
- grrsResponseStatus :: Lens' GetRecordsResponse Int
- grrsRecords :: Lens' GetRecordsResponse [Record]
Creating a Request
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
- 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
throwsInvalidArgumentException
.grShardIterator
- 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.
data GetRecords Source #
Represents the input for GetRecords
.
See: getRecords
smart constructor.
Request Lenses
grLimit :: Lens' GetRecords (Maybe Natural) Source #
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 Source #
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
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:
grrsNextShardIterator
- The next position in the shard from which to start sequentially reading data records. If set tonull
, the shard has been closed and the requested iterator will not return any more data.grrsMillisBehindLatest
- The number of milliseconds theGetRecords
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.grrsResponseStatus
- -- | The response status code.grrsRecords
- The data records retrieved from the shard.
data GetRecordsResponse Source #
Represents the output for GetRecords
.
See: getRecordsResponse
smart constructor.
Response Lenses
grrsNextShardIterator :: Lens' GetRecordsResponse (Maybe Text) Source #
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.
grrsMillisBehindLatest :: Lens' GetRecordsResponse (Maybe Natural) Source #
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.
grrsResponseStatus :: Lens' GetRecordsResponse Int Source #
- - | The response status code.
grrsRecords :: Lens' GetRecordsResponse [Record] Source #
The data records retrieved from the shard.