Gets an Amazon Kinesis shard iterator. A shard iterator expires 5 minutes after it is returned to the requester.
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.
A shard iterator specifies the shard position from which to start reading data records sequentially. The position is specified using the sequence number of a data record in a shard. A sequence number is the identifier associated with every record ingested in the stream, and is assigned when a record is put into the stream. Each stream has one or more shards.
You must specify the shard iterator type. For example, you can set the
ShardIteratorType parameter to read exactly from the position denoted by a specific sequence number by using the
AT_SEQUENCE_NUMBER shard iterator type. Alternatively, the parameter can read right after the sequence number by using the
AFTER_SEQUENCE_NUMBER shard iterator type, using sequence numbers returned by earlier calls to
PutRecord,
PutRecords,
GetRecords, or
DescribeStream. In the request, you can specify the shard iterator type
AT_TIMESTAMP to read records from an arbitrary point in time,
TRIM_HORIZON to cause
ShardIterator to point to the last untrimmed record in the shard in the system (the oldest data record in the shard), or
LATEST so that you always read the most recent data in the shard.
When you read repeatedly from a stream, use a
GetShardIterator request to get the first shard iterator for use in your first
GetRecords request and for subsequent reads use the shard iterator returned by the
GetRecords request in
NextShardIterator. A new shard iterator is returned by every
GetRecords request in
NextShardIterator, which you use in the
ShardIterator parameter of the next
GetRecords request.
If a
GetShardIterator request is made too often, you receive a
ProvisionedThroughputExceededException. For more information about throughput limits, see
GetRecords, and
Streams Limits in the
Amazon Kinesis Data Streams Developer Guide.
If the shard is closed,
GetShardIterator returns a valid iterator for the last sequence number of the shard. A shard can be closed as a result of using
SplitShard or
MergeShards.
GetShardIterator has a limit of five transactions per second per account per open shard.