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Amazon Kinesis Streams Service API Reference
API Reference (API Version 2013-12-02)

GetShardIterator

Gets an Amazon Kinesis shard iterator. A shard iterator expires five minutes after it is returned to the requester.

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, or 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 Streams Developer Guide.

If the shard is closed, GetShardIterator returns a valid iterator for the last sequence number of the shard. Note that a shard can be closed as a result of using SplitShard or MergeShards.

GetShardIterator has a limit of 5 transactions per second per account per open shard.

Request Syntax

{
   "ShardId": "string",
   "ShardIteratorType": "string",
   "StartingSequenceNumber": "string",
   "StreamName": "string",
   "Timestamp": number
}

Request Parameters

The request accepts the following data in JSON format.

ShardId

The shard ID of the Amazon Kinesis shard to get the iterator for.

Type: String

Length Constraints: Minimum length of 1. Maximum length of 128.

Pattern: [a-zA-Z0-9_.-]+

Required: Yes

ShardIteratorType

Determines how the shard iterator is used to start reading data records from the shard.

The following are the valid Amazon Kinesis shard iterator types:

  • AT_SEQUENCE_NUMBER - Start reading from the position denoted by a specific sequence number, provided in the value StartingSequenceNumber.

  • AFTER_SEQUENCE_NUMBER - Start reading right after the position denoted by a specific sequence number, provided in the value StartingSequenceNumber.

  • AT_TIMESTAMP - Start reading from the position denoted by a specific timestamp, provided in the value Timestamp.

  • TRIM_HORIZON - Start reading at the last untrimmed record in the shard in the system, which is the oldest data record in the shard.

  • LATEST - Start reading just after the most recent record in the shard, so that you always read the most recent data in the shard.

Type: String

Valid Values: AT_SEQUENCE_NUMBER | AFTER_SEQUENCE_NUMBER | TRIM_HORIZON | LATEST | AT_TIMESTAMP

Required: Yes

StartingSequenceNumber

The sequence number of the data record in the shard from which to start reading. Used with shard iterator type AT_SEQUENCE_NUMBER and AFTER_SEQUENCE_NUMBER.

Type: String

Pattern: 0|([1-9]\d{0,128})

Required: No

StreamName

The name of the Amazon Kinesis stream.

Type: String

Length Constraints: Minimum length of 1. Maximum length of 128.

Pattern: [a-zA-Z0-9_.-]+

Required: Yes

Timestamp

The timestamp of the data record from which to start reading. Used with shard iterator type AT_TIMESTAMP. A timestamp is the Unix epoch date with precision in milliseconds. For example, 2016-04-04T19:58:46.480-00:00 or 1459799926.480. If a record with this exact timestamp does not exist, the iterator returned is for the next (later) record. If the timestamp is older than the current trim horizon, the iterator returned is for the oldest untrimmed data record (TRIM_HORIZON).

Type: Timestamp

Required: No

Response Syntax

{
   "ShardIterator": "string"
}

Response Elements

If the action is successful, the service sends back an HTTP 200 response.

The following data is returned in JSON format by the service.

ShardIterator

The position in the shard from which to start reading data records sequentially. A shard iterator specifies this position using the sequence number of a data record in a shard.

Type: String

Length Constraints: Minimum length of 1. Maximum length of 512.

Errors

For information about the errors that are common to all actions, see Common Errors.

InvalidArgumentException

A specified parameter exceeds its restrictions, is not supported, or can't be used. For more information, see the returned message.

HTTP Status Code: 400

ProvisionedThroughputExceededException

The request rate for the stream is too high, or the requested data is too large for the available throughput. Reduce the frequency or size of your requests. For more information, see Streams Limits in the Amazon Kinesis Streams Developer Guide, and Error Retries and Exponential Backoff in AWS in the AWS General Reference.

HTTP Status Code: 400

ResourceNotFoundException

The requested resource could not be found. The stream might not be specified correctly.

HTTP Status Code: 400

Example

To get a shard iterator

The following JSON example gets the specified shard iterator.

Sample Request

POST / HTTP/1.1
Host: kinesis.<region>.<domain>
Content-Length: <PayloadSizeBytes>
User-Agent: <UserAgentString>
Content-Type: application/x-amz-json-1.1
Authorization: <AuthParams>
Connection: Keep-Alive 
X-Amz-Date: <Date>
X-Amz-Target: Kinesis_20131202.GetShardIterator
{
  "StreamName": "exampleStreamName",
  "ShardId": "shardId-000000000001",
  "ShardIteratorType": "LATEST"
}

Sample Response

HTTP/1.1 200 OK
x-amzn-RequestId: <RequestId>
Content-Type: application/x-amz-json-1.1
Content-Length: <PayloadSizeBytes>
Date: <Date> 
{
  "ShardIterator": "AAAAAAAAAAETYyAYzd665+8e0X7JTsASDM/Hr2rSwc0X2qz93iuA3udrjTH+ikQvpQk/1ZcMMLzRdAesqwBGPnsthzU0/CBlM/U8/8oEqGwX3pKw0XyeDNRAAZyXBo3MqkQtCpXhr942BRTjvWKhFz7OmCb2Ncfr8Tl2cBktooi6kJhr+djN5WYkB38Rr3akRgCl9qaU4dY="  
}